The imbalance of T helper 17/regulatory T cells and memory B cells during the early post‐transplantation period in peripheral blood of living donor liver transplantation recipients under calcineurin inhibitor‐based immunosuppression

There is limited clinical research regarding the changes in peripheral lymphocyte subsets during the early post-operative period of liver transplantation. Serial changes of T cells and B cells in living donor liver transplantation (LDLT) recipients during the early post-transplantion period were prospectively investigated. From June 2010 to February 2011, 27 consecutive LDLT recipients were enrolled. Percentages of T helper type 1 (Th1; interferon-γ-producing), Th2 (interleukin-4-producing), Th17 (interleukin-17-producing), regulatory T (Treg; CD4⁺ CD25⁺ FoxP3⁺), memory B (CD19⁺ CD24^hi CD38⁻) and mature B (CD19⁺ CD24^int CD38^int) cells were measured using fluorescence-activated cell sorting. Patients were followed up for a median of 9·9 months (range 6·8−15·5 months) after transplantation. Serial monitoring of immunological profiles showed no significant suppression of Th1, Th2, Th17, mature B or memory B cells, whereas frequencies of Treg cells significantly decreased. Interleukin-17 production by central and effector memory cells was not suppressed during the early post-operative period. The continuous production of interleukin-17 by the memory T cells may contribute to the persistence of Th17 cells. This prospective study demonstrated that current immunosuppression maintained the effector T or memory B cells during the early post-transplantation period but significantly suppressed Treg cells. Serial immune monitoring may suggest clues for optimal or individualized immunosuppression during the early post-operative period in clinical practice.     

Regular monitoring of cytomegalovirus-specific cell-mediated immunity in intermediate-risk kidney transplant recipients: predictive value of the immediate post-transplant assessment

Objective

Previous studies on monitoring of post-transplant cytomegalovirus (CMV)-specific cell-mediated immunity (CMI) are limited by single-centre designs and disparate risk categories. We aimed to assess the clinical value of a regular monitoring strategy in a large multicentre cohort of intermediate-risk kidney transplant (KT) recipients.

Should IFN-γ, IL-17 and IL-2 be considered predictive biomarkers of acute rejection in liver and kidney transplant? Results of a multicentric study

Acute rejection (AR) remains a major challenge in organ transplantation, and there is a need for predictive biomarkers. In the present multicenter study, we prospectively examined a series of biomarkers in liver and kidney recipients. Intracellular expression of IFN-γ, IL-17 and IL-2 and IL-17 soluble production were evaluated both pre-transplantation and post-transplantation (1st and 2nd week, 1st, 2nd and 3rd month). 142 transplant patients (63 liver/79 kidney) were included in the study. Twenty-eight recipients (14 liver/14 kidney) developed AR. Pre- and post-transplantation intracellular expression of %IFN-γ⁺ in CD4⁺CD69⁺ and in CD8⁺CD69⁺ and soluble IL17 identified liver and kidney transplant patients at high risk of AR. Pre-transplantation, %IL-2⁺ in CD8⁺CD69⁺ also identified kidney patients at high risk. We constructed pre- and post-transplantation risk prediction models, based on a composite panel of biomarkers, which could provide the basis for future studies and will be a useful tool for the selection and adjustment of immunosuppressive treatments.     

CD8+ T cells and not CD4+ T cells are hyporesponsive to CD28- and CD40L-mediated activation in HIV-infected subjects

