Impaired Interleukin-2 Research Articles

PGE2 inhibits TIL expansion by disrupting IL-2 signalling and mitochondrial function

Expansion of antigen-experienced CD8+ T cells is critical for the success of tumour-infiltrating lymphocyte (TIL)-adoptive cell therapy (ACT) in patients with cancer1. Interleukin-2 (IL-2) acts as a key regulator of CD8+ cytotoxic T lymphocyte functions by promoting expansion and cytotoxic capability2,3. Therefore, it is essential to comprehend mechanistic barriers to IL-2 sensing in the tumour microenvironment to implement strategies to reinvigorate IL-2 responsiveness and T cell antitumour responses. Here we report that prostaglandin E2 (PGE2), a known negative regulator of immune response in the tumour microenvironment4,5, is present at high concentrations in tumour tissue from patients and leads to impaired IL-2 sensing in human CD8+ TILs via the PGE2 receptors EP2 and EP4. Mechanistically, PGE2 inhibits IL-2 sensing in TILs by downregulating the IL-2Rγc chain, resulting in defective assembly of IL-2Rβ–IL2Rγc membrane dimers. This results in impaired IL-2–mTOR adaptation and PGC1α transcriptional repression, causing oxidative stress and ferroptotic cell death in tumour-reactive TILs. Inhibition of PGE2 signalling to EP2 and EP4 during TIL expansion for ACT resulted in increased IL-2 sensing, leading to enhanced proliferation of tumour-reactive TILs and enhanced tumour control once the cells were transferred in vivo. Our study reveals fundamental features that underlie impairment of human TILs mediated by PGE2 in the tumour microenvironment. These findings have therapeutic implications for cancer immunotherapy and cell therapy, and enable the development of targeted strategies to enhance IL-2 sensing and amplify the IL-2 response in TILs, thereby promoting the expansion of effector T cells with enhanced therapeutic potential.

NKTR-358: A novel regulatory T-cell stimulator that selectively stimulates expansion and suppressive function of regulatory T cells for the treatment of autoimmune and inflammatory diseases

Impaired interleukin-2 (IL-2) production and regulatory T-cell dysfunction have been implicated as immunological mechanisms central to the pathogenesis of multiple autoimmune and inflammatory diseases. NKTR-358, a novel regulatory T-cell stimulator, is an investigational therapeutic that selectively restores regulatory T-cell homeostasis in these diseases. We investigated NKTR-358's selectivity for regulatory T-cells, receptor-binding properties, ex vivo and in vivo pharmacodynamics, ability to suppress conventional T-cell proliferation in mice and non-human primates, and functional activity in a murine model of systemic lupus erythematosus. In vitro, NKTR-358 demonstrated decreased affinity for IL-2Rα, IL-2Rβ, and IL-2Rαβ compared with recombinant human IL-2 (rhIL-2). A single dose of NKTR-358 in cynomolgus monkeys produced a greater than 15-fold increase in regulatory T-cells, and the increase lasted until day 14, while daily rhIL-2 administration for 5 days only elicited a 3-fold increase, which lasted until day 7. Repeated dosing of NKTR-358 over 6 months in cynomolgus monkeys elicited cyclical, robust increases in regulatory T-cells with no loss in drug activity over the course of treatment. Regulatory T-cells isolated from NKTR-358-treated mice displayed a sustained, higher suppression of conventional T-cell proliferation than regulatory T-cells isolated from vehicle-treated mice. NKTR-358 treatment in a mouse model (MRL/MpJ-Faslpr) of systemic lupus erythematosus for 12 weeks maintained elevated regulatory T-cells for the treatment duration and ameliorated disease progression. Together, these results suggest that NKTR-358 has the ability to elicit sustained and preferential proliferation and activation of regulatory T-cells without corresponding effects on conventional T-cells, with improved pharmacokinetics compared with rhIL-2.

LRP8 activates STAT3 to induce PD-L1 expression in osteosarcoma.

