Major T-cell Subsets Research Articles

Abstract B32: Lymphocytes and immune checkpoint biomarker expression in sarcomas

Abstract Recent clinical trials of immune checkpoint inhibitors have raised hopes for sarcoma therapy, but they have not taken into account the variability of the immune microenvironment in their design or interpretation. Here, we present a comprehensive analysis of tumor-infiltrating lymphocytes (TILs) across a spectrum of sarcoma types, in order to better identify sarcoma populations that are more likely to respond to specific immunotherapies. Methods: From a tissue microarray database of 1918 formalin-fixed, paraffin-embedded sarcoma tissue samples spanning 24 subtypes, immunohistochemistry was performed to quantify TILs, to characterize major T-cell subsets (CD4, CD8, FOXP3), and to evaluate expression of targetable immune checkpoint ligand PDL1 (programmed death ligand 1) and its immune cell receptor PD1. PDL1 was scored by percentage of tumor cells exhibiting positive membranous staining; all other markers were quantified by counting positive-staining lymphocytes. Results: Lymphocytes were present in 93% of samples (ranging from 1-1300 TILS/mm2), of which 63% were CD8+. Dedifferentiated liposarcoma (DDLPS) showed the greatest enrichment, with a median count of 103 TILs/mm2. Other subtypes with notably high TIL counts include undifferentiated pleomorphic sarcoma (UPS; 38 TILs/mm2), myxofibrosarcoma (35 TILs/mm2), well-differentiated liposarcoma (26 TILs/mm2), osteosarcoma (21 TILs/mm2), and leiomyosarcoma (19 TILs/mm2). Without exception, translocation-associated sarcoma subtypes had very low levels of infiltrating lymphocytes (median 9 TILs/mm2). The subtype with the lowest levels of TILs was chondrosarcoma (0 TILs/mm2). PDL1 was present (≥1% tumor cell staining cutpoint) in 7% of samples, and stained ≥10% of tumor cells in 5.3% of samples. The subtypes that account for the majority of this PDL1 positivity are UPS (15/72), osteosarcoma (12/224), malignant peripheral nerve sheath tumor (9/74), myxofibrosarcoma (8/52), and DDLPS (6/60). Angiosarcoma had the highest proportion of positive cases (60%), but this was based on a small number of samples (n=5). PD1 lymphocyte staining was also low overall, with 14% of samples having at least one PD1+ TIL per mm2. The subtypes with the highest proportions of PD1+ cases were DDLPS (36/79), UPS (23/80), leiomyosarcoma (8/19), and epithelioid sarcoma (4/8). Conclusions: Lymphocyte infiltration is predominantly limited to complex karyotype sarcomas and is rarely seen in translocation-associated sarcomas. The very highest levels of infiltrates are observed in DDLPS and the very lowest in chondrosarcoma. CD8+ effector T cells are the predominant lymphocyte subset present in sarcomas. PDL1 and PD1 expression are low overall for sarcomas, but some subtypes (UPS, DDLPS) appear to employ PDL1 immune blockade in up to 20% of cases. Further studies are pending to determine the significance of these findings for immunotherapy response. Citation Format: Amanda R. Dancsok, David Thomas, Jean-Yves Blay, Robert G. Maki, Torsten O. Nielsen, Elizabeth G. Demicco. Lymphocytes and immune checkpoint biomarker expression in sarcomas [abstract]. In: Proceedings of the AACR Conference on Advances in Sarcomas: From Basic Science to Clinical Translation; May 16-19, 2017; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(2_Suppl):Abstract nr B32.

The role of ADAM17 in the T-cell response against bacterial pathogens.

ADAM17 is a member of the A Disintegrin And Metalloproteinase family of proteases. It is ubiquitously expressed and causes the shedding of a broad spectrum of surface proteins such as adhesion molecules, cytokines and cytokine receptors. By controlled shedding of these proteins from leukocytes, ADAM17 is able to regulate immune responses. Several ADAM17 targets on T cells have been implicated in T-cell migration, differentiation and effector functions. However, the role of ADAM17 in T-cell responses is still unclear. To characterize the function of ADAM17 in T cells, we used Adam17fl/fl×CD4cre+ mice with a T-cell restricted inactivation of the Adam17 gene. Upon stimulation, ADAM17-deficient CD4+ and CD8+ T cells were impaired in shedding of CD62L, IL-6Rα, TNF-α, TNFRI and TNFRII. Surprisingly, we could not detect profound changes in the composition of major T-cell subsets in Adam17fl/fl×CD4cre+ mice. Following infection with Listeria monocytogenes, Adam17fl/fl×CD4cre+ mice mounted regular listeria-specific CD4+ TH1 and CD8+ T-cell responses and were able to control primary and secondary infections. In conclusion, our study indicates that ADAM17 is either not required in T cells under homoeostatic conditions and for control of listeria infection or can be effectively compensated by other mechanisms.