T cell dysfunction in HIV-infected subjects could be the consequence of altered sensitivity of CD4⁺ or CD8⁺ T cells to various costimulatory signals. Therefore, we studied proliferation and cytokine production in highly purified CD8⁺ and CD4⁺ T cells from HIV-infected and HIV⁻ subjects, induced by co-activation via cell-bound CD80, CD86 and CD40 or by allo-activation. Regardless of the nature of the first and the costimulatory signal, CD8⁺ T cells from patients proliferated consistently less than controls, while responses from CD4⁺ T cells were similar in patients and controls. This phenomenon was observed after ligation of CD28 combined with anti-CD3 or phorbol myristate acetate (PMA), but also after allogeneic stimulation and after activation by CD40 and anti-CD3. Anti-CD3 combined with CD80 or CD86 induced a mixed Th1/Th2-type cytokine profile in both CD4⁺ and CD8⁺ T cells from controls, whereas anti-CD3 plus CD40 induced only low levels of Th2-type cytokines and no interferon-gamma (IFN-γ) in CD4⁺ T cells. Compared with controls, CD4⁺ T cells from patients produced slightly lower levels of IL-10 but equal amounts of IFN-γ, IL-4 and IL-5, while CD8⁺ T cells from patients produced less of all cytokines tested. In conclusion, responses of purified CD4⁺ T cells from HIV⁺ subjects to various costimulatory pathways are relatively intact, whereas CD8⁺ T cells are hyporesponsive at the level of proliferation and cytokine production. A generalized intrinsic CD8⁺ T cell failure might contribute to viral and neoplastic complications of HIV infection.     

Anomalies of the CD8+ T cell pool in haemochromatosis: HLA-A3-linked expansions of CD8+CD28− T cells

The present study consists of a phenotypic and functional characterization of peripheral blood T lymphocytes in a group of 21 patients with hereditary haemochromatosis (HH), an MHC class I-linked genetic disease resulting in iron overload, and a group of 30 healthy individuals, both HLA-phenotyped. The HH patients studied showed an increased percentage of CD8⁺ CD28⁻ T cells with a corresponding reduction in the percentage of CD8⁺ CD28⁺ T cells in peripheral blood relative to healthy blood donors. No anomalies of CD28 expression were found in the CD4⁺ subset. The presence of the HLA-A3 antigen but not age accounted for these imbalances. Thus, an apparent failure of the CD8⁺ CD28⁺ T cell population ‘to expand’, coinciding with an ‘expansion’ of CD8⁺ CD28⁻ T cells in peripheral blood of HLA-A3⁺ but not HLA-A3⁻ HH patients was observed when compared with the respective HLA-A3-matched control group. A significantly higher percentage of HLA-DR⁺ but not CD45RO⁺ cells was also found within the peripheral CD8⁺ T cell subset in HH patients relative to controls. Phytohaemagglutinin (PHA) stimulation of peripheral blood mononuclear cells (PBMC) for 5 days showed: (i) that CD8⁺ CD28⁺ T cells both in controls and HH were able to expand in vitro; (ii) that CD8⁺ CD28⁻ T cells decreased markedly after activation in controls but not in HH patients. Moreover, functional studies showed that CD8⁺ cytotoxic T lymphocytes (CTL) from HH patients exhibited a diminished cytotoxic activity (approx. two-fold) in standard ⁵¹Cr-release assays when compared with CD8⁺ CTL from healthy controls. The present results provide additional evidence for the existence of phenotypic and functional anomalies of the peripheral CD8⁺ T cell pool that may underlie the clinical heterogeneity of this iron overload disease. They are of particular relevance given the recent discovery of a novel mutated MHC class I-like gene in HH.     

Depletion of γδ+ T cells increases CD4+ FoxP3 (T regulatory) cell response in coxsackievirus B3-induced myocarditis

