Rejection of grafts without histocompatibility antigen disparity by TAP1-/- mice: a role for CD4+ T cells

We have previously shown that TAP1-/- mice reject heart and skin grafts lacking an H-2 disparity. TAP1-/- mice, which are deficient for MHC-I molecules, probably have a T-cell repertoire with distinct reactivity to these molecules. We speculated that this rejection could be mediated by CD4+ T cells reactive to H-2(b) class I molecules, or to class I-derived peptides presented by self-APC. This hypothesis was tested in the present work. Presensitization of TAP1-/- mice with H-2K(b) peptides accelerated the rejection of C57BL/6 (H-2(b)) skin grafts (MST 13 days, P <.0057), indicating that these peptides were able to mobilize effector T cells that participate in rejection. In addition, CD4 T-cell depletion before transplantation induced a significant delay in rejection (P <.0011), showing that CD4 T cells have a major role in the rejection process, though other cells may also contribute. In conclusion, these results support our hypothesis that H-2(b) molecules may be targeted in graft rejection without an H-2 disparity. The low expression of MHC-I molecules on TAP1-/- mice may determine the selection of a T-cell repertoire that is reactive to self-MHC-I molecules, a phenomenon that is probably beyond the control of peripheral regulatory mechanisms.     

转化生长因子-β1联合白细胞介素-2体外诱导非肥胖糖尿病小鼠调节性T细胞的产生

目的 体外诱导非肥胖糖尿病(NOD)小鼠CD4+ CD25+Foxp3+调节性T细胞(Treg)的产生并检测其免疫抑制功能.探讨外源性白细胞介素(IL)-2在诱导方案中的作用.方法 分选NOD小鼠童贞T细胞(Naive T),利用Anti-CD3、Anti-CD28刺激,同时给予转化生长因子-β1(TGF-β1)和白细胞介素-2(IL-2),共同培养5 d,收获诱导性Treg(iTreg),经流式细胞仪检测其表型.利用体外T细胞增殖体系,对比NOD小鼠天然Treg(nTreg),评价iTreg的免疫抑制能力.将诱导方案中的IL-2撤除以观察其作用.结果 TGF-B1联合IL-2能诱导NOD小鼠Naive T转化为iTreg,较对照组有统计学意义[(41.33±3.21)%比(8.00±3.00)%,P《0.05].iTreg可有效抑制T细胞增殖,其能力与nTreg的差异元统计学意义[(40.33±1.03)%比(38.33±3.06),P》0.05].外源性IL-2有利于iTreg的产生[(41.33±3.21)%比(15.00±1.00)%,P《0.05].结论 TGF-β1联合IL-2可在体外诱导Naive T转化为具有免疫抑制功能的Treg.     

CD4+ T cells are sufficient to elicit allograft rejection and major histocompatibility complex class I molecule is required to induce recurrent autoimmune diabetes after pancreas transplantation in mice

BACKGROUND: We characterized the role of T cell subsets and major histocompatibility complex molecules in allograft rejection and recurrence of autoimmune diabetes. METHODS: Adoptive cell transfer and vascularized segmental pancreas transplantation were performed in mice. RESULTS: In an alloimmune response model, transfer of nondiabetic CD4, but not CD8 T cells, elicited pancreas allograft rejection in streptozotocin (STZ)-induced diabetic NOD/scid mice. Pancreas allografts were acutely rejected in STZ-induced diabetic NOD/beta2m mice (confirmed the absence of major histocompatibility complex [MHC] class I and CD8 T cells) and permanently accepted in NOD/CIIT mice (confirmed the absence of MHC class II and CD4 T cells). The results suggest that rejection of pancreas allograft is CD4-dependent and MHC class I-independent. In the autoimmune diabetes model, whole spleen cells obtained from diabetic NOD mice induced autoimmune diabetes in NOD/scid and NOD/CIIT mice, but the onset of diabetes was delayed in NOD/beta2m mice. However, the purified diabetic T cells failed to elicit autoimmune diabetes in NOD/beta2m mice. NOD/scid and NOD/CIIT pancreas grafts were acutely destroyed whereas four of six NOD/beta2m pancreas grafts were permanently accepted in autoimmune diabetic NOD mice. CONCLUSION: CD4 T cells are sufficient for the induction of allograft rejection, and MHC class I molecule is required to induce recurrent autoimmune diabetes after pancreas transplantation in mice.     

