Inhibition of human antigen-specific T cell proliferation by anti-T blast sera

Two antisera, one raised against activated human T lymphoblasts and one raised against the human T cell line HPB-ALL, have the ability to inhibit antigen-induced T cell proliferation. Antiproliferative activity is absorbed by T blasts and HPB-ALL cells, but not by B lymphoblastoid cell lines, alpha-ethylisothiouronium bromide-treated sheep red blood cell (AET-SRBC) receptor-negative lymphoid cells, or the T cell lines MOLT-4 and HSB. The effects of these antisera do not require the presence of complement and are not attributable to toxicity during culture. The F(ab')2 fragment of anti-T blast antiserum is also active.     

Mediation of antigen-induced suppression of renal allograft rejection by a CD4 (W3/25+) T cell

The mechanism of induction of specific immunosuppression by preoperative donor-specific blood transfusion in the rodent remains unclear. In a previous study we demonstrated that a single LEW blood transfusion in a DA rat results in the generation of donor-specific suppressor cells in the lymph node and thoracic duct lymph, detectable both in vivo and in vitro 7 days after DST. In contrast, no such activity was found in the splenic compartment. In this study lymphoid cells were harvested from either untreated DA rats or DA rats transfused 7 days previously with LEW blood and purified by rosette depletion using appropriate monoclonal antibodies. The purified lymphocyte subpopulation from transfused rats, of splenic or TDL origin, was adoptively transferred into syngeneic, lightly irradiated (200 rads) DA rats, where the adoptive transfer of 4.25 x 10(7) T (OX12-negative) cells (98.9% pure) or 2.5 x 10(7) CD4 (i.e., W3/25-positive, OX8 and OX12-negative) cells (97.9% pure), both of TDL origin, resulted in the indefinite survival of a LEW kidney (median survival time [MST]greater than 100 days), but not a PVG kidney (MST = 11 days). In contrast lymphocytes of splenic origin, regardless of the phenotype, did not prolong graft survival. Thus we have phenotypically characterized a CD4 (W3/25+) T suppressor cell that is generated after a single DST and is detectable 7 days later in the TDL but not the splenic compartment. Although there was no significant difference in the lymphocyte subset composition of lymphoid organs from transfused and untreated hosts, as determined by flow cytometry, the mean channel fluorescence of the lymphocyte population markers of cells harvested from transfused animals was significantly less than that observed with untreated controls, a finding which remains unexplained.     

Mechanisms of regulatory T cell counter-regulation by innate immunity

One of the most significant advances in the field of immunology in the last decade is delineation of the pivotal role of regulatory T cells (Tregs) in the maintenance of self-tolerance. While Tregs are just now being applied therapeutically in early phase clinical trials, data gleaned from basic and translational studies to-date suggest enormous potential to intervene in human disease. Data from our work and the work of others suggest that the innate immune system plays an important role in the differentiation and function of Tregs, largely through the production of cytokines but also through expression of cell surface ligands. These molecules are expressed differentially depending on whether the stimulus includes trauma, ischemia/necrosis, and microbial infection, and have opposing effects on Tregs, in contrast to those associated with dendritic cell maturation and somatic cell apoptosis, which promote Treg differentiation and function. We refer to the former process as Treg counter-regulation. Since the transplantation procedure involves surgical trauma, organ ischemia, and exposure to environmental microbes, Treg counter-regulation represents a key area of intervention to improve strategies for promoting allograft tolerance.     