Coxsackievirus B3 (CVB3) causes severe myocarditis in BALB/c mice which depends upon CD4⁺ T helper type 1 [Th1; i.e. interferon-γ⁺ (IFN-γ⁺)] and γδ⁺ cells. Depleting γδ⁺ cells using anti-γδ antibody suppresses myocarditis and CD4⁺ IFN-γ⁺ cell numbers in the spleen and heart of infected mice while increasing CD4⁺ FoxP3⁺ cells. Mice deficient in γδ⁺ cells have increased numbers of naïve (CD44^lo CD62L^hi) and fewer effector (CD44^hi CD62^lo) memory CD4⁺ cells than infected γδ⁺-cell-sufficient mice. Virus neutralizing antibody titres are not significantly different between γδ⁺ T-cell-sufficient and -deficient animals. To confirm that the memory cell response differs in acutely infected mice lacking γδ⁺ cells, CD4⁺ cells were purified and adoptively transferred into naïve recipients, which were rested for 4 weeks then infected with CVB3. Recipients given either 0·5 × 10⁶ or 1·0 × 10⁶ CD4⁺ from infected donors developed over twice the severity myocarditis and 10-fold less cardiac virus titre compared with recipients given equivalent numbers of CD4⁺ cells from infected and γδ⁺-cell-depleted donor animals. Additionally, to show that more functionally active T regulatory cells are present in γδ⁺ T-cell-depleted mice, CD4⁺ CD25⁺ and CD4⁺ CD25⁻ cells were isolated and adoptively transferred into infected recipients. Mice receiving CD4⁺ CD25⁺ cells from γδ⁺ T-cell-depleted donors developed significantly less myocarditis and CD4⁺ Th1 cell responses compared with mice receiving equal numbers of CD4⁺ CD25⁺ cells from infected γδ⁺ T-cell-sufficient animals. This study shows that γδ⁺ cells promote CD4⁺ IFN-γ⁺ acute and memory responses by limiting FoxP3⁺ T regulatory cell activation.     

CD4+ T cell-mediated rejection of major histocompatibility complex class I-disparate grafts: A role for alloantibody

Experimental studies of the T cell requirement for rejection of class I major histocompatibility complex (MHC)-disparate grafts have generated controversy over both the autonomy of CD8⁺ T cells and the mechanism whereby CD4⁺ T cells are able to independently mediate rejection. In this study of rejection of RT1A^a class I MHC-disparate rat cardiac and skin allografts by high-responder PVG RT1^u recipients, we show that elimination of CD8⁺ T cells [by anti-CD8 monoclonal antibody (mAb) administration in vivo] fails to prolong graft survival, whereas partial depletion of CD4⁺ T cells (by anti-CD4 mAb treatment) markedly delays rejection of class I-disparate heart grafts, and marginally prolongs survival of skin grafts. Anti-CD4-treated PVG-RT1^u athymic nude rats reconstituted with CD8⁺ T cells failed to reject class I-disparate skin grafts for several weeks and eventual rejection correlated with re-emergence of a small number of donor derived CD4⁺ T cells. Conversely, anti-CD8-treated nude rats reconstituted with CD4⁺ T cells alone rapidly rejected class I-disparate skin grafts. Passive transfer of anti-class I immune serum to anti-CD4-treated euthymic recipients promptly restored their ability to specifically reject a class I-disparate heart graft. Similarly, passive transfer of immune serum to PVG-RT1^u nude rats bearing skin allografts caused destruction of class I-disparate but not third-party grafts. These results demonstrate that CD4⁺ T cells are both necessary and sufficient to cause rejection of class I-disparate heart and skin grafts in this model and that CD4⁺ T cell-dependent alloantibody plays a decisive role in effecting rejection.     

Characteristics of Expanded CD4+CD28null T Cells in Patients with Chronic Hepatitis B

Expanded CD4⁺CD28^null T cells have not been described in the circulation of patients with chronic hepatitis B (CHB). The aim of the present was to detect and characterize the surface phenotype and functional capacity of these cells in CHB patients. Expanded CD4⁺CD28^null T cells were detected in the circulation of CHB patients with high viral load and elevated aminotransferase levels. Most CD4⁺CD28^null T cells showed a CD27?CD45RA^?CD45RO⁺ surface phenotype. The markers CD56, CD57 and killer immunoglobulin-like receptor (KIR) were detected on CD4⁺CD28^null T cells, but the majority were positive for CD57. Functionally, CD4⁺CD28^null T cells were found to be potent cytotoxic T lymphocytes with perforin and granzyme B secretion profiles. These findings indicate that the expanded CD4⁺CD28^null T cells are cytotoxic memory T cells and display a distinct functional phenotype in comparison with CD4⁺CD28⁺ T cells. The presence of these cells appears to be associated with inflammatory conditions, suggesting that these elevated CD4⁺CD28^null T cells might be involved in the pathogenesis of CHB.     