Prolonged allograft survival in anti-CD4 antibody transgenic mice: lack of residual helper T cells compared with other CD4-deficient mice

BACKGROUND: Investigations of the role of CD4 T lymphocytes in allograft rejection and tolerance have relied on the use of mouse models with a deficiency in CD4 cells. However, in mice treated with depleting monoclonal antibody (mAb) and in MHC class II knockout (KO) mice, there are residual populations of CD4 cells. CD4 KO mice had increased CD4- CD8-TCRalphabeta+ helper T cells, and both strains of KO mice could reject skin allografts at the normal rate. In this study, transgenic mice with no peripheral CD4 cells were the recipients of skin and heart allografts. Results were compared with allograft survival in CD4 and MHC class II KO mice. METHODS: GK5 (C57BL/6 bml mice transgenic for a chimeric anti-CD4 antibody) had no peripheral CD4 cells. These mice, and CD4 and class II KO mice, received BALB/c or CBA skin or cardiac allografts. Some GK5 mice were treated with anti-CD8 mAb to investigate the role of CD8 cells in rejection. CD4 and CD8 cells were assessed by FACS and immunohistochemistry. RESULTS: BALB/c skin on GK5 mice had a mean survival time +/- SD of 24+/-6 days, compared with 9+/-2 days in wild-type mice. Anti-CD8 mAb prolonged this to 66+/-7 days. BALB/c skin survived 10+/-2 days on class II KO and 14+/-2 days on CD4 KO, both significantly less than the survival seen on GK5 recipients (P<0.001). BALB/c hearts survived >100 days in GK5 recipients and in wild-type recipients treated with anti-CD4 mAb at the time of grafting, in contrast to a mean survival time of 10+/-2 days in untreated wild-type mice. Immunohistochemistry revealed that long-term surviving heart allografts from the GK5 recipients had CD8 but no CD4 cellular infiltrate. These hearts showed evidence of transplant vasculopathy. CONCLUSIONS: The GK5 mice, with a complete absence of peripheral CD4 cells, provide the cleanest available model for investigating the role of CD4 lymphocytes in allograft rejection. Prolonged skin allograft survival in these mice compared with CD4 and MHC class II KO recipients was clearly the result of improved CD4 depletion. Nevertheless, skin allograft rejection, heart allograft infiltration, and vascular disease, mediated by CD8 cells, developed in the absence of peripheral CD4 T cells.     

Reconstitution of T and NK cells after haploidentical hematopoietic cell transplantation using αβ T cell–depleted grafts and the clinical implication of γδ T cells

To investigate reconstitution of T and NK cells after αβ T lymphocyte–depleted haploidentical hematopoietic cell transplantation (HHCT) and the clinical implications of γδ T cells, we analyzed 50 pediatric patients who received 55 HHCTs using αβ T cell–depleted grafts. The number of CD3+ T cells and CD8+ T cells recovered rapidly and reached donor levels at days 180 and 60, respectively. Recovery of NK cells was rapid, and the median of NK cells at day 14 was comparable to the donor level. At day 14, median percentage of γδ T lymphocytes was 70.5%. After day 14, the percentage of γδ T cells gradually decreased, while the percentage of αβ T cells gradually increased. Patients with a low percentage (≤21%) of γδ T cells at day 30 had significantly higher incidence of cytomegalovirus (CMV) reactivation compared to patients with a high percentage (>70%) of γδ T cells (P < .01). In patients with acute leukemia, patients with high percentage of γδ T cells at day 30 showed significantly higher relapse‐free survival compared to those with low percentage of γδ T cells (P = .02). Data suggest that early recovery of γδ T cells decreases the risk of CMV reactivation and leukemia relapse.     