Tbet is a critical modulator of FoxP3 expression in autoimmune graft-versus-host disease.

CD4+ T-helper subsets drive autoimmune chronic graft-versus-host disease, a major complication after allogeneic bone marrow transplantation. However, it remains unclear how specific T-helper subsets contribute to chronic graft-versus-host disease. T-helper type 1 cells are one of the major disease-mediating T-cell subsets and require interferon-γ signaling and Tbet expression for their function. Regulatory T cells on the other hand can inhibit T-helper type 1 cell-mediated responses. Using an established murine model that isolates the autoimmune component of graft-versus-host disease, we hypothesized that T-helper type 1 cells would restrict FoxP3-driven regulatory T cells. Upon transfer into immune-deficient syngeneic hosts, alloreactive Tbx21−/−CD4+ T cells led to marked increases in FoxP3+ cells and reduced clinical evidence of autoimmunity. To evaluate whether peripheral induction contributed to regulatory T-cell predominance, we adoptively transferred Tbx21−/− T cells that consisted of fate mapping for FoxP3: recipients of flow-purified effector cells that were Foxp3− and Tbx21−/− had enhanced T-regulatory-cell predominance during autoimmune graft-versus-host disease. These data directly demonstrated that peripheral T-regulatory-cell induction was inhibited by Tbet. Finally, Tbx21−/− T-regulatory cells cross-regulated autoimmune wild-type T-effector-cell cytokine production in vivo. The Tbet pathway therefore directly impairs T-regulatory-cell reconstitution and is consequently a feasible target in efforts to prevent autoimmune graft-versus-host disease.

The major diversification of Vγ1.1+ and Vγ2+ thymocytes in mice occurs after commitment to the γδ T-cell lineage.

γδ T cells are a heterogeneous cell population with different subsets playing specialized and often opposing roles during immune responses. A key question is whether γδ thymocytes are determined for their effector function already at an early stage, before their commitment to the γδ T-cell lineage, or are instructed during their later development. Here, we show that the adult Vγ1.1+ and Vγ2+ γδ T-cell subsets both go through a CD73+ CD24+ development stage, and that the gene regulation involved in lineage commitment is shared by both subsets. We demonstrate that the major subset diversification first occurs after the cells have committed to the γδ T-cell lineage, strongly supporting an instructive model for functional programming of γδ T cells. In conclusion, we show that the two major adult γδ T-cell subsets in mice develop through a shared pathway utilizing similar cellular machinery and that they diverge after the CD24+ CD73+ maturity stage.

Adenovirus-specific T-cell Subsets in Human Peripheral Blood and After IFN-γ Immunomagnetic Selection.

Adoptive antiviral cellular immunotherapy by infusion of virus-specific T cells (VSTs) is becoming an alternative treatment for viral infection after hematopoietic stem cell transplantation. The T memory stem cell (TSCM) subset was recently described as exhibiting self-renewal and multipotency properties which are required for sustained efficacy in vivo. We wondered if such a crucial subset for immunotherapy was present in VSTs. We identified, by flow cytometry, TSCM in adenovirus (ADV)-specific interferon (IFN)-γ+ T cells before and after IFN-γ-based immunomagnetic selection, and analyzed the distribution of the main T-cell subsets in VSTs: naive T cells (TN), TSCM, T central memory cells (TCM), T effector memory cell (TEM), and effector T cells (TEFF). In this study all of the different T-cell subsets were observed in the blood sample from healthy donor ADV-VSTs, both before and after IFN-γ-based immunomagnetic selection. As the IFN-γ-based immunomagnetic selection system sorts mainly the most differentiated T-cell subsets, we observed that TEM was always the major T-cell subset of ADV-specific T cells after immunomagnetic isolation and especially after expansion in vitro. Comparing T-cell subpopulation profiles before and after in vitro expansion, we observed that in vitro cell culture with interleukin-2 resulted in a significant expansion of TN-like, TCM, TEM, and TEFF subsets in CD4IFN-γ T cells and of TCM and TEM subsets only in CD8IFN-γ T cells. We demonstrated the presence of all T-cell subsets in IFN-γ VSTs including the TSCM subpopulation, although this was weakly selected by the IFN-γ-based immunomagnetic selection system.

