Block T-cell Proliferation Research Articles

Abstract 279: Iatrogenic immunosuppression emplaces tacrolimus to drive squamous skin cancer progression and influence the microenvironment

Abstract One in thirteen organ transplant recipients (OTRs) develop post-transplant cutaneous squamous cell carcinoma (cSCC), leading to significant morbidity upon disease progression. Although chronic ultraviolet (UV) exposure primarily underlies keratinocyte carcinogenesis, long-term immunosuppression is a critical etiologic risk factor due to reduced systemic surveillance of dysplasia. Calcineurin inhibitors such as tacrolimus are commonly administered to suppress the immune system by blocking T-cell proliferation and preventing donor organ rejection. Contrarily, studies have evinced the off-target effects of immunosuppressives, namely azathioprine and cyclosporine, but not tacrolimus — the most widely used in all immunosuppression. In addition, the preclinical research literature has overlooked the contribution of stromal fibroblasts in the cSCC tumor microenvironment (TME). Hence, we hypothesize that tacrolimus exerts direct carcinogenic effects on keratinocytes and fibroblasts in the skin. We further postulate that tacrolimus enables a tumor-permissive microenvironment by activating dermal fibroblasts to cause aggressive and invasive keratinocyte carcinoma in OTRs. To examine this cellular crosstalk phenomenon, we used human keratinocytes, primary dermal fibroblasts and cSCC cells in mono- and co-cultures to mimic cutaneous and tumor complexities. Next, we assessed the molecular mechanisms utilized by tacrolimus to potentiate tumorigenesis pertinent to cell survival, proliferation and invasion. Herein, we show that tacrolimus promotes cell survival dose-dependently in cSCC cells. We also found that a fibroblast-cSCC spheroid co-culture significantly enhances cell invasion. In a wound-healing migration assay, tacrolimus increased the migratory capacity of normal keratinocytes and cSCC cells. However, cell proliferation remains nebulous due to cyclical dose-response effects in vitro. We then queried whether cell proliferation is affected in vivo using immunodeficient mice, and similar results were observed. We confirmed via immunoblotting that tacrolimus induced elevated expression of proliferation markers at distinct drug concentrations. Altogether, our findings illuminate keratinocyte-stroma interactions and particularly isolate the contributory role of tacrolimus in non-immune mediated cSCC pathogenesis. This knowledge suggests newer immunosuppressives that do not inhibit calcineurin activity may help relieve cutaneous malignancies in transplant recipients. Citation Format: Edwin Kumah, Yash Chhabra, Vania Wang, Agrani Dixit, Ashani Weeraratna, Kristin Bibee. Iatrogenic immunosuppression emplaces tacrolimus to drive squamous skin cancer progression and influence the microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 279.

Combinatorial inhibition of Tec kinases BTK and ITK is beneficial in ameliorating murine sclerodermatous chronic graft versus host disease.

Graft-versus-host disease (GVHD) is the major factor limiting the widespread use of potentially curative allogeneic hematopoietic stem cell transplant (allo-HSCT). Chronic GVHD is characterized by the activation of alloreactive donor immune cells, especially B- and T-cells, leading to tissue damage and pathogenic fibrosis. In this study, we used highly specific next-generation inhibitors of ITK (PCYC-274), BTK (PCYC-804), and ibrutinib-like BTK/ITK inhibitors (PCYC-914 and PCYC-401) in the B10.D2 → BALB/C model of murine sclerodermatous cGVHD. From the third week onward, allogeneic recipients in each group of respective Tec kinase inhibitors were treated three times weekly with inhibitors at doses of 10 and 30 mg/kg or with saline control via oral gavage. Overall, we found that selective BTK inhibition was less effective than combined ITK/BTK or ITK inhibition in lengthening survival and reducing symptoms of cGVHD. ITK inhibition was most efficacious, with PCYC-274 and PCYC-401 demonstrating a nearly 50 percent reduction in GVHD scoring even at the 10 mg/kg dose, while 30 mg/kg of these compounds almost completely ameliorated GVHD symptomology. BTK/ITK and ITK-treated mice showed significant reductions in overall pathology. Significant reductions in dermal thickness and fibrosis were shown for all treatment groups. There was evidence of mixed Th1 and Th2 cytokine profiles in the skin of mice with dermal cGVHD, as both IFN-gamma and IL-4 were upregulated in the allogeneic control group, while kinase inhibition significantly reduced levels of these cytokines. Using an in vitro model of T-cell polarization, Th1 cell production of TNF-alpha and IFN-gamma were partially blocked by ITK. Th2 cell production of IL-4 was almost completely blocked synergistically by ITK and BTK inhibition. BTK-specific inhibition was unable to block either Th1 or Th2 cytokine production. Taken together, these results confirm previous reports that ITK-focused inhibition inhibits Th1 and Th2 cells. Additionally, the compound's effects on T-cell proliferation were tested by CFSE assay. Pure ITK inhibition was most effective at blocking T-cell proliferation, with no proliferation in PCYC-274-treated cells even at 0.1uM. PCYC-401 and PCYC-914 showed some inhibition at lower doses, with complete inhibition evident at 10uM. PCYC-804 was only partially able to block proliferation even at 10uM. In conclusion, we observed substantial benefit for differential inhibition of Tec kinases in GVHD, with ITK being most efficacious and Th1 cells being more resistant to inhibition, matching the previously reported findings of a Th2 to Th1 selective pressure in cells treated with ibrutinib. Our data warrants the further development of ITK and ITK/BTK inhibitors with specific inhibitory ratios to improve the treatment of GVHD and other T-cell mediated diseases.