Inhibition of anti-skin allograft immunity induced by infusions with photoinactivated effector T lymphocytes--the congenic model

We have previously reported the capacity to produce donor-specific tolerance to alloantigens by intravenous exposure to pretreated antidonor T cells. The current study has refined this system by using congenic mice differing only at the H-2 major histocompatibility complex genetic loci. Twelve days after B10 mice received MHC-incompatible B10.D2 skin grafts, their splenocytes that included an expanded population of cells mediating rejection were treated with 100 ng/ml 8-methoxypsoralen (8-MOP) photoactivated by 1 J/cm2 of ultraviolet A prior to infusion into naive B10 recipients. Whereas 8-MOP itself is biologically inert, photoactivated 8-MOP crosslinks DNA by covalently binding to pyrimidine bases. Recipient B10 mice were tested for tolerance to B10.D2 alloantigens in mixed leukocyte culture (MLC), cytotoxicity (CTL), and to in vivo delayed type hypersensitivity assays and challenged with a fresh B10.D2 graft. In vivo, the DTH response of the pretreated B10 mice was specifically suppressed to the relevant alloantigen, correlating with retention of B10.D2 skin grafts for up to 22 days postengraftment without visual evidence of rejection, in comparison to control complete rejection of the skin graft in less than 12 days. In vitro, splenocytes from B10 recipients of pretreated syngeneic splenocytes containing large numbers of B10 anti-B10.D2 T cells proliferated less in MLC and generated lower cytotoxic T cell responses to B10.D2 alloantigens than did controls and suppressed the B10 MLC and CTL responses to B10.D2 alloantigen. These results reveal that, in a highly defined congenic transplantation system, infusions of photoinactivated effector cells resulted in selective inhibition of the in vivo responses that correlated with allograft rejection and permitted prolonged retention of histoincompatible skin grafts. This approach may have significant practical applicability for treatment of human disorders caused by aberrant T cells.     

Visualization of the in vivo generation of donor antigen-specific effector CD8+ T cells during mouse cardiac allograft rejection: in vivo effector CD8+ T cell generation during allograft rejection

BACKGROUND: An adoptive transfer system was used to study the fate of alloreactive CD8+ H-2Kb-specific TCR transgenic (DES+) T cells in vivo after transplantation. METHODS: A trace population of 2.0x10(6) CD8+DES+ T cells were adoptively transferred into syngeneic CBA.Ca (H-2k) mice 24 hr before transplantation of an H-2Kb+ or H-2Kb- cardiac allograft. RESULTS: H-2Kb specific T cells proliferated and produced interleukin-2 and interferon-gamma in response to H-2Kb+, but not H-2Kb- cardiac allografts. CD8+DES+ T cells that infiltrated the H-2Kb+ cardiac allografts developed a distinct cell surface and cytokine phenotype compared with the CD8+DES+ T cells that remained in the periphery. H-2Kb-specific graft infiltrating T cells (a) underwent a larger number of cell divisions (> =3), (b) increased in size, (c) up-regulated CD69, and (d) down-regulated CD62L. CONCLUSIONS: These results demonstrate that alloantigen-specific T cells can be monitored in vivo during the immune response to an allograft and that the fate of CD8+ T cells specific for the allogeneic class I molecules expressed by the graft is different between cells in the periphery and those that infiltrate the graft.     

Stimulation of T cell immunity by arginine enhances survival in peritonitis

T cell-mediated immunity may play a role in host responses to infection. Arginine is a known thymic and T cell stimulator which enhances host allogenic, mitogenic, and anti-tumor responses. We, therefore, examined the effect of arginine on the survival of rats with severe and lethal peritonitis induced by cecal ligation and double-needle puncture (CLP). In Experiment 1, arginine HCl (100 mg) was given bid by gavage starting immediately after CLP. In Experiment 2, the same dose of arginine was given by gavage bid for 3 days pre-CLP and continued thereafter. In Experiment 3, arginine was administered iv post-CLP (100 mg tid). Arginine had no effect on overall survival in Experiment 1. In Experiments 2 and 3, arginine therapy significantly increased survival at all times. A separate experiment was carried out to determine the reason for the differential response to arginine administered via gavage or iv post-CLP (Experiments 1 and 3). Nonseptic rats showed a 400% increase in plasma arginine 30 min after gavage with 100 mg arginine (P less than 0.001). No rise in plasma arginine was noted when arginine was administered by gavage post-CLP. The impaired intestinal absorption or markedly increased utilization of arginine in this septic model may explain why no improved survival was seen in Experiment 1. The mechanism for the improved survival with arginine therapy seen in Experiments 2 and 3 may be related to its known thymic and T cell immunostimulatory effects.     