Molecular Characterization of Human Skin Response to Diphencyprone at Peak and Resolution Phases: Therapeutic Insights

Diphencyprone (DPCP) is a hapten that induces delayed-type hypersensitivity (DTH) reactions. It is used as an immune modulating therapeutic, but its molecular effects in human skin are largely unknown. We studied cellular and molecular characteristics of a recall response to 0.04% DPCP at 3 day (peak) and 14 day (resolution) timepoints using immune markers, RT-PCR and gene array approaches. A peak response showed modulation of ~7,500 mRNA transcripts, with high expression of cytokines that define all major effector T-cell subsets. Concomitant increases in T-cell and CD11c+ dendritic cell (DC) infiltrates were measured. The resolution reaction was characterized by unexpectedly high levels of T-cells and mature (DC-LAMP+) DCs, but with marked decreases in expression of IL-2, IFNγ, and other T-cell derived cytokines. However, negative immune regulators such as IDO1 that were high in peak reactions, continued to have high expression in resolution reactions. In the resolution reaction, ~1,500 mRNA transcripts were significantly different from placebo-treated skin. These data suggest the response to DPCP evolves from an inflammatory/effector peak at day 3 to a more regulated immune response after 14 days. This model system could be useful for further dissection of mechanisms of immune activation or negative immune regulation in human skin.

Role of IL-10-Producing Regulatory B Cells in Chronic Hepatitis B Virus Infection.

A subset of interleukin (IL)-10-producing regulatory B (Breg) cells that suppress T-cell-mediated immunity was recently identified; however, their role in chronic hepatitis B (CHB) remains elusive. To explore the possible role of Breg in the interaction with Th cells and consequent pathogenesis of CHB. The prevalence of Breg as well as 3 major effector T-cell subsets--CD4(+)CD25(high)Foxp3(+) regulatory T (Treg) cells, T helper 1 cells (Th1), and T helper 2 cells (Th2)--was assessed in the peripheral blood of 31 patients with CHB, 28 patients with acute hepatitis B (AHB), and 25 healthy controls (HC). Compared to patients with AHB and HC, the prevalence of Breg and Treg cells and the concentration of IL-10 in the supernatant of cultured peripheral blood mononuclear cells (PBMCs) were greatly increased in patients with CHB. A significantly decreased proportion of Th1 cells was also observed in patients with CHB and was demonstrated to have a negative correlation with the prevalence of Breg. Furthermore, depletion of Treg cells in the PBMCs of patients with CHB did not alter the frequency of Breg cells or their ability to produce IL-10, indicating little, if any, impact of Treg cells on the generation and maintenance of Breg cells. Our data indicate that increased Breg cells might be a major source of elevated IL-10 in CHB and represent a critical and independent regulatory force in the development of impaired anti-HBV immunity, consequently contributing to the pathogenesis of CHB.

Phenotypic characterization of canine intestinal intraepithelial lymphocytes in dogs with inflammatory bowel disease.

BackgroundMany dogs suffering from inflammatory bowel disease (IBD) are presented to veterinary clinics. These patients are diagnosed based on a history of chronic gastrointestinal signs and biopsy‐confirmed histopathologic intestinal inflammation. Intestinal intraepithelial lymphocytes (IEL) are part of the first line of defense in the gastrointestinal immune system. Alterations in IEL subsets may play a role in the pathogenesis of IBD.HypothesisThe aim of this study was to characterize the phenotypes of IEL in dogs with IBD compared with healthy control dogs.AnimalsIntestinal intraepithelial lymphocytes subpopulations of control dogs (n = 5) obtained from endoscopic biopsies (EB) were compared to those obtained from full thickness biopsies (FTB) on the same day. In addition, the phenotypes of IEL from FTB of control dogs (n = 10) were compared with EB of IBD dogs (n = 10). Each participant was scored clinically using the canine inflammatory bowel disease activity index (CIBDAI), and all samples were graded histopathologically. Three‐color flow cytometry of isolated IEL was performed using monoclonal antibodies against T‐ and B‐lymphocyte subpopulations.ResultsNo significant differences in the composition of IEL subpopulations were found in control dogs based on method of biopsy. The IBD dogs had significantly higher CIBDAI and histopathologic scores compared with control dogs and their IEL contained a significantly higher frequency TCRγδ T‐cells.Conclusions and Clinical ImportanceEndoscopic biopsies provide suitable samples for 3‐color flow cytometry when studying canine intestinal IEL and IBD patients show significant changes of major T‐cell subsets compared to healthy control dogs.