353 Amlitelimab reduces serum IL-13 in a phase 2a clinical trial in atopic dermatitis without impacting T-cell expansion in a T-cell recall assay

Abstract Amlitelimab (SAR445229), a fully human non-depleting, non-cytotoxic, monoclonal antibody, binds to OX40Ligand (OX40L) on antigen-presenting cells (APC) to block OX40-OX40L interactions. In a 16-week, double-blind, Phase 2a trial (NCT03754309), amlitelimab induced clinically meaningful disease activity improvement in patients with moderate-to-severe atopic dermatitis (AD). To assess the effects of amlitelimab on interleukin (IL)-13 and T-cell recall responses. In the trial, 89 patients were randomized to amlitelimab low dose (LD; 200 mg loading/100 mg maintenance every 4 weeks [Q4W]), high dose (HD; 500 mg loading/250 mg maintenance Q4W), or placebo. Serum IL-13 levels were assessed by single molecule immunoassay (259 samples). Using human peripheral blood mononuclear cells from five healthy donors, a T-cell recall assay was performed. At baseline in the trial, IL-13 levels significantly correlated with disease severity (Eczema Area and Severity Index; r = 0.4784, P < 0.0001). Week 16 IL-13 levels were significantly reduced with amlitelimab vs. baseline but not placebo (median fold change [95% confidence interval, CI] from baseline to week 16 with P-values based on two-way Analysis of Variance [ANOVA] of log10-transformed fold change for patients with a complete dataset at week 16: LD 0.345 [0.23–0.44], P < 0.0001; HD 0.390 [0.30–0.63], P = 0.0002; placebo 0.835 [0.34–1.12], P = 0.1544). In a T-cell recall assay, amlitelimab significantly reduced IL-13 protein levels at days 3 and 6 without negatively impacting T-cell expansion, based on the percentage of proliferating CD4+ T-cells vs. isotype control. Amlitelimab decreased IL-13 levels in patients with AD and in a T-cell recall assay without negative effects on T-cell expansion, thus reducing inflammation without blocking T-cell proliferation during recall responses.

Glucocorticoid receptor modulates myeloid-derived suppressor cell function via mitochondria respiration and metabolism in immune thrombocytopenia

Abstract Methods We collected 27 immune thrombocytopenia (ITP) patients who had received high-dose dexamethasone treatment. The myeloid-derived suppressor cells (MDSCs) were induced in vitro and CHIP-qPCR assays were performed. Seahorse XF analyzer was used to analyze oxygen consumption rate and parameters of mitochondrial function of MDSCs. MDSCs were treated with CPT-1 inhibitor, etomoxir, to explore the effect of inhibiting fatty acid oxidation. Glucocorticoid receptor (GR) expression was blocked in murine MDSCs which were transplanted into ITP mice. Results The mRNA expression of GR and mtDNA-encoded genes (ATP8, COX1, CYTB, ND1, ND5), as well as the binding of GR to mtDNA in MDSCs were decreased in steroid-resistant ITP group compared to steroid-responsive ITP group and healthy controls. MDSCs in steroid-resistant patients had decreased levels of basal respiration, maximal respiration and ATP production, suggesting that the mitochondria of MDSCs in steroid-resistant group had lower activities of electron transport chains and oxidative phosphorylation. The function of MDSCs to inhibit T-cell proliferation was decreased in steroid-resistant group. Etomoxir reduced the ability of MDSCs to block T-cell proliferation in steroid-responsive group, but did not alter the suppressive function of MDSCs on T cells in steroid-resistant group. ITP mice transplanted with GR siRNA-treated MDSCs showed lower platelet counts than those with control siRNA-treated MDSCs, suggesting that the function of MDSCs to ameliorate ITP relied on GR. Conclusions This study demonstrated that GR-associated MDSCs impairments are involved in the pathogenesis of ITP. It might be related to the modulation of mitochondrial respiration and metabolism by GR.

A Multivalent ICAM-1 Binding Nanoparticle which Inhibits ICAM-1 and LFA-1 Interaction Represents a New Tool for the Investigation of Autoimmune-Mediated Dry Eye.