Targeting programmed death-ligand 1 (PD-L1) may be an effective intervention for osteosarcoma and PD-L1 expression is controlled by diverse regulatory factors. Low-density lipoprotein receptor-related protein 8 (LRP8) regulates osteoblast differentiation and it is unclear whether and how LRP8 could contribute to osteosarcoma pathogenesis. In this study, we investigated the LRP8/signal transducer and activator of transcription 3 (STAT3)/PD-L1 network in osteosarcoma. The expression of LRP8, STAT3, and PD-L1 was measured in osteosarcoma tissues and paired normal tissues. The effects of LRP8 on STAT3 and PD-L1 expression were investigated in an osteosarcoma cell line. The effects on immunosuppression were investigated in an in vitro co-culture system with Jurkat cell line and osteosarcoma cell line. The effects of LRP8 were blocked by a LRP8 neutralizing antibody, dominant-negative STAT3, or STAT3 inhibitor. LRP8 was overexpressed in osteosarcoma compared to normal tissues and its level was correlated with phospho-STAT3 (p-STAT3) level in osteosarcoma tissues. In osteosarcoma cell lines, LRP8 increased p-STAT3 level and promoted nuclear translocation of STAT3. STAT3 activation also increased PD-L1 mRNA, protein, and promoter activity. In addition, LRP8 enhanced PD-L1 expression via STAT3. In a co-culture system, LRP8 overexpression in an osteosarcoma cell line impaired viability and interleukin-2 secretion of Jurkat cells and induced apoptosis of Jurkat cells. The effects of LRP8 could be blocked by neutralizing LRP8 antibody or STAT3 inhibitor. Blocking LRP8 inhibits proliferation and induces apoptosis of osteosarcoma cells. Our results provide evidence for a novel regulation network of LRP8/STAT3/PD-L1 in osteosarcoma and LRP8 may be a potential therapeutic target in osteosarcoma.

Interleukin-2 Deficiency Associated with Renal Impairment in Systemic Lupus Erythematosus.

Impaired interleukin-2 (IL-2) production was reported in systemic lupus erythematosus (SLE). The aim of this study was to investigate the clinical relevance of serum IL-2 and therapeutic effects of recombinant IL-2 (rIL-2) in SLE, especially in lupus nephritis (LN). Decreased serum IL-2 was found in patients with active LN (P = 0.014) and correlated with 24-h urine protein excretion (r = -0.281, P = 0.026). Compared with LN patients with decreased levels of serum IL-2, patients with increased levels had better remission rate (P = 0.041). Furthermore, patients with exogenous low-dose IL-2 supplement demonstrated better improved nephritis and higher remission rate (55.56%, P = 0.058) than those with conventional therapy. In addition, the percentages of regulator T (Treg) cells expanded in LN patients with low-dose recombinant human IL-2 treatment (P = 0.007), especially in LN patients achieving remission (P = 0.010). IL-2 deficiency is associated with renal impairment that can be improved by exogenous IL-2 supplement.

Low-Dose IL-2 Signaling Is Specifically Impaired in Regulatory T Cells from T1D Patients