CD8(+) T-Cell Responses in Acute Hepatitis C Virus Infection.

Hepatitis C virus (HCV) infects approximately 170 million people worldwide and is a major cause of life-threatening liver diseases such as liver cirrhosis and hepatocellular carcinoma. Acute HCV infection often progresses to chronic persistent infection, although some patients recover spontaneously. The divergent outcomes of acute HCV infection are known to be determined by differences in virus-specific T-cell responses among patients. Of the two major T-cell subsets, CD8+ T-cells are known to be the key effector cells that control viral infections via cytolytic activity and cytokine secretion. Herein, we review various aspects of HCV-specific CD8+ T-cell responses in acute HCV infection. In particular, we focus on timing of CD8+ T-cell responses, relationship between CD8+ T-cell responses and outcomes of acute HCV infection, receptor expression on CD8+ T-cells, breadth of CD8+ T-cell responses, and viral mutations.

Androgens Contribute to Age-Associated Changes in Peripheral T-Cell Homeostasis Acting in a Thymus-Independent Way

Objective: Considering a causal role of androgens in thymic involution, age-related remodeling of peripheral T-cell compartments in the absence of testicular hormones was evaluated. Methods: Rats were orchidectomized (ORX) at the age of 1 month, and T-peripheral blood lymphocytes (PBLs) and splenocytes from young (75-day-old) and aged (24-month-old) rats were examined for differentiation/activation and immunoregulatory marker expression. Results: In ORX rats, following the initial rise, the counts of CD4+ and CD8+ PBLs diminished with aging. This reflected the decline in thymic export as shown by recent thymic emigrant (RTE) enumeration. Orchidectomy increased the count of both of the major T-splenocyte subsets in young rats, and they (differently from controls) remained stable with aging. The CD4+:CD8+ T-splenocyte ratio in ORX rats shifted towards CD4+ cells compared to age-matched controls. Although in the major T-cell subsets in the blood and spleen from aged ORX rats the numbers of RTEs were comparable to the corresponding values in age-matched controls, the numbers of mature naïve and memory/activated cells substantially differed. Compared with age-matched controls, in aged ORX rats the numbers of CD4+ mature naïve PBLs and splenocytes were reduced, whereas those of CD4+ memory/activated cells (predictive of early mortality) were increased. Additionally, in spleens from aged ORX rats, despite unaltered thymic export, CD4+CD25+FoxP3+ and natural killer T cell counts were greater than in age-matched controls. Conclusion: (i) Age-related decline in thymopoietic efficacy is not dependent on androgen presence, and (ii) androgens are involved in the maintenance of peripheral T-cell (particularly CD4+ cell) homeostasis during aging.

IL-13/IL-22–coproducing T cells, a novel subset, are increased in atopic dermatitis

Atopic dermatitis (AD) is a chronic, relapsing, inflammatory skin disease. A considerable body of evidence has shown that TH2 cells that produce IL-4 and IL-13 play a central role in the pathogenesis of AD, although TH1 cells that produce IFN-γ also contribute to the chronic phase of AD.1 Recently, IL-22 was shown to be upregulated in AD.2,3 In AD, IL-22 is thought to be primarily secreted by TH22 cells that do not coproduce IL-17, IL-4, or IFN-γ, suggesting that TH2 and TH22 cells are the major T-cell subsets in AD.