CD28<Superscript>neg.</Superscript> T lymphocytes of a melanoma patient harbor tumor immunity and a high frequency of germline-encoded and public TCRs

Increased numbers of CD8⁺CD28^neg. T cells have been detected in the peripheral blood of patients with several types of malignancies. However, the role of these cells in anticancer immunity are not yet clear and CD8⁺CD28^neg. T cells are a controversially discussed subpopulation reported both as immunosuppressive and cytotoxic. In this study, we examined the T cell receptor (TCR) repertoire and complementarity-determining region 3 sequences of CD28^neg. T cells in a melanoma patient with recurrent disease who achieved long-term disease-free status. As a result, the patient’s oligoclonal CD8⁺CD28^neg. T cell compartment holds TCRs that are public and specific for Melan-A as well as several public TCRs reported for common viral antigens. While over 80% of his CD8⁺CD28^neg. T cells expressed a cytotoxicity marker, CD57, only 0.01% of CD8⁺ CD28^neg. T cells were positive for Foxp3. In conclusion, our results demonstrate that besides virus-specific also tumor-associated self-antigen targeting T cells accumulate in the CD28^neg. compartment of the immunological memory. Since the patient is in ongoing complete remission for more than 9 years, CD8⁺CD28^neg. T cells with the Melan-A-specific TCR might contribute to antitumor immunity in this patient.     

Elevated granzyme M-expressing lymphocytes during cytomegalovirus latency and reactivation after allogeneic stem cell transplantation

Human cytomegalovirus (HCMV) reactivation can cause serious complications in allogeneic stem cell transplantation (SCT) patients. HCMV is controlled by cytotoxic lymphocytes that release antiviral granzymes. Recently, we have demonstrated that granzyme M (GrM) inhibits HCMV replication in vitro, however the physiological role of GrM and its cellular distribution during HCMV infection remains unknown. Here, we examined GrM expression in lymphocyte populations during HCMV infection. The percentage of GrM-expressing effector-memory CD4⁺ T-cells was higher in HCMV latently-infected healthy individuals compared to that of uninfected individuals. SCT recipients had higher percentages of GrM-expressing CD4⁺ T, CD8⁺ T, γδT, and NKT cells. Despite lower total T-cell numbers, HCMV reactivation in SCT patients specifically associated with higher percentages of GrM-expressing CD4⁺ (total and central-memory) T-cells. GrM was elevated in plasma during HCMV reactivation, pointing to extracellular perforin-independent functions of GrM. We conclude that GrM may be important in regulating HCMV latency and reactivation in SCT patients.     

Growth and Differentiation Advantages of CD4+OX40+ T Cells from Allogeneic Hematopoietic Stem Cell Transplantation Recipients