Background: The response to interleukin-2 (IL-2) is essential for the stability and function of regulatory T cells (Tregs) in vivo. Impaired IL-2 receptor signaling might play a crucial role in the decreased function of Tregs in autoimmunity but might also contribute to the increased suppressive capacity of Tregs in cancer. In this study we aimed to examine differences in the phosphorylation of STAT5 as a downstream measure of IL-2 signaling in type 1 diabetes (T1D), rheumatoid arthritis (RA), colo-rectal cancer (CRC) and healthy controls. Material and Methods: Phosphorylation of STAT5 was quantified in 10 T1D, 10 RA, 10 CRC and 10 healthy control samples. Freshly drawn whole blood was stimulated with increasing amounts of IL-2 [0, 0.5, 1, 5, 10 U/ml] for 30 minutes. The expression of phosphorylated STAT5 (pSTAT5) in Tregs was quantified by flow cytometry. Results: Tregs from T1D patients showed significantly decreased levels of pSTAT5 when compared to healthy controls after stimulation with 0.5 U IL-2 (mean fluorescence intensity, MFI: 896 ± 502 vs. 3435 ± 1035, p<0.001) and after stimulation with 1 U IL-2/ml (MFI: 1095 ± 942 vs. 3835 ± 1415, p=0.004). Tregs from RA patients showed decreased levels after stimulation with 0.5 U IL-2/ml (p=0.043) but not after stimulation with 1U IL-2/ml when compared to healthy controls. No significant differences between cells from CRC patients and controls were found. Stimulation with 5 or 10 U IL-2/ml led to comparable levels of pSTAT5 in all investigated samples. Conclusion: The response towards low doses of IL-2 is significantly decreased in Tregs from T1D and RA patients. This might contribute to the loss of tolerance and increased autoimmunity in those diseases. However, low dose IL2 signaling does not seem to be involved in the increased suppressive capacity of Tregs in CRC patients. Disclosure B. Prietl: None. S. Kofler: None. S. Stanzer: None. B.M. Obermayer-Pietsch: None. T.R. Pieber: Consultant; Self; Arecor, AstraZeneca, Eli Lilly and Company, Novo Nordisk A/S, Sanofi. Employee; Self; CBmed. Research Support; Self; Novo Nordisk A/S, AstraZeneca. H. Sourij: Speaker's Bureau; Self; Boehringer Ingelheim GmbH, Novo Nordisk A/S, Amgen Inc., Sanofi, MSD K.K.. Research Support; Self; AstraZeneca, Boehringer Ingelheim GmbH, MSD K.K., GI Dynamics Inc..

Pre-diagnostic genotyping identifies T1D subjects with impaired Treg IL-2 signaling and an elevated proportion of FOXP3+IL-17+ cells.

T-regulatory cells (Tregs) are essential for immune tolerance, and animal studies implicate their dysfunction in type 1 diabetes (T1D) pathogenesis. Tregs require interleukin-2 (IL-2) for their suppressive function, and variants in IL-2/IL-2R pathway genes have been associated with T1D. We previously reported that recent-onset T1D subjects have an increased population of FOXP3lo Tregs that secrete the pro-inflammatory cytokine, interleukin-17 (IL-17). We hypothesize that IL-2 signaling defects may drive T1D development by skewing protective Tregs towards an inflammatory Th17 phenotype. Overall, we found that the proportion of FOXP3+IL-17+ cells in T1D subjects pre-diagnosis was unchanged compared with healthy controls. However, stratification by IL2RA single-nucleotide polymorphisms revealed that T1D subjects with the rs3118470 CC risk variant have Tregs with IL-2 signaling defects and an increased proportion of FOXP3+IL-17+ cells before diagnosis. These data suggest a potential mechanism for genetically controlled loss of Treg function via dysfunctional IL-2 signaling in T1D.

Altered Maturation Status and Possible Immune Exhaustion of CD8 T Lymphocytes in the Peripheral Blood of Patients Presenting With Acute Coronary Syndromes.

Inflammation in response to oxidized lipoproteins is thought to play a key role in acute coronary syndromes (ACS), but the pattern of immune activation has not been fully characterized. We sought to perform detailed phenotypic and functional analysis of CD8 T lymphocytes from patients presenting with ACS to determine activation patterns and potential immunologic correlates of ACS. We used polychromatic flow cytometry to analyze the cytokine production profiles of naïve, effector, and memory CD8 T cells in patients with ACS compared with control subjects with stable coronary artery disease. ACS was associated with an altered distribution of circulating CD8(+) T-cell maturation subsets with reduced proportions of naïve cells and expansion of effector memory cells. ACS was also accompanied by impaired interleukin-2 production by phenotypically naïve CD8 T cells. These results were validated in a second replication cohort. Naïve CD8 cells from patients with ACS also had increased expression of programmed cell death-1, which correlated with interleukin-2 hypoproduction. In vitro, stimulation of CD8 T cells with oxidized low-density lipoprotein was sufficient to cause programmed cell death-1 upregulation and diminished interleukin-2 production by naïve CD8 T cells. In this exploratory analysis, naïve CD8(+) T cells from patients with ACS show phenotypic and functional characteristics of immune exhaustion: impaired interleukin-2 production and programmed cell death-1 upregulation. Exposure to oxidized low-density lipoprotein recapitulates these features in vitro. These data provide evidence that oxidized low-density lipoprotein could play a role in immune exhaustion, and this immunophenotype may be a biomarker for ACS.