The co-receptor BTLA negatively regulates human Vγ9Vδ2 T-cell proliferation: a potential way of immune escape for lymphoma cells

AbstractVγ9Vδ2 cells, the major γδ T-cell subset in human peripheral blood, represent a T-cell subset that displays reactivity against microbial agents and tumors. The biology of Vγ9Vδ2 T cells remains poorly understood. We show herein that the interaction between B- and T-lymphocyte attenuator (BTLA) and herpesvirus entry mediator (HVEM) is a major regulator of Vγ9Vδ2 T-cell proliferation control. BTLA was strongly expressed at the surface of resting Vγ9Vδ2 T cells and inversely correlated with T-cell differentiation. BTLA-HVEM blockade by monoclonal antibodies resulted in the enhancement of Vγ9Vδ2 T-cell receptor–mediated signaling, whereas BTLA-HVEM interaction led to a decrease in phosphoantigen-mediated proliferation by inducing a partial S-phase arrest. Our data also suggested that BTLA-HVEM might participate in the control of γδ T-cell differentiation. In addition, the proliferation of autologous γδ T cells after exposition to lymphoma cells was dramatically reduced through BTLA-HVEM interaction. These data suggest that HVEM interaction with BTLA may play a role in lymphomagenesis by interfering with Vγ9Vδ2 T-cell proliferation. Moreover, BTLA stimulation of Vγ9Vδ2 T cells appears as a new possible mechanism of immune escape by lymphoma cells.

IL‐12‐mediated STAT4 signaling and TCR signal strength cooperate in the induction of CD40L in human and mouse CD8+T cells

CD40L is one of the key molecules bridging the activation of specific T cells and the maturation of professional and nonprofessional antigen-presenting cells including B cells. CD4(+) T cells have been regarded as the major T-cell subset that expresses CD40L upon cognate activation; however, we demonstrate here that a putative CD8(+) helper T-cell subset expressing CD40L is induced in human and murine CD8(+) T cells in vitro and in mice immunized with antigen-pulsed dendritic cells. IL-12 and STAT4-mediated signaling was the major instructive cytokine signal boosting the ability of CD8(+) T cells to express CD40L both in vitro and in vivo. Additionally, TCR signaling strength modulated CD40L expression in CD8(+) T cells after primary differentiation in vitro as well as in vivo. The induction of CD40L in CD8(+) T cells regulated by IL-12 and TCR signaling may enable CD8(+) T cells to respond autonomously of CD4(+) T cells. Thus, we propose that under proinflammatory conditions, a self-sustaining positive feedback loop could facilitate the efficient priming of T cells stimulated by high affinity peptide displaying APCs.

Key implication of CD277/butyrophilin-3 (BTN3A) in cellular stress sensing by a major human γδ T-cell subset

AbstractHuman peripheral Vγ9Vδ2 T cells are activated by phosphorylated metabolites (phosphoagonists [PAg]) of the mammalian mevalonate or the microbial desoxyxylulose-phosphate pathways accumulated by infected or metabolically distressed cells. The underlying mechanisms are unknown. We show that treatment of nonsusceptible target cells with antibody 20.1 against CD277, a member of the extended B7 superfamily related to butyrophilin, mimics PAg-induced Vγ9Vδ2 T-cell activation and that the Vγ9Vδ2 T-cell receptor is implicated in this effect. Vγ9Vδ2 T-cell activation can be abrogated by exposing susceptible cells (tumor and mycobacteria-infected cells, or aminobisphosphonate-treated cells with up-regulated PAg levels) to antibody 103.2 against CD277. CD277 knockdown and domain-shuffling approaches confirm the key implication of the CD277 isoform BTN3A1 in PAg sensing by Vγ9Vδ2 T cells. Fluorescence recovery after photobleaching (FRAP) experiments support a causal link between intracellular PAg accumulation, decreased BTN3A1 membrane mobility, and ensuing Vγ9Vδ2 T-cell activation. This study demonstrates a novel role played by B7-like molecules in human γδ T-cell antigenic activation and paves the way for new strategies to improve the efficiency of immunotherapies using Vγ9Vδ2 T cells.