OX40 (CD134), an activation-induced costimulatory molecule, is mainly expressed on CD4⁺ T cells. Several reports, including previous reports from our laboratory, suggest that OX40-mediated signaling plays an important role in the development of graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (Allo HSCT). Here, we show that peripheral blood CD4⁺OX40⁺ T cells are a unique cell subset as they possess the homing receptors of lymph nodes, and some of them have an exceptional capacity to produce high levels of interleukin-2 (IL-2) upon the stimulation through T cell receptors. Stimulation with IL-7 acts selectively on CD4⁺OX40⁺ T cells not only to induce antigen-independent growth but also to increase the frequency of cells with IL-2-producing potential. Simultaneous, but not sequential, ligation of the T cell receptor and OX40 induces CD4⁺OX40⁺ T cells to produce far more IL-2, which causes them to proliferate abundantly and differentiate readily into Th1- or Th2-biased effector memory T cells, especially in Allo HSCT recipients. Although not all the CD4⁺OX40⁺ T cells had IL-2-producing capacity, Allo HSCT recipients with chronic GVHD (cGVHD) had a significantly higher frequency of IL-2-producing OX40⁺ cells in their peripheral blood CD4⁺ T cell subset than Allo HSCT recipients without cGVHD. Collectively, CD4⁺OX40⁺ T cells with IL-2-producing potential are expected to be privileged for growth and differentiation in lymph nodes upon antigen presentation, suggesting that they might be involved in the process of inducing or maintaining cGVHD.     

Impact of T Cell Dose on Outcome of T Cell-Replete HLA-Matched Allogeneic Peripheral Blood Stem Cell Transplantation

Data on whether the T cell dose of allogeneic peripheral blood stem cell (PBSC) products influences transplantation outcomes are conflicting. Using the Center for International Blood and Marrow Transplant Research database, we identified 2736 adult patients who underwent first allogeneic PBSC transplantation for acute leukemia or myelodysplastic syndrome between 2008 and 2014 using an HLA-matched sibling donor (MSD) or an 8/8-matched unrelated donor (MUD). We excluded ex vivo and in vivo T cell-depleted transplantations. Correlative analysis was performed between CD3⁺ T cell dose and the risk of graft-versus-host-disease (GVHD), relapse, nonrelapse mortality (NRM), disease-free survival (DFS), and overall survival (OS). Using maximum likelihood estimation, we identified CD3⁺ T cell dose cutoff that separated the risk of acute GVHD (aGVHD) grade II-IV in both the MSD and MUD groups. A CD3⁺ T cell dose cutoff of 14 × 10⁷ cells/kg identified MSD/low CD3⁺ (n = 223) and MSD/high CD3⁺ (n = 1214), and a dose of 15 × 10⁷ cells/kg identified MUD/low CD3⁺ (n = 197) and MUD/high CD3⁺ (n = 1102). On univariate analysis, the MSD/high CD3⁺ group had a higher cumulative incidence of day +100 aGVHD grade II-IV compared with the MSD/low CD3⁺ group (33% versus 25%; P = .009). There were no differences between the 2 groups in engraftment rate, risk of aGVHD grade III-IV or chronic GVHD (cGVHD), NRM, relapse, DFS, or OS. The MUD/high CD3⁺ group had a higher cumulative incidence of day +100 aGVHD grade II-IV compared with the MUD/low CD3⁺ group (49% versus 41%; P = .04). There were no differences between the 2 groups in engraftment rate, risk of severe aGVHD or cGVHD, NRM, relapse, DFS, or OS. Multivariate analysis of the MSD and MUD groups failed to show an association between CD3⁺ T cell dose and the risk of either aGVHD grade II-IV (P = .10 and .07, respectively) or cGVHD (P = .80 and .30, respectively). Subanalysis of CD4⁺ T cells, CD8⁺ T cells, and CD4+/CD8+ ratio failed to identify cutoff values predictive of transplantation outcomes; however, using the log-rank test, the sample size was suboptimal for identifying a difference at this cutoff cell dose. In this registry study, the CD3⁺ T cell dose of PBSC products did not influence the risk of aGVHD or cGVHD or other transplantation outcomes when using an MSD or an 8/8-matched MUD. Subset analyses of CD4⁺ and CD8⁺ T cell doses were not possible given our small sample size.     