The autoimmune disorder, Sjögren’s syndrome (SS), is characterized by lymphocytic infiltration and loss of function of exocrine glands such as the lacrimal gland (LG) and salivary gland. SS-associated changes in the LG are associated with the development of autoimmune-mediated dry eye disease. We have previously reported the accumulation of intercellular adhesion molecule 1 (ICAM-1) in the LG of Non-Obese Diabetic (NOD) mice, a murine model of autoimmune-mediated dry eye in SS, in both LG acinar cells and infiltrating lymphocytes. ICAM-1 initiates T-cell activation and can trigger T-cell migration through binding to lymphocyte function-associated 1 antigen (LFA). To modulate this interaction, this study introduces a new tool, a multivalent biopolymeric nanoparticle assembled from a diblock elastin-like polypeptide (ELP) using the S48I48 (SI) ELP scaffold fused with a mouse ICAM-1 targeting peptide to form IBP-SI. IBP-SI forms a multivalent, monodisperse nanoparticle with a radius of 21.9 nm. Unlike the parent SI, IBP-SI binds mouse ICAM-1 and is internalized by endocytosis into transfected HeLa cells before it accumulates in lysosomes. In vitro assays measuring lymphocyte adhesion to Tumor Necrosis Factor TNF-α-treated bEnd.3 cells, which express high levels of ICAM-1, show that adhesion is inhibited by IBP-SI but not by SI, with IC50 values of 62.7 μM and 81.2 μM, respectively, in two different assay formats. IBP-SI, but not SI, also blocked T-cell proliferation in a mixed lymphocyte reaction by 74% relative to proliferation in an untreated mixed cell reaction. These data suggest that a biopolymeric nanoparticle with affinity for ICAM-1 can disrupt ICAM-1 and LFA interactions in vitro and may have further utility as an in vivo tool or potential therapeutic.

Tacrolimus Reverses UVB Irradiation-Induced Epidermal Langerhans Cell Reduction by Inhibiting TNF-α Secretion in Keratinocytes via Regulation of NF-κB/p65.

Background: Topical calcineurin inhibitors including tacrolimus and pimecrolimus are used in the treatment of many inflammatory skin diseases mainly via blocking T-cell proliferation. Our previous studies found that pimecrolimus 1% cream could reverse high-dose ultraviolet B (UVB) irradiation-induced epidermal Langerhans cell (LC) reduction via inhibition of LC migration. We conducted this study to investigate the effects of topical tacrolimus 0.03% ointment on high-dose UVB-irradiated human epidermal LCs.Methods: Twenty fresh human foreskin tissues were randomly divided into four groups as follows: Control, Tacrolimus (0.03%), UVB (180 mJ/cm2), and UVB (180 mJ/cm2) + Tacrolimus (0.03%). Four time points were set as follows: 0, 18, 24, and 48 h. We collected culture medium and tissues at each time point. The percentage of CD1a+ cells in the medium was detected by means of flow cytometry. Each tissue was prepared for immunohistochemistry, real-time quantitative PCR, and western blot. HaCaT cells were cultured and divided into four groups: Control, Tacrolimus (1 μg/ml), UVB (30 mJ/cm2), and UVB (30 mJ/cm2) + Tacrolimus (1 μg/ml). The cells were incubated for 24 h and prepared for real-time quantitative PCR and western blot.Results: Topical tacrolimus significantly reversed high-dose UVB irradiation-induced epidermal LC reduction and CD1a+ cell increment in culture medium. Tacrolimus significantly inhibited UVB irradiation-induced tumor necrosis factor-α (TNF-α) and nuclear factor kappa B (NF-κB)/p65 mRNA and protein expression in HaCaT cells. Tacrolimus also significantly inhibited high-dose UVB irradiation-induced TNF-α expression in cultured tissues. Finally, TNF-α antagonist (recombinant human TNF-α receptor II: IgG Fc fusion protein) could significantly reverse UVB irradiation-induced epidermal LC reduction.Conclusion: Topical tacrolimus 0.03% could reverse UVB irradiation-induced epidermal LC reduction by inhibiting TNF-α secretion in keratinocytes via regulation of NF-κB/p65.