Role of ovarian hormones in T-cell homeostasis: From the thymus to the periphery

The study explored the putative role of ovarian hormones in the peripubertal remodelling of peripheral T-cell compartment. Ovariectomy at age of 1 month enhanced the peripubertal rise in CD4+ and CD8+ cell numbers in peripheral blood (PB) and spleen from 2-month-old rats. This reflected maintenance of thymopoietic efficiency at the prepubertal level (judging by numbers of the most mature CD4+ and CD8+ thymocytes and recent thymic emigrants) and alterations in T-cell survival/proliferation in the periphery. Compared with age-matched controls, the frequency of apoptotic cells among CD8+ peripheral blood lymphocytes (PBLs) and CD4+ and CD8+ splenocytes was diminished in ovariectomized (Ox) rats, at least partly, due to lower CD95 surface density. The diminished frequency of the apoptotic T splenocytes could also be associated with the rise in the amount of splenic IL-7 mRNA. Additionally, the latter finding was consistent with the augmented proliferation of CD4+ and CD8+ splenocytes. However, the enhanced proliferation of these cells could also be linked to the rise in IL-2 receptor surface density. This increase was related to the enhanced splenic TNF-α mRNA expression. Additionally, ovariectomy led to the phenotypic alterations in the major PBL and splenic T-cell subsets by diminishing/preventing the peripubertal changes in the frequency of cells at distinct stages of post-thymic differentiation/maturation (recent thymic emigrants, mature naïve and memory cells), and by decreasing the frequency of NKT cells within peripheral CD8+ subsets. In addition to numerical and phenotypic changes in T-cell compartment (due to the lack of ovarian hormone action at both the thymic and peripheral level), Ox rats exhibited a much larger delayed-type hypersensitivity (DTH) response compared with age-matched controls. This suggested the augmented T-cell-mediated immune response in Ox rats compared with aged-matched controls.

Differentiation, phenotype, and function of interleukin-17–producing human Vγ9Vδ2 T cells

AbstractIn healthy adults, the major peripheral blood γδ T-cell subset expresses the Vγ9Vδ2 TCR and displays pleiotropic features. Here we report that coculture of naive Vγ9Vδ2 T cells with phosphoantigens and a cocktail of cytokines (IL-1-β, TGF-β, IL-6, and IL-23), leads to selective expression of the transcription factor RORγt and polarization toward IL-17 production. IL-17+ Vγ9Vδ2 T cells express the chemokine receptor CCR6 and produce IL-17 but neither IL-22 nor IFN-γ; they have a predominant terminally differentiated (CD27−CD45RA+) phenotype and express granzyme B, TRAIL, FasL, and CD161. On antigen activation, IL-17+ Vγ9Vδ2 T cells rapidly induce CXCL8-mediated migration and phagocytosis of neutrophils and IL-17–dependent production of β-defensin by epithelial cells, indicating that they may be involved in host immune responses against infectious microorganisms. Accordingly, an increased percentage of IL-17+ Vγ9Vδ2 lymphocytes is detected in the peripheral blood and at the site of disease in children with bacterial meningitis, and this pattern was reversed after successful antibacterial therapy. Most notably, the phenotype of IL-17+ Vγ9Vδ2 T cells in children with meningitis matches that of in vitro differentiated IL-17+ Vγ9Vδ2 T cells. Our findings delineate a previously unknown subset of human IL-17+ Vγ9Vδ2 T lymphocytes implicated in the pathophysiology of inflammatory responses during bacterial infections.

A Comprehensive Comparison Immune Recovery In Adult Patients Following Allogeneic Umbilical Cord Blood, Matched Sibling and Matched Unrelated Donor Stem Cell Transplantation