转染肝癌总RNA的树突状细胞疫苗对肝癌的抑制作用及其机制

目的探讨转染肝癌细胞总RNA转染的树突状细胞(DC)疫苗抑制肝癌作用及其机制。方法采用粒/巨噬细胞集落刺激因子(GM-CSF)和白细胞介素(IL)-4联合培养6 d成小鼠骨髓来源不成熟DC(iDC),质脂体转染肝癌细胞系Hepa1-6 RNA入iDC,用LPS刺激后成为Hepal-6 RNA/DC疫苗,对照组为iDC组、LPS/DC组Saline组,以每只2×10~6个细胞腹腔注射免疫小鼠每周1次共3次,然后接种5×10~5 Hepal-6细胞,观察肿瘤生长情况、特异性CTL活性的测定以及抗体阻断实验。结果实验组Hepal-6 RNA/DC组肿瘤在第8周为(8．5±3．6)mm,而iDC组、LPS/ DC组、Saline对照组分别为(36．6±3．6)、(31．3±4．7)、(32．2±4．0)mm,与实验组比较差异均有统计学意义(P＜0．05)。实验组脾细胞对Hepal-6细胞有特异性杀伤效应,而对肺癌LLC细胞无杀伤活性。所诱导的抗肿瘤效应细胞包括CD~(8+)、CD~(4+)T淋巴细胞。结论肝癌细胞的总RNA转染的DC肿瘤疫苗能诱导CD~(8+)、CD~(4+)T细胞免疫,是较有临床应用前景的肝癌免疫治疗方法。     

Alloantigen-driven T cell death mediated by Fas ligand and tumor necrosis factor-alpha is not essential for the induction of allograft acceptance

BACKGROUND: Fas ligand (FasL)-Fas and tumor necrosis factor alpha (TNFalpha)-tumor necrosis factor receptor (TNFR) interactions regulate immune responses and contribute to self-tolerance by mediating antigen-driven T cell apoptosis. It is not known whether FasL and TNFalpha, expressed by the recipient's lymphoid or nonlymphoid cells, are essential for the apoptosis of alloreactive T lymphocytes and the induction of allograft acceptance. METHODS: We compared the survival of fully allogeneic vascularized cardiac allografts between wild-type (wt) and FasL-mutant (gld) recipient mice. In addition, we studied cardiac allograft survival in gld mice injected with TNFalpha-neutralizing antibody. Allograft acceptance (graft survival >100 days) was induced by treating the recipients with CTLA4Ig, a recombinant fusion protein that blocks B7-CD28 T cell costimulation. In vivo alloantigen-driven apoptosis of mature CD4+ and CD8+ T lymphocytes was analyzed in mice repeatedly stimulated with allogeneic splenocytes. RESULTS: We found that CTLA4Ig induces 100% long-term acceptance of cardiac allografts in wt and gld mice. Similarly, CTLA4Ig induced 100% allograft acceptance in gld recipients injected with TNFalpha-neutralizing antibody. In vivo alloantigen-driven apoptosis of mature CD4+ and CD8+ T cells was significantly reduced in gld mice and in wt mice treated with anti-TNFalpha antibody. However, neutralizing TNFalpha activity in gld mice failed to abrogate alloantigen-driven T cell apoptosis. CONCLUSIONS: These data indicate that: (1) FasL and TNFalpha expression are not obligatory for the induction of long-term allograft acceptance by CTLA4Ig and (2) FasL- and TNFalpha-independent death pathways contribute to alloantigen-driven T cell apoptosis.     