HIV mono-infection is associated with an impaired anti-hepatitis C virus activity of natural killer cells.

Hepatitis C virus (HCV) infection in HIV(+) patients is associated with faster liver disease progression compared with HCV mono-infection. HIV-associated immune defects are considered to play an important role in this context. Here, we analyzed the effects of HIV infection on natural killer (NK)-cell-mediated anti-HCV activity. NK cell phenotype and interferon gamma (IFN-γ) production, NK cell-mediated inhibition of HCV replication and CD4 T-cell/NK cell interactions were studied in treatment naive HIV (n = 22), and HIV patients under combined antiretroviral therapy (n = 29), compared with healthy controls (n = 20). NK cell-mediated inhibition of HCV replication was analyzed using the HuH7A2HCVreplicon model. IFN-γ production of NK cells as well as interleukin-2 secretion of CD4 T lymphocytes were studied by flow cytometry. Peripheral blood mononuclear cells from HIV(+) patients displayed a significantly impaired anti-HCV activity, irrespective of combined antiretroviral therapy. This could in part be explained by HIV-associated decline in NK cell numbers. In addition, NK cell IFN-γ production was significantly impaired in HIV infection. Accordingly, we found low frequency of IFN-γ(+) NK cells in HIV(+) patients to be associated with ineffective inhibition of HCV replication. Finally, we show that CD4 T-cell-mediated stimulation of NK cell IFN-γ production was dysregulated in HIV infection with an impaired interleukin-2 response of NK cells. HIV infection has a strong suppressive effect on anti-HCV activity of NK cells. This may contribute to low spontaneous clearance rate and accelerated progression of HCV-associated liver disease observed in HIV(+) patients.

A variable degree of autoimmunity in the pedigree of a patient with type 1 diabetes homozygous for thePTPN22 1858T variant

We investigated whether the PTPN22 C1858T polymorphism is associated with the autoimmune conditions present in the family of a child affected by type 1 diabetes (T1D) carrying the TT genotype (index patient) and the potential immunological effect of the variant. We found that nine family members carried the CT genotype and five suffered from autoimmunity. Interestingly, anti-ZnT8 antibodies were detected in T1D patients and in three healthy relatives. In the TT patient, we showed diminished T-cell proliferation and reduced interleukin-2 (IL-2) and interferon-gamma (IFN-γ) production. A marked reduction of IL-2 was also observed for all CT relatives with autoimmunity and a lack of IFN-γ production was observed for the younger brother of the index patient, heterozygous for the polymorphism. In this family, the C1858T variant might confer a high risk of autoimmunity. Moreover, our data confirm that impaired IL-2 production upon T-cell receptor stimulation is associated with autoimmunity in the carriers of the polymorphism. This study might prompt to extend the panel of risk markers in relatives of subjects affected by T1D.