Adoptive immunity in immune-deficient scid/scid mice. I. Differential requirements of naive and primed lymphocytes for CD4+ T cells during rejection of minor histocompatibility antigen-disparate skin grafts

Using a model system in which mature lymphocytes were adoptively transferred into immunodeficient C.B17-scid/scid recipients, the requirement for CD4+ T cells in rejection of previously healed-in multiple minor-H-antigen-disparate skin grafts was investigated. Depletion of functional CD4+ cells was accomplished by anti-CD4 antibody + complement treatment prior to adoptive transfer followed by chronic anti-CD4 serotherapy in vivo. Homozygous scid mice harboring nondepleted naive donor cells effectively rejected minor-H-antigen-disparate grafts, whereas scid/scid mice harboring CD4+ T-cell-depleted naive cells did not. Homozygous scid mice harboring minor-H-antigen-primed cells rejected the minor-H-antigen-disparate allografts regardless of whether or not the animals had received anti-CD4 treatment, although rejection by the mice receiving anti-CD4 treatment was retarded compared to mice not receiving anti-CD4 treatment. All the mice that received viable donor cells rejected minor + H-2 disparate allografts, demonstrating effective immunity in this case was not dependent upon the activity of CD4+ T cells. These data suggest that in responses against multiple minor-H-antigen-disparate tissue, primary allograft rejection is absolutely dependent upon CD4+ cells, and secondary allograft rejection is not. The implications of these findings in understanding interactions of T cell subsets in vivo and of the utility of using homozygous scid mice as recipients for exploring the function of transferred lymphoid cell populations are discussed.     

Chronic cardiac allograft rejection in a rat model disparate for one single class I MHC molecule is associated with indirect recognition by CD4(+) T cells

T-cell mediated immune responses play a critical role in chronic allograft dysfunction. The complex nature of allograft rejection, particularly with respect to the vast repertoire of alloantigens and their mode of recognition by T cells, presents a major challenge for the design of well-controlled studies into the immunobiology of chronic rejection. The purpose of this study was to develop a rat model with restricted antigenic specificity that develops chronic rejection without any immunologic manipulation to study the T-cell response. PVG.1U allogeneic hearts disparate for one single class I antigen, RT.1A(u), were transplanted into PVG.R8 rat recipients. Grafts from PVG.R8 were used as syngeneic controls. Chronic rejection was studied by histological analysis of the grafted hearts at various time points posttransplantation (20-100 days). Donor specific alloreactive response was studied in a mixed lymphocyte reaction assay. All allografts survived more than 90 days and showed extensive evidence of chronic rejection, which was characterized by interstitial fibrosis, vasculitis, and occlusive myointimal thickening. Chronic rejection was evident by day 20 and most extensive by day 100 posttransplantation. In marked contrast, syngeneic grafts remained free of chronic lesions. Lymphocytes harvested from graft recipients showed a more vigorous proliferative response to allogeneic splenocytes as compared with that of lymphocytes from nai;ve animals. The proliferative response was primarily mediated by CD4(+) T cells recognizing the RT1.A(a) molecule via the indirect pathway. A single class I disparity in this model generates chronic rejection associated with potent CD4(+) T-cell responses induced by the indirect recognition pathway. The use of this antigenically restricted model may facilitate the design of well-controlled studies for the characterization of immune mechanisms responsible for chronic rejection.     

T cells with low CD2 levels express reduced restriction factors and are preferentially infected in therapy naïve chronic HIV‐1 patients

Introduction : Restriction factors (RFs) suppress HIV‐1 in cell lines and primary cell models. Hence, RFs might be attractive targets for novel antiviral strategies, but their importance for virus control in vivo is controversial. Methods : We profiled the expression of RFs in primary blood‐derived mononuclear cells (PBMC) from therapy‐naïve HIV‐1 patients and quantified infection. Results : Overall, there was no correlation between individual RF expression and HIV‐1 status in total PBMC. However, we identified a T cell population with low levels of intracellular CD2 and reduced expression of SAMHD1, p21 and SerinC5. CD2^low T cells with reduced RF expression were markedly positive for HIV‐1 p24. In contrast, CD2+ T cells were less infected and expressed higher levels of RFs. CD2^low T cell infection correlated with viral loads and was associated with HIV‐1 disease progression. Conclusions : In untreated therapy naïve chronic HIV‐1 patients, RF expression in T cells is associated with CD2 expression and seems to influence viral loads. Our study suggests that RFs help to control HIV‐1 infection in certain T cells in vivo and supports the potential for RFs as promising targets for therapeutic intervention.     