Costimulatory molecules in Wegener's granulomatosis (WG): lack of expression of CD28 and preferential up-regulation of its ligands B7-1 (CD80) and B7-2 (CD86) on T cells

T cells are most likely to play an important role in the pathogenesis of WG, and recently a predominant Th1 pattern of immune response has been demonstrated in granulomatous inflammation. Since the expression of costimulatory molecules has a significant impact on the cytokine profile and proliferation response of T cells, the goal of this study was to characterize the expression of costimulatory molecules (CD28, CTLA-4 (CD152), B7-1 (CD80), B7-2 (CD86)) on T cells, monocytes and B cells in WG, and to correlate the findings with clinical parameters such as disease activity, extent and therapy. WG patients (n = 24) and healthy controls (HC; n = 17) were examined for the expression of costimulatory molecules by fluorescence-activated cell sorter analysis, both in whole peripheral blood and after in vitro activation of T cells and antigen-presenting cells. Results were correlated with clinical data. The expression of CD28 on CD4⁺ and CD8⁺ cells was significantly lower in WG than in HC (CD28⁺ 81.4% in WG versus 97.9% of CD4⁺ cells (P < 0.0001); CD28⁺ 44.6% in WG versus 68.5% of CD8⁺ cells (P < 0.00001)), both in peripheral blood and after in vitro activation. A lower percentage of monocytes was B7-2⁺ in WG than in HC in peripheral blood, whereas no significant differences in the expression of B7-1 and B7-2 were observed after in vitro stimulation of monocytes and B cells. After in vitro activation a significantly higher percentage of B7-1⁺ and B7-2⁺ T cells was seen in WG. There was no significant difference in the CTLA-4 expression pattern between WG and HC. The percentage of CD28⁺ lymphocytes correlated negatively with the Disease Extent Index cumulated over the course of disease (r = ?0.46, P = 0.03), indicating a more severe manifestation in patients with lower CD28 expression. Correlations with other clinical parameters such as activity or therapy were not seen. WG patients show a lack of CD28 expression on T cells and an unusual up-regulation of its ligands B7-1 and B7-2 on T cells after in vitro activation as well as a lower expression of B7-2 on freshly isolated monocytes compared with HC. These features might promote the Th1 cytokine pattern and thereby contribute to persistently high levels of immune activation in WG.     

Imbalance of Different Types of CD4+Foxp3+ T cells in renal transplant recipients

Aims: To determine the number of CD4⁺CD25^-Foxp3⁺, CD4⁺CD25⁺Foxp3⁺ and CD4⁺CXCR5⁺Foxp3⁺ T cells in renal transplant recipients that are transplanted stable (TS), or experiencing accelerated rejection (ALR), or acute rejection (AR).

Methods: Renal transplantation was conducted in 28 patients with end-stage renal failure (ESRF). The number of peripheral CD4⁺CD25^-Foxp3⁺, CD4⁺CD25⁺Foxp3⁺, or CD4⁺CXCR5⁺Foxp3⁺ T cells and the serum levels of interleukin-10 (IL-10) were measured in pre- and post-transplant patients and these results were compared to 10 healthy controls (HC). Correlation between CD4⁺CD25⁺Foxp3⁺ and estimated glomerular filtration rate (eGFR), CD4⁺CD25^-Foxp3⁺ and serum creatinine (Cr) levels, or Cr and IL-10 levels in TS patients was also determined.

Results: The number of CD4⁺CD25^-Foxp3⁺ T cells was significantly increased in patients with ESRF, as compared to HC. Stratification analysis demonstrated that TS patients contained greater numbers of CD4⁺CD25⁺Foxp3⁺ and CD4⁺CXCR5⁺Foxp3⁺ T cells, higher levels of serum IL-10, and fewer numbers of CD4⁺CD25^-Foxp3⁺ T cells than ESRF patients. In contrast, ALR and AR patients contained fewer numbers of CD4⁺CD25⁺Foxp3⁺ and CD4⁺CXCR5⁺Foxp3⁺ T cells, greater numbers of CD4⁺CD25^-Foxp3⁺ T cells, and lower levels of serum IL-10 than ESRF patients. In TS patients, the numbers of CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25^-Foxp3⁺ T cells were positively correlated with eGFR and serum Cr levels, respectively.