Comparative effect of two pan-class I PI3K inhibitors used as anticancer drugs on human T cell function

The phosphatidylinositol 3-kinase (PI3K) pathway is commonly deregulated in cancer and, thus, PI3K has been recognized as an attractive molecular target for novel anti-cancer therapies. However, the effect of PI3K inhibitors on T-cell function, a key component of antitumor immunity, has been scantly explored. The objective of this study was to investigate the effect on human T-cell activation of two PI3K inhibitors currently being tested in clinical trials: PX-866 and BKM120. Their activity against a leukemic T cell line was also assessed. For that purpose, Jurkat cells or anti-CD3/anti-CD28 stimulated human peripheral blood mononuclear cells were cultured in the presence of different concentrations of PX-866 or BKM120 and their effect on T-cell proliferation, apoptosis, expression of activation markers and cytokine secretion was analyzed by flow cytometry. In addition, Akt and Erk phosphorylation was analyzed by Western blotting. Both PX-866 and BKM120 decreased viability of Jurkat cells and blocked cell cycle progression. Regarding primary T cells, both compounds similarly inhibited expression of activation markers and cytokine secretion, although they did not induce apoptosis of stimulated T cells. Interestingly, we found differences in their ability to block T-cell proliferation and IL-2 secretion, exerting BKM120 a more potent inhibition. These disparate effects could be related to differences observed in PI3K/Akt and RAS/MEK/ERK signaling between PX-866 and BKM120 treated cells. Our results suggest that, when selecting a PI3K inhibitor for cancer therapy, immunosuppressive characteristics should be taken into account in order to minimize detrimental effects on immune function.

The interaction between mesenchymal stem cells and steroids during inflammation.

Mesenchymal stem cells (MSCs) are believed to exert their regenerative effects through differentiation and modulation of inflammatory responses. However, the relationship between the severity of inflammation and stem cell-mediated tissue repair has not been formally investigated. In this study, we applied different concentrations of dexamethasone (Dex) to anti-CD3-activated splenocyte cultured with or without MSCs. As expected, Dex exhibited a classical dose-dependent inhibition of T-cell proliferation. Surprisingly, although MSCs also blocked T-cell proliferation, the presence of Dex unexpectedly showed a dose-dependent reversion of T-cell proliferation. This effect of Dex was found to be exerted through interfering STAT1 phosphorylation-prompted expression of inducible nitric oxide synthase (iNOS). Interestingly, inflammation-induced chemokines in MSCs was unaffected. To test the role of inflammation severity in stem cell-mediated tissue repair, we employed mice with carbon tetrachloride-induced advanced liver fibrosis and found that although MSCs alone were effective, concurrent administration of Dex abrogated the therapeutic effects of MSCs on fibrin deposition, serum levels of bilirubin, albumin, and aminotransferases, as well as T-lymphocyte infiltration, especially IFN-γ+CD4+ and IL-17A+CD4+T cells. Likewise, iNOS−/− MSCs, which produce chemokines but not nitric oxide under inflammatory conditions, are ineffective in treating advanced liver fibrosis. Therefore, inflammation has a critical role in MSC-mediated tissue repair. In addition, concomitant application of MSCs with steroids should be avoided.

Tumor microenvironment profoundly modifies functional status of macrophages: Peritoneal and tumor-associated macrophages are two very different subpopulations

Macrophages are key players in the inflammatory response. In this study, we tested the hypothesis that although all macrophage subpopulations in tumor hosts are affected by the disease, it is the close proximity to the tumor that induces major alterations in these cells. We compared tumor-associated macrophages (TAMs) with peritoneal macrophages from mice bearing D1-DMBA-3 mammary tumors (T-PEMs). Our results show that TAMs downregulate IL-12p70 but upregulate IL-12p40, IL-23, IL-6 and IL-10. Some NFκB and C/EBP transcription factors family members are decreased in TAMs; however NFκBp50 homodimers, STAT1/pSTAT1 and STAT3/pSTAT3 are overexpressed. Furthermore, while TAMs block T-cell proliferation and are more prone to apoptosis compared to T-PEMs, both types of macrophages have an impaired phagocytic capacity. Moreover, TAMs constitutively express iNOS and produce nitric oxide but do not express arginase and are Gr-1high and CD11blow. Collectively, our analysis of two spatially distinct macrophage subpopulations in tumor-bearing mice revealed that the tumor modulates them differently into two molecularly and functionally dissimilar macrophage subpopulations.

Abstract 398: Tumor microenvironment imposes major alterations and profoundly shapes functional status of macrophages: peritoneal and tumor-associated macrophages from tumor hosts are two very different subpopulations