Flt3L‐mobilized dendritic cells bearing H2‐Kbm1 apoptotic cells do not induce cross‐tolerance to CD8+ T cells across a class I MHC mismatched barrier

Tolerization of allogeneic CD8⁺ T cells is still a pending issue in the field of transplantation research to achieve long‐term survival. To test whether dendritic cells (DC) bearing allogeneic major histocompatibility complex (MHC) class I mismatched apoptotic cells could induce cross‐tolerance to alloreactive CD8⁺ T cells, the following experimental strategy was devised. Rag2/γ_c KO B6 mice were treated with Fms‐like tyrosine kinase 3 ligand (Flt3L)‐transduced B16 melanoma cells to drive a rapid expansion and mobilization of DC in vivo. Of all DC populations expanded, splenic CD11c⁺CD103⁺CD8α⁺ DC were selectively involved in the process of antigen clearance of X‐ray irradiated apoptotic thymocytes in vivo. Considering that CD11c⁺CD103⁺CD8α⁺ DC selectively take up apoptotic cells and that they are highly specialized in cross‐presenting antigen to CD8⁺ T cells, we investigated whether B6 mice adoptively transferred with Flt3L‐derived DC loaded with donor‐derived apoptotic thymocytes could induce tolerance to bm1 skin allografts. Our findings on host anti‐donor alloresponse, as revealed by skin allograft survival and cytotoxic T lymphocyte assays, indicated that the administration of syngeneic DC presenting K^bm1 donor‐derived allopeptides through the indirect pathway of antigen presentation was not sufficient to induce cross‐tolerance to alloreactive CD8⁺ T cells responding to bm1 alloantigens in a murine model of skin allograft transplantation across an MHC class I mismatched barrier.     

Rapamycin‐Conditioned Donor Dendritic Cells Differentiate CD4+CD25+Foxp3+ T Cells In Vitro with TGF‐β1 for Islet Transplantation

Dendritic cells (DCs) conditioned with the mammalian target of rapamycin (mTOR) inhibitor rapamycin have been previously shown to expand naturally existing regulatory T cells (nTregs). This work addresses whether rapamycin‐conditioned donor DCs could effectively induce CD4⁺CD25⁺Foxp3⁺ Tregs (iTregs) in cell cultures with alloantigen specificities, and whether such in vitro‐differentiated CD4⁺CD25⁺Foxp3⁺ iTregs could effectively control acute rejection in allogeneic islet transplantation. We found that donor BALB/c bone marrow‐derived DCs (BMDCs) pharmacologically modified by the mTOR inhibitor rapamycin had significantly enhanced ability to induce CD4⁺CD25⁺Foxp3⁺ iTregs of recipient origin (C57BL/6 (B6)) in vitro under Treg driving conditions compared to unmodified BMDCs. These in vitro‐induced CD4⁺CD25⁺Foxp3⁺ iTregs exerted donor‐specific suppression in vitro, and prolonged allogeneic islet graft survival in vivo in RAG^?/‐ hosts upon coadoptive transfer with T‐effector cells. The CD4⁺CD25⁺Foxp3⁺ iTregs expanded and preferentially maintained Foxp3 expression in the graft draining lymph nodes. Finally, the CD4⁺CD25⁺Foxp3⁺ iTregs were further able to induce endogenous naïve T cells to convert to CD4⁺CD25⁺Foxp3⁺ T cells. We conclude that rapamycin‐conditioned donor BMDCs can be exploited for efficient in vitro differentiation of donor antigen‐specific CD4⁺CD25⁺Foxp3⁺ iTregs. Such in vitro‐generated donor‐specific CD4⁺CD25⁺Foxp3⁺ iTregs are able to effectively control allogeneic islet graft rejection.