Conclusion: An imbalance of different types of CD4⁺Foxp3⁺ T cells might be involved in renal transplant rejection.     

Immune Reconstitution following Myeloablative Allogeneic Hematopoietic Stem Cell Transplantation: The Impact of Expanding CD28negative CD8+ T Cells on Relapse

Allogeneic stem cell transplantation has become standard therapy for hematologic malignancies through the positive immunologic graft-versus-leukemia effect. Initial immune recovery relies on peripheral expansion of infused T cells, which switch to a memory-like phenotype. This study prospectively investigated whether changes in subset composition precedes complications after myeloablative HLA-matched transplantation for hematologic malignancies. Of 80 allograft recipients, 18 were still free of clinical complication throughout 395 to 1564 days of follow-up. Compared with this complication-free subgroup, patients who developed chronic graft-versus-host disease (cGVHD) without relapsing recovered similar numbers of circulating T cells with predominance of CD8⁺ T cells lacking CC-chemokine receptor-7 and CD28 expression throughout the first year after transplantation. Conversely, poor CD8⁺ T cell recovery with diminished numbers of CD28^neg CD8⁺ T cells (∼1/4th of that of relapse-free patients) preceded occurrence of malignant relapse. In multivariate analysis, lower CD28^neg CD8⁺ T cell counts by day 60 postallograft were associated with a greater risk of subsequent relapse (hazard ratio [HR] 0.33; 95% confidence interval [CI]: 0.14-0.76; P = .01). Enumeration of CD28^neg CD8⁺ T cells in patients could assist in predicting risk of relapse and help build an algorithm for accelerating the immune recovery by reducing the immunosuppressive treatment and considering the introduction of preemptive donor lymphocyte infusions.     

Immunosenescence increases the rate of acceptance of kidney allotransplants in elderly recipients through exhaustion of CD4 T-cells

Compromised immunity is the hallmark of ageing. Paradoxically, it may be “an ally” in facilitating acceptance of allogeneic grafts in the elderly. In this retrospective study we looked for biomarkers of immunosenescence that distinguish elderly recipients less prone to reject kidney allografts.Recruited kidney recipients aged ≥60 or <60 were designated ‘elderly’ and ‘young’, respectively. Both age-groups were divided according to the history of acute rejection. The phenotype, length of telomeres, expression of FoxP3 and proliferative responses were assessed in CD4⁺ and CD8⁺ T-cell subsets. In addition, IL6, IL10 and TGFβ were measured on the level of mRNA and serum protein.Acute-rejection-free history in elderly transplant recipients was associated with short telomeres, a decreased proportion of CD28⁺ T-cells associated with CMV-seropositivity and low proliferation of CD4⁺ T-cells. In contrast, elderly recipients who experienced acute rejection kept preserved telomere length, had a higher number of functional CD4⁺CD28⁺ cells and exhibited vigorous proliferation in vitro. These differences were not found in the young group.The major conclusion of this study is that the impaired condition of CD4⁺ T-cells, so-called immunosenescence, renders transplant recipients less responsive to an allogeneic kidney graft, an effect that was limited to transplant recipients of >60 years of age.     

Flexibility of the Thyroiditogenic T Cell Repertoire for Murine Autoimmune Thyroiditis in CD8-Deficient (B2m -/-) and T Cell Receptor VBC Congenic Mice