Abstract Macrophages are key players in the inflammatory response and exhibit significant roles in the different stages of tumor progression. We have previously reported deficient functions of peritoneal macrophages of D1-DMBA3 mammary tumors bearers (T-PEMs). We showed that T-PEMs are impaired in inflammatory activity due to diminished expression of transcription factors NFκB and C/EBP. We have also demonstrated that T-PEMs display neither M1 nor M2 phenotypes, exhibit deficiencies in the production of several inflammatory cytokines, are less differentiated and show increased apoptosis. Importantly, we showed for the first time that their apoptosis in periphery contributes to increased myelopoiesis. We examined the blood monocytes from these tumor mice and demonstrated that these cells are neither inflammatory nor suppressive and are less differentiated, similar to the T-PEMs they later become. In the present study we investigate tumor-associated macrophages (TAMs) from the same tumor model and compare them with T-PEMs and with peritoneal macrophages from normal mice (N-PEMs). Our results show that TAMs downregulate IL-12p70, but upregulate IL-12p40, IL-23, IL-6 and IL-10 and chemokines and their receptors are very differently expressed in these two macrophages subpopulations. NFκB and C/EBP family members are decreased in TAMs as compared with T-PEMs, however NFκBp50 homodimers, STAT1/pSTAT1 and STAT3/pSTAT3 are all overexpressed. Moreover TAMs block T-cell proliferation and are more prone to apoptosis than T-PEMs due to a higher expression of activated caspase-3 and downregulation of Bcl-X. Our results show that T-PEMs and TAMs have equally impaired phagocytic capacity compared with fully-phagocytic N-PEMs. Moreover, TAMs constitutively express iNOS, produce nitric oxide but no arginase and are Gr-1high and CD11blow, thus are not classic myeloid-derived suppressor cells. Collectively, our results show that the exposure to different locations and tumor factor gradients determine macrophage phenotypes and functions. The tumor microenvironment, as the setting in most intimate contact with tumor cells is the one that most alters macrophage activity. Targeting tumor factors and other cells in the tumor microenvironment may allow reversion of macrophage dysfunction. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 398. doi:1538-7445.AM2012-398

Abstract 449: Tumor microenvironment induces profound immune suppression: Macrophages from peripheral and tumor locations differ in their degrees of inflammatory impairment

Abstract Macrophages are key players in the inflammatory response and exhibit significant roles in the different stages of tumor progression. We have previously reported the deficient functions of elicited macrophages recruited to the peritoneal cavity of mice bearing advanced D1-DMBA3 mammary tumors (T-PEMs). We showed that these T-PEMs are impaired in inflammatory activity due to diminished expression of transcription factors NFκB and C/EBP. We have also demonstrated that T-PEMs display neither M1 nor M2 phenotypes, exhibit deficiencies in the production of several inflammatory cytokines and proinflammatory signaling pathways intermediates and are less differentiated. Moreover, due in part to NFκB downregulation, increased apoptosis is observed in T-PEMs, a phenomenon which we reported for the first time that may contribute to increased myelopoiesis in tumor hosts. We have also recently examined the characteristics of blood monocytes from mice bearing the same mammary tumors and have demonstrated that these cells are neither inflammatory nor suppressive and are less differentiated, similar to the T-PEMs they later become. In the present study we investigate tumor-associated macrophages (TAMs) from the same animal tumor model and compare them with T-PEMs and with peritoneal macrophages from normal mice (N-PEMs). Our results show that TAMs downregulate IL-12p70, yet upregulate IL-12p40, IL-23 and IL-10. NFκB and C/EBP family members are decreased in TAMs as compared with T-PEMs, however NFκBp50 homodimers, STAT1/pSTAT1 and STAT3/pSTAT3 are all overexpressed. Interestingly, macrophages from tumor-bearing mice block T-cell proliferation, with TAMs exerting a more powerful inhibitory effect than T-PEMs. Also, TAMs are more prone to apoptosis than T-PEMs due to a higher expression of activated caspase 3 and downregulation of Bclx. TAMs also exhibit lower levels of differentiation than T-PEMs. In addition, our results show that T-PEMs and TAMs have equally impaired phagocytic capacity compared with fully-phagocytic N-PEMs. Moreover, TAMs constitutively express iNOS and produce nitric oxide as compared with T-PEMs, and they have constitutively lower arginase activity than T-PEMs. Furthermore, TAMs are Gr-1high and CD11blow, thus they are not classic myeloid-derived suppressor cells. Our results show that different locations in tumor hosts determine macrophage phenotypes and functions. The tumor microenvironment, as the location in most intimate contact with tumor cells, is the one that most alters macrophage activity. This is not only due to the occurrence of higher levels of tumor factors secreted by tumor cells, but also to the presence of other cell types that may interact with macrophages and modulate their activity. Targeting these tumor factors and cells in the tumor microenvironment will allow reversion of macrophage dysfunction. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 449. doi:10.1158/1538-7445.AM2011-449

Review of Symposium

Sirolimus (SRL) is a non-nephrotoxic immunosuppressive drug blocking T-cell proliferation through mTOR inhibition. SRL can be used as (1) an early drug in a calcineurin inhibitor-free protocol in the first 3 months after transplantation, (2) in the early and late conversion protocols as suggested by the multicenter randomized CONVERT trial, and (3) in recipients from marginal donors, because calcineurin inhibitors can increase the preexisting renal damage induced by age, hypertension, and diabetes that are frequent in elderly cadaveric donors. In any case, SRL should be used in patients with a cutoff of proteinuria (<or=800 mg/24 hr) or proteinuria-to-creatinine ratio less than 0.11.