MTOC translocation modulates IS formation and controls sustained T cell signaling

The translocation of the microtubule-organizing center (MTOC) toward the nascent immune synapse (IS) is an early step in lymphocyte activation initiated by T cell receptor (TCR) signaling. The molecular mechanisms that control the physical movement of the lymphocyte MTOC remain largely unknown. We have studied the role of the dynein–dynactin complex, a microtubule-based molecular motor, in the process of T cell activation during T cell antigen–presenting cell cognate immune interactions. Impairment of dynein–dynactin complex activity, either by overexpressing the p50-dynamitin component of dynactin to disrupt the complex or by knocking down dynein heavy chain expression to prevent its formation, inhibited MTOC translocation after TCR antigen priming. This resulted in a strong reduction in the phosphorylation of molecules such as ζ chain–associated protein kinase 70 (ZAP70), linker of activated T cells (LAT), and Vav1; prevented the supply of molecules to the IS from intracellular pools, resulting in a disorganized and dysfunctional IS architecture; and impaired interleukin-2 production. Together, these data reveal MTOC translocation as an important mechanism underlying IS formation and sustained T cell signaling.

Mechanism of a lymphocyte abnormality associated with HLA-B8/DR3: role of interleukin-1

Lymphocytes from normal individuals with the histocompatibility antigens HLA-B8 and DR3 have impaired proliferative responses when stimulated with suboptimal concentrations of mitogens. We have previously shown that an important factor in the impaired response is a failure to produce normal quantities of interleukin-2 (IL-2). To examine the mechanism of decreased responsiveness further, we measured interleukin-1 (IL-1) production of low responder subjects compared with controls. The peripheral blood mononuclear cells of five low responder individuals with HLA-B8/DR3 stimulated with 0.05 micrograms/ml of phytohaemagglutinin (PHA) accumulated only 0.036 U/ml of IL-1 compared with 0.32 U/ml for normal responders. There was a highly significant correlation between the PHA-stimulated IL-1 concentration at 12 h and the subsequent IL-2 concentration at 48 h(r = 0.89, P less than 0.0001) suggesting a role of decreased IL-1 production in the impaired response. A study of unfractionated or column-fractionated culture supernatants revealed no evidence that the decreased IL-1 activity in the supernatants of low responder subjects was related to increased IL-1 inhibitor concentrations. These results suggest that impaired IL-2 production and lymphocyte proliferation in healthy subjects with HLA-B8/DR3 may be mediated at least in part by decreased IL-1 production, and implicates a defect of a very early event in lymphocyte activation.

Impaired Interleukin-2 Synthesis and T Cell Proliferation Following Antibody-mediated CD3 and CD2 or CD28 Cross-linking in Trans: Evidence that T Cell Activation Requires the Engagement of Costimulatory Molecules Within the Immunological Synapse

Although the T cell costimulatory molecules CD2 and CD28 are enriched within the immunological synapse (IS), it has been suggested that costimulatory molecules need not be localized to the contact site between a T cell and an antigen-presenting cell (APC) in order to costimulate T cell activation. To determine whether CD2 or CD28 engagement outside of the IS is sufficient to costimulate T cell activation, we compared mouse T cell responses to anti-CD3 and anti-CD2 monoclonal antibodies (mAbs) or anti-CD3 and anti-CD28 mAbs immobilized on the same, i.e., in cis, or on different, i.e., in trans, 10 micron polystyrene microspheres. In comparison to T cells that were stimulated with co-immobilized anti-CD3 and anti-CD2 or anti-CD28 mAbs, DNA synthesis, interleukin (IL)-2 production, and cellular proliferation were all severely impaired following T cell stimulation with anti-CD3 and anti-CD2 mAbs or anti-CD3 and anti-CD28 mAbs on different microspheres. Deficient cellular proliferation and IL-2 synthesis by T cells that experienced CD3 and CD2 or CD28 cross-linking in trans provides evidence that costimulatory molecules must function in the context of the IS for optimal T cell activation.