AbstractAbstract 2313Immunologic reconstitution following stem cell transplantation (SCT) arises from thymic-independent peripheral expansion of memory T-cells transplanted with the stem cell graft, and thymic-dependent maturation of stem cell derived lymphoid progenitor cells. As a consequence of thymic involution, adult stem cell transplant recipients rely largely upon the thymic-independent pathway. This process is facilitated by a plentiful supply of mature T-cells contained within peripheral blood or bone marrow grafts. Umbilical cord blood (UCB) grafts contain predominantly naive T-cells thereby limiting the potential for thymic-independent immune recovery. Recent reports have documented slow immune recovery in adult UCB recipients, however it has yet to be described in the context of a comparable population of adult allogeneic matched sibling or unrelated donor SCT. Methods:Between 2007 and 2009, we characterized cellular immune reconstitution in a consecutive cohort of adult patients undergoing myeloablative SCT using either matched sibling (MSD), matched unrelated donor (MUD) peripheral blood stem cell (PBSC) or dual UCB donor grafts. Dual UCB transplant recipients were conditioned with TBI 1350cGy and fludarabine 160mg/m2 (Flu). PBSC recipients were conditioned with either TBI 1350cGy or IV busulfan 12.8mg/kg (Bu) and cyclophosphamide 120mg/kg, or Bu/Flu. PBSC grafts were allele-level matched at HLA-A, B, C and DRB1. UCB grafts were mismatched at no more than 2 class I or class II loci. Both cohorts received GvHD prophylaxis with Tacrolimus for at least 6 months. UCB recipients received mycophenolate mofetil 2g/day for at least 60 days instead of standard dose methotrexate GvHD prophylaxis for PBSC recipients. Quantification of the following lymphoid subsets were performed by flow cytometry on fresh peripheral blood prior to, and then at approximately 45, 100, 180, and 360 days following transplantation: NK and NKT cells, B-cells, plasmacytoid dendritic cells, CD3+, CD4+, CD8+, regulatory and na•ve T-cells. T-cell receptor excision circles (sjTREC) were quantified by real time PCR on DNA collected from an isolated fraction of CD3+ T-cells. Cumulative corticosteroid usage prior to day 100 (as determined by area under the curve) was determined as a method for comparing acute GvHD severity. The Kruskal-Wallis test with adjustments for multiple comparisons was used compare immune recovery values at 45, 100, 180 and 360 days post transplantation. The PearsonÕs Chi-square test was used to compare the CMV reactivation rate of UCB to MSD/MUD. Results:Forty-two recipients of allogeneic SCT (MSD-13, MUD-14, UCB-15) with successful donor engraftment and who survived a minimum of 6 months were evaluated. The MSD, MUD and UCB recipients had a median age of 41, 42 and 31 years, respectively (p = 0.13). There was no significant difference in corticosteroid administration before day 100 or chronic GvHD in the three cohorts (p=0.74). There were no differences in the kinetics of immune recovery between MSD and MUD recipients. At 45 days following transplantation, UCB recipients had significantly lower levels of CD4+ (figure), CD8+ and NKT-cells. By day 100, UCB recipients had similar numbers of CD4+ T-cells, but remained lower in the other major T-cell subsets. By day 180 however, all T-cell subsets except NKT cells (p=0.033) were similar to the MSD/MUD recipients. NK cell recovery was faster in the UCB recipients (figure). There was also no difference in B-cell recovery among the 3 cohorts. TREC levels were not significantly different in recipients of all graft types, but were uniformly low (figure). The slow recovery of T-cells in the UCB cohort corresponds with a higher Kaplan-Meier estimate of CMV reactivation compared to the MSD/MUD cohort (90% vs. 36%; p = 0.0078). Conclusion:Compared to HLA-identical MSD and MUD adult SCT recipients, quantitative lymphoid recovery in UCB transplant recipients is slower in the first two months, but these differences are erased by 4–6 months following transplantation. NK reconstitution is more rapid in UCB recipients. Reduction of early opportunistic infections affecting UCB transplant recipients may arise from effective techniques to boost early T-cell recovery. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

T-Cell Responses and In Vivo Cytotoxicity in the Target Organ and the Regional Lymphoid Tissue During Airborne Infection with the Virulent Mycobacterium tuberculosis MT103 and its Lipid Mutant fadD26

To ascertain the in vivo role of mycobacterial lipids phthiocerol dimycocerosates (PDIM) in experimental murine tuberculosis (Tb), airways infection was used to compare the parental virulent clinical isolate MT103 with its mutant fadD26, lacking PDIM. Lungs were assessed as the Tb-target organ and mediastinal lymph nodes as the corresponding lymphoid tissue, in order to quantify: the major T-cell subsets (CD4+/CD8+/gammadelta+) and their activation kinetics, bacillary burden, and in vivo cytotoxicity against inoculated target cells loaded with mycobacterial Ags. After 4 weeks, infection augmented total and activated CD4+ and CD8+ T cells in lungs and nodes mainly with MT103, while gammadelta+ T cells increased earlier in nodes. MT103 bacillary burden was bigger and appeared earlier than the mutant fadD26, especially in the lung than in mediastinal nodes. At day 14 of MT103 infection, there was no cytotoxicity in lungs and nodes; while with fadD26 there was some in the nodes. At day 21 of MT103 infection, important cytotoxicity was detected only in lungs; while with fadD26 both tissues showed important activity. Interestingly, unlike the infection with fadD26, cytotoxicity under MT103 fell considerably in the target organ (lung) from days 21 to 60, the advanced phase. Although upon airways infection both mycobacteria behaved similarly regarding T cell (CD4/CD8/gammadelta) stimulation kinetics; they differed in the magnitude of these responses, in the bacterial load within tissues, and to trigger in vivo cytotoxicity in lungs and regional lymph nodes. This highlights the relevance of certain mycobacterial lipids to modify crucial effector branches of immunity.