FR255734, a Humanized, Fc-Silent, Anti-CD28 Antibody, Improves Psoriasis in the SCID Mouse-Psoriasis Xenograft Model

In psoriasis, CD28/B7 costimulatory molecules are well characterized. Here, using the severe combined immunodeficient (SCID) mouse-psoriasis xenograft model, we report therapeutic efficacy of a humanized anti-CD28 monoclonal antibody (FR255734; Astellas Pharmaceuticals Inc., Tokyo, Japan). Transplanted psoriasis plaques on the SCID mouse were treated weekly for 4 weeks with intraperitoneal injections of FR255734 at 10, 3, and 1-mg kg(-1) doses. Groups treated with doses of 10 and 3 mg kg(-1) had significant thinning of the epidermis and reduced HLA-DR-positive lymphocytic infiltrates. The length of the rete pegs changed from 415.2+/-59.6 to 231.4+/-40.4 microm (P<0.005) in the 10-mg kg(-1) group, and from 323.4+/-69.6 to 237.5+/-73.6 microm in the 3-mg kg(-1) group (P=0.002). Positive controls treated with CTLA4-Ig and cyclosporine had significant histological improvement, whereas plaques treated with saline and isotype controls (human and mouse IgG2) remained unchanged. In vitro studies have shown that FR255734 effectively blocked T-cell proliferation and proinflammatory cytokine production. These observations warrant studies to evaluate the efficacy of FR255734 in human autoimmune diseases.

Recurrent Headache as the Main Symptom of Acquired Cerebral Toxoplasmosis in Nonhuman Immunodeficiency Virus-infected Subjects With no Lymphadenopathy

Headache and/or migraine, a common problem in pediatrics and internal medicine, affect about 5% to 10% children and adolescents, and nearly 30% of middle-aged women. Headache is also one of the most common clinical manifestations of acquired Toxoplasma gondii infection of the central nervous system (CNS) in immunosuppressed subjects. We present 11 apparently nonhuman immunodeficiency virus-infected children aged 7 to 17 years (8 girls, 3 boys) and 1 adult woman with recurrent severe headaches in whom latent chronic CNS T. gondii infection not manifested by enlarged peripheral lymph nodes typical for toxoplasmosis, was found. In 7 patients, the mean serum IgG Toxoplasma antibodies concentration was 189 +/- 85 (SD) IU/mL (range 89 to 300 IU/mL), and in 5 other subjects, the indirect fluorescent antibody test titer ranged from 1:40 to 1:5120 IU/mL (n= <1:10 IU/mL). Some of the patients suffered also from atopic dermatitis (AD) and were exposed to cat and/or other pet allergens, associated with an increased IL-4 and decreased IFN-gamma production. These cytokine irregularities caused limited control of cerebral toxoplasmosis probably because IL-4 down-regulated both the production of IFN-gamma and its activity, and stimulated production of a low NO-producing population of monocytes, which allowed cysts rupture, increased parasite multiplication and finally reactivation of T. gondii infection. The immune studies performed in 4 subjects showed a decreased percentage of T lymphocytes, increased total number of lymphocytes B and serum IgM concentration, and impaired phagocytosis. In addition, few of them had also urinary tract diseases known to produce IL-6 that can mediate immunosuppressive functions, involving induction of the anti-inflammatory cytokine IL-10. These disturbances probably resulted from the host protective immune reactions associated with the chronic latent CNS T. gondii infection/inflammation. This is consistent with significantly lower enzyme indoleamine 2,3-dioxygenase (IDO) activity reported in atopic than in nonatopic individuals, and an important role that IDO and tryptophan degradation pathways plays in both, the host resistance to T. gondii infection and its reactivation. Analysis of literature information on the subjects with different types of headaches caused by foods, medications, and other substances, may suggest that their clinical symptoms and changes in laboratory data result at least in part from interference of these factors with dietary tryptophan biotransformation pathways. Several of these agents caused headache attacks through enhancing NO production via the conversion of arginine to citrulline and NO by the inducible nitric oxide synthase enzyme, which results in the high-output pathway of NO synthesis. This increased production of NO is, however, quickly down-regulated by NO itself because this biomolecule can directly inactivate NOS, may inhibit Ia expression on IFN-gamma-activated macrophages, which would limit antigen-presenting capability, and block T-cell proliferation, thus decreasing the antitoxoplasmatic activity. Moreover, NO inhibits IDO activity, thereby suppressing kynurenine formation, and at least one member of the kynurenine pathway, 3-hydroxyanthranilic acid, has been shown to inhibit NOS enzyme activity, the expression of NOS mRNA, and activation of the inflammatory transcription factor, nuclear factor-kB. In addition, the anti-inflammatory cytokines IL-4 and IL-10, TGF-beta, and a cytokine known as macrophage deactivating factor, have been shown to directly modulate NO production, sometimes expressing synergistic activity. On the other hand, IL-4 and TGF-beta can suppress IDO activity in some cells, for example human monocytes and fibroblasts, which is consistent with metabolic pathways controlled by IDO being a significant contributor to the proinflammatory system. Also, it seems that idiopathic intracranial hypertension, pseudotumor cerebri, and aseptic meningitis, induced by various factors, may result from their interference with IDO and inducible nitric oxide synthase activities, endogenous NO level, and cytokine irregularities which finally affect former T. gondii status 2mo in the brain. All these biochemical disturbances caused by the CNS T. gondii infection/inflammation may also be responsible for the relationship found between neurologic symptoms, such as headache, vertigo, and syncope observed in apparently immunocompetent children and adolescents, and physical and psychiatric symptoms in adulthood. We therefore believe that tests for T. gondii should be performed obligatorily in apparently immunocompetent patients with different types of headaches, even if they have no enlarged peripheral lymph nodes. This may help to avoid overlooking this treatable cause of the CNS disease, markedly reduce costs of hospitalization, diagnosis and treatment, and eventually prevent developing serious neurologic and psychiatric disorders.