Inhibition of (S)-armepavine from Nelumbo nucifera on autoimmune disease of MRL/MpJ- lpr/lpr mice

T cell immune responses play important roles in the pathogenesis of systemic lupus erythematosus (SLE). (S)-Armepavine (C 19H 23O 3N; MW313) from Nelumbo nucifera suppresses T cells proliferation. To study its potential benefit on SLE, we examined effects of (S)-armepavine on MRL/MpJ- lpr/lpr mice, which have similar disease features to human SLE. MRL/MpJ- lpr/lpr mice were treated orally with (S)-armepavine for 6 weeks and their SLE characteristics were evaluated. The results revealed that (S)-armepavine prevented lymphadenopathy and elongated life span of MRL/MpJ- lpr/lpr mice. It seemed to be mediated by inhibition of splenocytes proliferation, suppression of interleukin-2 (IL-2), interleukin-4, interleukin-10, and interferon-γ (IFN-γ) gene expressions, reduction of glomerular hypercellularity and immune complexes deposition, and decrease of urinary protein and anti-double stranded DNA autoantibody production. Furthermore, the data demonstrated (S)-armepavine impaired IL-2 and IFN-γ transcripts in human peripheral blood mononuclear cells. We suggest that (S)-armepavine may be an immunomodulator for the management of autoimmune diseases like SLE.

A Secreted Low--Molecular-Weight Protein From Helicobacter pylori Induces Cell-Cycle Arrest of T Cells

Although Helicobacter pylori is recognized by the human immune system, the bacteria are not eliminated and lead to a chronic inflammation of the gastric mucosa. We investigated the interaction of H. pylori with human lymphocytes. T and B lymphocytes were isolated from H. pylori-infected patients and stimulated with anti-CD3/CD28 or interleukin-6. Proliferation of lymphocytes was abolished on co-incubation with different H. pylori strains (1-5 bacteria/cell) or with protein extracts of culture supernatants. Inhibition of proliferation was independent of known virulence factors. The factor is a protein or protein complex with an apparent molecular weight between 30 and 60 kilodaltons, clearly distinct from VacA. Although antigen-specific activation of T cells (as shown by nuclear factor of activated T cells [NFAT]-activation, interferon-gamma production, and CD25 or CD69 up-regulation) remained intact, cell-cycle analysis showed that S-phase entry of T cells was inhibited completely by H. pylori. Consequently, stimulated T cells arrested in the G1 phase of the cell cycle. Western blot analysis showed markedly reduced phosphorylation of the retinoblastoma protein (pRb), suggesting inhibition of G1 cyclin-dependent kinase activity. In line with this, activities of cyclin D3 and cyclin E were down-regulated, and levels of the cyclin-dependent kinase inhibitor p27Kip1 were increased. Mouse embryonic fibroblasts deficient in p27 showed a decrease in H. pylori-induced inhibition of cell proliferation, suggesting a central role for p27 in mediating H. pylori-induced G1 arrest. Induction of cell-cycle arrest in lymphocytes may be of major significance for the chronic persistence of bacteria in the human stomach.

A Novel ERK-dependent Signaling Process That Regulates Interleukin-2 Expression in a Late Phase of T Cell Activation

Engagement of the T cell antigen receptor (TCR) rapidly induces multiple signal transduction pathways, including ERK activation. Here, we report a critical role for ERK at a late stage of T cell activation. Inhibition of the ERK pathway 2-6 h after the start of TCR stimulation significantly impaired interleukin-2 (IL-2) production, whereas the same treatment during the first 2 h had no effect. ERK inhibition significantly impaired nuclear translocation of c-Rel with a minimum reduction of NF-AT activity. Requirement for sustained ERK activation was also confirmed using primary T cells. To induce sustained activation of ERK, T cells required continuous engagement of TCR. Stimulation of T cells with soluble anti-TCR antibody resulted in activation of ERK lasting for 60 min, but failed to induce IL-2 production. In contrast, plate-bound anti-TCR antibody activated ERK over 4 h and induced IL-2. Furthermore, T cells treated with soluble anti-TCR antibody produced IL-2 when phorbol 12-myristate 13-acetate, which activates ERK, was present in the culture medium 2-6 h after the start of stimulation. Together, the data demonstrate the presence of a novel activation process following TCR stimulation that requires ERK-dependent regulation of c-Rel, a member of the NF-kappaB family.