Role of ovarian hormones in age-associated thymic involution revisited

A commonly held view that ovarian hormones are causally involved in age-associated thymic involution has been recently challenged. In particular, their relevance in the progression of thymic involution has been disputed. To reassess this issue 10-month-old rats with well advanced thymic involutive changes were ovariectomized (Ovx), and after 1 month thymic cellularity, thymocyte development and levels of recent thymic emigrants (RTEs) were examined in peripheral blood and spleen. In addition, the distribution of major conventional and regulatory T-cell subsets was analyzed in the same peripheral lymphocyte compartments. Ovariectomy increased thymic weight and cellularity above the levels in both 10-month-old and age-matched controls indicating that ovarian hormone ablation not only prevented further progression of thymic involution, but also reversed it. The increased thymic cellularity was accompanied by altered thymocyte differentiation/maturation culminating in increased thymic output of naïve T cells as indicated by elevated levels of both CD4+ and CD8+ RTEs in peripheral blood and spleen. The changes in T-cell development produced: (i) a disproportional increase in cellularity across thymocyte subsets, so that relative proportions of cells at all maturational stages preceding the CD4+CD8+ T cell receptor (TCR)alphabeta(low) stage were reduced; the relative numbers of CD4+CD8+ TCRalphabeta(low) cells entering positive selection and their immediate CD4+CD8+ TCRalphabeta(high) descendents were increased, while those of the most mature CD4+CD8- and CD4-CD8+ TCRalphabeta(high) cells remained unaltered; (ii) enhanced cell proliferation across all thymocyte subsets and (iii) reduced apoptosis of cells within the CD4+CD8+ thymocyte subset. The augmented thymic output of naïve T cells in Ovx rats most likely reflected an early disinhibition of thymocyte development followed by increased positive/reduced negative selection, at least partly, due to raised thymocyte surface Thy-1 expression. The greater number of CD4+CD25+Foxp3+ cells in both thymus and peripheral blood suggested augmented thymic production of these cells. In addition, an increased CD4+/CD8+ cell ratio was found in the spleen of Ovx rats. Thus, ovarian hormone ablation led not only to increased diversity of the T-cell repertoire, but also to a new balance among distinct T-cell subsets in the periphery.

Cellular immunity of patients with malignant glioma: prerequisites for dendritic cell vaccination immunotherapy

Vaccination therapy that uses dendritic cells (DCs) is a promising immunotherapeutic approach. However, it relies on intact cellular immunity and efficient generation of mature DCs, both of which can be impaired in patients with glioma. Therefore, the immune status and ex vivo generation of DC in such patients were studied. The frequencies of white blood cell subsets and monocyte-derived, mature DCs in patients with high-grade gliomas and healthy control volunteers were analyzed using flow cytometry. In the patients, frequencies of lymphocytes, T cells, and B cells were reduced in comparison with the volunteers in the control group, whereas frequencies of neutrophils and monocytes were increased. There were no differences between the two groups in terms of white blood cell counts or the frequency of NK cells and the major T-cell subsets. The responsiveness of T cells to lectin stimulation was normal. For monocytes, lower frequencies of CD80+ and CD86+ cells but not of CD40+ and HLA-DR+ cells were observed in patients. Ex vivo DC generation in a two-step culture protocol in autologous plasma-supplemented medium or in serum-free medium showed only minor differences in CD80 and HLA-DR expression between the patient and control groups. Frequencies of CD83+, CD1a+, CD14-, CD40+, and CD86+ cells were comparable. Overall, the serum-free medium was superior to the plasma-supplemented medium and allowed efficient ex vivo generation of CD83+, CD1a+, and CD14- mature DCs. Only minor defects in the immune status of patients with glioma were observed, which probably would not hamper immunotherapy. Mature DCs can be generated successfully in normal numbers and with typical immunophenotypes from monocytes of patients with glioma, particularly under serum-free conditions.