Influence of Inflammatory Factors Produced during Graft-Versus-Host Disease on Immunological Properties of Mesenchymal Stem Cells (MSC).

MSC have been demonstrated to display non-HLA restricted immunosuppressive capacities in vitro and in vivo. Encouraging clinical results have been obtained using MSC infusion for the treatment of steroid-resistant acute graft-versus-host disease (aGVHD). However, very few data are available concerning the capacity of MSC to respond to inflammatory factors that are highly expressed during aGVHD or the influence of these factors on MSC outcome and immunological properties. In particular, the modulation, by environmental factors, of the production of the immunosuppressive enzyme indoleamine-2,3 dioxygenase (IDO) by MSC remains unexplored. The aim of our study was thus to evaluate the influence of the main inflammatory factors produced during GVHD on immunological properties of human clinical-grade MSC.We first confirmed that MSC expressed functional INFγR1 and TNFR1 since IFNγ and TNFα induced a broad set of genes, including those coding for the inflammatory chemokines CXCL9 and CXCL10. During GVHD, a disruption of gastro-intestinal tract integrity occurs and is associated with the release of various microbial compounds that are sensed by Toll Like Receptors (TLR). Using quantitative RT-PCR, we performed an exhaustive analysis of TLR expression on MSC. Whereas TLR2, TLR5, and TLR9 were essentially absent, TLR3 and TLR4, were highly expressed on human clinical-grade MSC. Accordingly, stimulation of MSC by poly(I:C) or LPS induced expression of CXCL9 and CXCL10. Lastly, we focused our work on CD40/CD40L interaction since a high proportion of CD4posT lymphocytes is activated during GVHD and expresses CD40L. We demonstrated that CD40 was present at the beginning of clinical-grade MSC culture and was significantly lost, both at RNA and protein level, after several cell passages. We also provided some evidence that CD40 was uniformly and highly expressed in vivo on CD45negCD14negCD73pos bone marrow cells that were previously shown to be highly enriched for MSC. Importantly, stimulation of MSC by trimeric CD40L was associated with a strong activation of NF-κB signalling pathway and the induction of IL8 gene expression.We then assessed the functional consequences of MSC stimulation by inflammatory factors on their immunological properties. IFNγ and TNFα, unlike TLR ligands and CD40L, induced the expression of relevant immunological markers such as HLA-I, HLA-II, CD54, CD106 and CD40. CD80 and CD86 were not inducible. Despite these phenotypic modifications, MSC did not become immunogenic and maintained their immunosuppressive properties. However, TNFα decreased and IFNγ increased this inhibitory effect. Interestingly, whereas IDO RNA was induced by TNFα and TLR ligands, IFNγ was the only inflammatory mediator able to induce IDO activity, as evaluated by HPLC. TNFα and LPS exerted a synergistic action with IFNγ for IDO activation.In conclusion, MSC express functional key receptors involved in inflammatory response. Their activation modulates properties of MSC into opposite ways: taking part of the inflammatory process through secretion of inflammatory chemokines, or blocking T-cell proliferation through induction of IDO. Such balance should be further studied to favour the development of new clinical trials involving MSC for treatment of aGVHD.

Resident microglia from adult mice are refractory to nitric oxide-inducing stimuli due to impaired NOS2 gene expression.