P59 fyn is upregulated in anergic CD8 + T cells

The ultimate goal in clinical transplantation is achievement of graft tolerance. Despite long-term immunosuppression, alloantigens on transplants elicit alloresponses that can initiate organ rejection. Acute rejection is mediated by CD8 + cytotoxic T cells, whereas chronic rejection is a result of many factors including non-immunological events. The aim of this study was to examine the molecular requirements of T cell anergy, a cellular state that is an integral component of tolerance in vivo. In vitro, the tolerant state is usually best represented by T cell anergy, which is defined by loss of the ability of T cells to produce and secrete interleukin-2 upon restimulation. In the literature, molecular changes in anergic CD4 + T cells have been studied in great detail, but only little is known about functional and biochemical characteristics of anergic CD8 + T lymphocytes. In this study, we demonstrate, that CD8 + T cells are rendered anergic by TCR stimulation without costimulation. They exhibit impaired interleukin-2 production and tyrosine-phosphorylation, but markedly upregulated p59 fyn expression, which could be shown to be an early event during anergization. Anergic CD8 + T lymphocytes show elevated surface expression of early activation markers as well as costimulatory molecules, especially that of CTLA4. These results, are an important component for the discovery of potential molecular targets, which contribute to the development and maintenance of tolerance.

Relationships between immunity and dietary and serum antioxidants, trace metals, B vitamins, and homocysteine in elderly men and women

It is well known that nutritional status has profound effects on immunity. The compromised cellular immunity that occurs in many otherwise healthy older people includes impaired interleukin-2 (IL-2) production and anergy to skin test antigens. The latter has been associated prospectively with increased mortality in the elderly. We studied dietary and blood concentrations of vitamins A, B6, C and E, folate, β carotene, and zinc and their relationship to delayed hypersensitivity skin test responses (DHST) and serum soluble IL-2 receptor concentrations (IL-2R) in 65 healthy independently-living men and women aged 69.8 ± 7.2 years. Serum concentrations of vitamin B12 and copper and dietary lycopene were also measured. Excluded were subjects who had used vitamin or mineral supplements in the preceding 3 months, since supplementation may improve DHST responses. IL-2R concentrations were positively (p < 0.05) associated with serum concentrations of homocysteine, vitamin B6 and BMI, and negatively associated with serum β-carotene and dietary lycopene. In a multiple regression model, these 5 variables explained 52% of the variability in IL-2R. The percentage of subjects with anergy to a panel of 7 skin test antigens was 25%. DHST responses were negatively associated with T helper cell numbers and serum retinol, T helper cell numbers were positively associated with serum copper, and natural killer cell numbers were positively associated with dietary folate and vitamin B6. Serum homocysteine concentrations were negatively associated with plasma concentrations of folate, and vitamin B12, as well as positively with serum IL-2R. In a multiple regression model, these 3 concentrations explained 27% of the variability in serum homocysteine. The results suggest that IL-2 metabolism may be influenced by several dietary antioxidants and B vitamins including those that alter homocysteine concentrations.

Downregulation of JAK3 Protein Levels in T Lymphocytes by Prostaglandin E2 and Other Cyclic Adenosine Monophosphate-Elevating Agents: Impact on Interleukin-2 Receptor Signaling Pathway