In murine experimental autoimmune thyroiditis (EAT), previous studies have revealed a highly adaptable thyroiditogenic T cell repertoire which involves both CD4⁺ and CD8⁺ T cells in the susceptible H2k strain. To further test this flexibility, congenic B10.K mice lacking CD8⁺ T cells (B2m -/-) or harboring 70% T cell receptor (TCR) V6 gene deletions (V6^C) were immunized with mouse thyroglobulin (MTg) and evaluated for EAT 28 days later. All 62m -/- mice developed moderate antibodies to MTg, and thyroidal inflammation was comparable to B10.K mice, averaging 35-40%. Spleen cells (SC) from MTg-immunized mice were then injected into syngeneic recipients after stimulation in vitro with MTg or with conserved, thyroxine (T4)- or thyronine (TO)- containing 12mer peptides, hT4(5), hT0(2553), or hT4(2553), derived from the primary hormonogenic sites at position 5 or 2553 of human Tg. As previously shown in another H2^k strain (CBA/J), all three peptides activated MTg-primed SC to transfer EAT in B10.K mice. hT4(5) and hT4(2553) were further tested in B10.K-V6^C and ß2m^- B10.K mice. Both peptides expanded thyroiditogenic T cells in either strain, resulting in severe thyroiditis in syngeneic recipients. That EAT can develop in the absence of CD8⁺ T cells or in the presence of a severely restricted TCR repertoire underscores the remarkable flexibility of the thyroiditogenic T cell profile in the susceptible k haplotype.     

Regulatory T cells generated during cytomegalovirus in vitro stimulation of mononuclear cells from HIV-infected individuals on HAART correlate with decreased lymphocyte proliferation

HIV-infected patients fail to fully recover cell-mediated immunity despite HAART. To identify regulatory factors, we studied the phenotype and function of in vitro cytomegalovirus (CMV)-stimulated T cells from HAART recipients. CFSE-measured proliferation showed CD4⁺ and CD8⁺ cells dividing in CMV-stimulated cultures. Compared with healthy controls, CMV-stimulated lymphocytes from HAART recipients had lower ³H-thymidine incorporation; lower IFNγ and TNFα production; higher CD4⁺CD27⁻CD28⁻ and CD8⁺CD27⁻CD28⁻ frequencies; lower CD4⁺CD25^hi; and higher FoxP3 expression in CD8⁺CD25^hi cells. CMV-specific proliferation correlated with higher IFNγ, TNFα and IL10 levels and higher CD4⁺perforin⁺ and CD8⁺perforin⁺ frequencies. Decreased proliferation correlated with higher CD4⁺CD27⁻CD28⁻ frequencies and TGFβ1 production, which also correlated with each other. Anti-TGFβ1 neutralizing antibodies restored CMV-specific proliferation in a dose-dependent fashion. In HIV-infected subjects, decreased proliferation correlated with higher CMV-stimulated CD8⁺CD25^hi frequencies and their FoxP3 expression. These data indicate that FoxP3- and TGFβ1-expressing regulatory T cells contribute to decreased immunity in HAART recipients.     

γδ T Cell Receptor Deficiency Attenuated Cardiac Allograft Vasculopathy and Promoted Regulatory T cell Expansion

γδ T cell comprises about 5% of the overall T cell population, and they differ from conventional αβ T cells. Previous studies have indicated the contribution of γδ T cell to acute allograft rejection, but the role of γδ T cell in cardiac allograft vasculopathy (CAV) is not investigated. Hearts of adult B6.C‐H‐2^bm12KhEg were heterotopically transplanted into major histocompatibility complex (MHC) class II‐mismatched C57BL/6 mice (wild‐type, γδ TCR^?/?), which is an established murine model of chronic allograft rejection without immunosuppression. The survival of grafts was monitored daily by abdominal palpation until the complete cessation of cardiac contractility. Our current study demonstrated that γδ T cell receptor (TCR) deficiency significantly attenuated CAV, and this effect coincides with low expression of Hmgb1, IFN‐γ and IL‐17 while increased number of CD4⁺CD25⁺Foxp3⁺ regulatory T cells, and depletion of regulatory T cells abrogated the prolonged allograft survival induced by γδ TCR deficiency. γδ TCR deficiency resulted in attenuated CAV and prolonged graft survival in murine models of cardiac transplantation, and this effect was associated with enhanced expansion of regulatory T cells.