Microglia are the immunoregulatory cells of the central nervous system (CNS) and share many characteristics with resident macrophages in extracerebral tissues. Nitric oxide (NO) is secreted by macrophages following induction of the NO synthase gene NOS2 by stimuli elicited during a T-cell response and/or by microbial products. NO regulates both innate and adaptive immune responses, such as killing intracellular pathogens and inhibiting T-cell proliferation. Regulation of NO production by microglia, however, is poorly understood. We find that microglia from healthy adult mice produce negligible amounts of NO compared with resident macrophages during restimulation of peptide-specific CD8 T cells, and therefore cannot block T-cell proliferation. The impaired NO response extends to exogenous NOS2-inducing stimuli, including cytokines, CD40 ligation, and lipopolysaccharide. In contrast, microglia produce proinflammatory cytokines in response to these same stimuli, and therefore possess a relatively selective block in NO production. We go on to show that resident microglia fail to produce detectable levels of either the NOS2 enzyme or NOS2 RNA in response to NO-inducing stimuli. We therefore propose that microglia in the healthy adult brain exist in an "NO-incompetent" state in which NO production is blocked at the level of NOS2 RNA. The inability of resident microglia in the healthy CNS to produce NO may allow these immunoregulatory cells to modulate immune processes temporally, and may serve to protect the CNS from irreparable damage at the onset of infection or injury.

A neutralizing monoclonal antibody (mAb A24) directed against the transferrin receptor induces apoptosis of tumor T lymphocytes from ATL patients

AbstractAdult T-cell leukemia/lymphoma (ATL) is an aggressive lymphoid proliferative disease that exists under diverse clinical forms ranging from chronic to acute. Although leukemic cells from patients with ATL exhibit an intrinsic resistance to chemotherapy, monoclonal antibodies directed against CD25 (interleukin 2 receptor α [IL-2Rα] antibody) have been used as specific therapeutic agents. However, significant clinical results with these antibodies have been demonstrated only in chronic forms of ATL. In contrast to resting T cells, human T-cell lymphotropic virus type 1 (HTLV-1)–infected cells constitutively express high levels of surface transferrin receptor (TfR). Herein, we report the characterization of a new monoclonal antibody (mAb A24) directed against the human TfR and the evaluation of its capacity to block the proliferation of ATL cells ex vivo. We determined that A24 binds TfR with an equilibrium constant (K′d) of 2.7 nM and competes with transferrin for binding to TfR. A24 also inhibited [55Fe]-transferrin uptake in activated T cells and blocked T-cell proliferation. Moreover, A24 reduced and impaired TfR expression and recycling, respectively. Most important, we showed that A24 blocked the ex vivo proliferation of malignant T cells from both acute and chronic forms of ATL, through induction of programmed cell death. Therefore efficient therapeutic tools to treat acute forms of ATL might be derived from A24.

An overview of the actions of cyclosporine and FK506

Cyclosporine and FK506 are immunosuppressive drugs that have been extremely useful for treating graft-versus-host disease and autoimmune and inflammatory diseases, and they have truly revolutionized allograft transplantation. These drugs exert at least some of their immunosuppressive effects by blocking T-cell proliferation. Both drugs block T-cell proliferation by mechanisms that involve the inhibition of interleukin 2 production, a growth factor critical for T-cell proliferation. Recent studies, however, have shown that the effects of the drugs are not limited to blocking interleukin 2 production and that the production and the function of other molecules are also affected by these drugs. In this review, we examine recent studies on the molecular mechanisms of cyclosporine and FK506.

L-arginine metabolism in myeloid cells controls T-lymphocyte functions

Although current attention has focused on regulatory T lymphocytes as suppressors of autoimmune responses, powerful immunosuppression is also mediated by a subset of myeloid cells that enter the lymphoid organs and peripheral tissues during times of immune stress. If these myeloid suppressor cells (MSCs) receive signals from activated T lymphocytes in the lymphoid organs, they block T-cell proliferation. MSCs use two enzymes involved in arginine metabolism to control T-cell responses: inducible nitric oxide synthase (NOS2), which generates nitric oxide (NO) and arginase 1 (Arg1), which depletes the milieu of arginine. Th1 cytokines induce NOS2, whereas Th2 cytokines upregulate Arg1. Induction of either enzyme alone results in a reversible block in T-cell proliferation. When both enzymes are induced together, peroxynitrites, generated by NOS2 under conditions of limiting arginine, cause activated T lymphocytes to undergo apoptosis. Thus, NOS2 and Arg1 might act separately or synergistically in vivo to control specific types of T-cell responses, and selective antagonists of these enzymes might prove beneficial in fighting diseases in which T-cell responses are inappropriately suppressed. This Opinion is the second in a series on the regulation of the immune system by metabolic pathways.

Molecular actions of calcineurin inhibitors.

The immunosuppressive drugs cyclosporin A and FK-506, also called calcineurin inhibitors, have been useful for treating immune system-mediated diseases and have truly revolutionized allograft transplantation. Both drugs block T-cell proliferation by mechanisms that involve the inhibition of the key signaling phosphatase calcineurin, hence, the name calcineurin inhibitors. The inhibition of calcineurin activation by cyclosporin A and FK-506 blocks T-cell receptor-mediated production of interleukin-2 (IL-2), a growth factor critical for T-cell proliferation. Recent studies, however, suggest that the effects of the drugs are not limited to blocking calcineurin activation and IL-2 production. This review discusses the molecular actions of cyclosporin A and FK-506.