The Janus kinase, JAK3 plays an important role in interleukin-2 (IL-2)-dependent signal transduction and proliferation of T lymphocytes. Our findings show that prostaglandin E2 (PGE2) can inhibit upregulation of JAK3 protein in naive T cells and can downregulate its expression in primed cells. Reduction in JAK3 was selective because expression of other tyrosine kinases (JAK1, p56(lck), and p59(fyn)) and signal transducer and activator of transcription (STAT)5, which are linked to IL-2 receptor (IL-2R) signaling pathway, were not affected. Inhibition of JAK3 may be controlled by intracellular cyclic adenosine monophosphate (cAMP) levels, as forskolin, a direct activator of adenylate cyclase and dibutyryl cAMP (dbcAMP), a membrane permeable analogue of cAMP suppressed JAK3 expression. Moreover, 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of cAMP phosphodiesterase, potentiated PGE2-induced suppression of JAK3. In naive T cells, but not primed T cells, PGE2 and other cAMP elevating agents also caused a modest reduction in surface expression of the common gamma chain (gammac) that associates with JAK3. The absence of JAK3, but not IL-2R in T cells correlated with impaired IL-2-dependent signal transduction and proliferation. The alteration in IL-2 signaling included decreased tyrosine phosphorylation and DNA binding activity of STAT5 and poor induction of the c-Myc and c-Jun pathways. In contrast, IL-2-dependent induction of Bcl-2 was unaffected. These findings suggest that suppression of JAK3 levels may represent one mechanism by which PGE2 and other cAMP elevating agents can inhibit T-cell proliferation.

Downregulation of JAK3 Protein Levels in T Lymphocytes by Prostaglandin E2 and Other Cyclic Adenosine Monophosphate-Elevating Agents: Impact on Interleukin-2 Receptor Signaling Pathway

AbstractThe Janus kinase, JAK3 plays an important role in interleukin-2 (IL-2)–dependent signal transduction and proliferation of T lymphocytes. Our findings show that prostaglandin E2(PGE2) can inhibit upregulation of JAK3 protein in naive T cells and can downregulate its expression in primed cells. Reduction in JAK3 was selective because expression of other tyrosine kinases (JAK1, p56lck, and p59fyn) and signal transducer and activator of transcription (STAT)5, which are linked to IL-2 receptor (IL-2R) signaling pathway, were not affected. Inhibition of JAK3 may be controlled by intracellular cyclic adenosine monophosphate (cAMP) levels, as forskolin, a direct activator of adenylate cyclase and dibutyryl cAMP (dbcAMP), a membrane permeable analogue of cAMP suppressed JAK3 expression. Moreover, 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of cAMP phosphodiesterase, potentiated PGE2-induced suppression of JAK3. In naive T cells, but not primed T cells, PGE2 and other cAMP elevating agents also caused a modest reduction in surface expression of the common gamma chain (γc) that associates with JAK3. The absence of JAK3, but not IL-2R in T cells correlated with impaired IL-2–dependent signal transduction and proliferation. The alteration in IL-2 signaling included decreased tyrosine phosphorylation and DNA binding activity of STAT5 and poor induction of the c-Myc and c-Jun pathways. In contrast, IL-2–dependent induction of Bcl-2 was unaffected. These findings suggest that suppression of JAK3 levels may represent one mechanism by which PGE2 and other cAMP elevating agents can inhibit T-cell proliferation.

Influence of antigen dose and costimulation on the primary response of CD8+ T cells in vitro.

The influence of costimulation on the primary response of CD8+ T cells to class I alloantigens was studied with the aid of a T cell receptor transgenic model and defined peptides as antigen. With small doses of antigen, the proliferative response of CD8+ cells was high early in culture but was of brief duration and declined to low levels by day 4; this abbreviated response was associated with limited production of interleukin 2 (IL-2) and was strongly dependent upon costimulation via CD8-major histocompatibility complex class I and CD28-B7 interactions. The response to large doses of antigen was quite different in two respects. First, large doses of antigen inhibited the early (day 3) proliferative response but caused a marked elevation of the response late in culture (day 5); these altered kinetics were associated with increased production of IL-2. Second, the initial proliferative response to large doses of antigen did not require costimulation: indeed, blocking costimulation with CTLA4lg or anti-CD8 monoclonal antibody enhanced the early proliferative response. However, blocking costimulation impaired IL-2 production and prevented the late proliferative response. These findings indicate that the requirement for costimulation of T cells can be partly overcome by increasing the dose of antigen to a high level. However, costimulation plays a key role in prolonging the response, presumably by triggering strong and sustained production of IL-2.