The roles of T cell subpopulations in allograft rejection

In principle, cell-mediated allograft rejection can be brought about by cytotoxic T cells or by a DTH-like reaction. The first part of this article reviews the relative importance of these two mechanisms in graft rejection and concludes that the bulk of evidence points to cytotoxic T cells as being of major importance. In the discussion an operational definition of DTH is adopted--namely a mechanism that mediates bystander killing and depends on the existence of a radiation-sensitive effector mechanism. The rejection of skin and organ allografts in mammals is T cell dependent and the demonstration that such rejection can occur in heavily-irradiated T cell reconstituted animals and in the absence of demonstrable bystander effects leads to the conclusion drawn. This is not to imply that concomitant DTH reactions may not augment the rejection process nor to deny the possibility that in special circumstances DTH reactions may play an essential part. In the second part of this article, the roles in graft rejection of CD4+ and CD8+ cytotoxic T cells are considered. The classical collaborative interaction between class II-restricted CD4+ cells that play an inductive role, and class I restricted CD8+ cells that differentiate into cytotoxic effector cells, seems to be unnecessary in some allograft responses. Thus, not only can CD4+ T cells differentiate into class II-restricted cytotoxic T cells but CD8+ T cells, at least in some class I MHC-incompatible strain combinations, can develop into mature effector cells without an inductive signal from CD4+ T cells. This autonomy seems to be limited to MHC incompatibilities so that CD8+ cells alone are unable to mediate the rejection of minor-H incompatible grafts. For these latter types of grafts, CD4+ T cells can bring about graft rejection if multiple minor-H determinants are present, but for weak minor-H responses the classical collaborative scheme is necessary.     

Distal radioulnar allograft reconstruction after giant cell tumor resection

Giant cell tumor of bone is considered to be a benign, locally aggressive lesion. When diagnosed early, it can be successfully treated with wide en bloc excision. No reports of complete distal radioulnar allograft reconstruction after en bloc excision of a distal ulnar lesion were found in the literature. We report a case of a distal ulnar giant cell tumor treated with wide en bloc excision and 2-stage allograft reconstruction and followed up for 40 months.     

Skin allograft rejection by L3/T4+ and Lyt-2+ T cell subsets

The L3/T4+ and Lyt-2+ T-cell subsets can be depleted from mice, using selected monoclonal antibodies in vivo, at different times during rejection of, or priming to, allogeneic skin grafts. Although L3/T4+ cells are sufficient to reject skin grafts in naive Lyt-2-depleted mice, we show that Lyt-2+ cells can become involved, after an initial delay, in intact mice. Furthermore, these Lyt-2+ cells are primed to dominate the accelerated rejection of a normal secondary response. Mice depleted of L3/T4+ cells cannot be primed in this way, suggesting that priming of Lyt-2+ cells is dependent on help from L3/T4+ cells. However, in mice depleted of Lyt-2+ cells, priming for rapid rejection can be achieved, presumably via the L3/T4+ population. This suggests that the rejection of skin allografts in a given situation reflects different contributions of multiple effector mechanisms.     

Impairment of recipient cytolytic activity attenuates allograft vasculopathy

We investigated the role of CD4+ and CD8+ T subsets as well as T cell cytolytic effector mechanisms in the aortic allograft model of allograft vasculopathy using CD4 and CD8 gene knockout mice (CD4(-/-), CD8(-/-)) and mice deficient in cytolytic effector pathways. Medial apoptosis at 2 weeks was reduced in CD8(-/-) mice and in mice where cytotoxic T cell activity was compromised. At 8 weeks, substantial medial damage was observed in wild-type (WT) and CD4(-/-) recipients but medial preservation was evident in CD8(-/-) mice and in mice with impaired cytotoxic T cell activity. The intima/media ratio, a comprehensive measure of allograft vasculopathy, was similar in WT and CD4(-/-) recipients but was significantly reduced in CD8(-/-) mice and mice with impaired cytotoxic T cell activity. These data indicate that CD8+ T cells contribute to the vascular remodeling that is characteristic of allograft vasculopathy. They also show that CD8+ T cells participate in allograft vasculopathy in the absence of CD4+ T cell help. We further demonstrated that WT mice exhibited robust allograft vasculopathy in the presence of cyclosporin A immunosuppression but that allograft vasculopathy was ablated in cyclosporin-treated CD8(-/-) mice. This supports the hypothesis that non-CD8+ T cell effector mechanisms are sensitive to calcineurin inhibitor therapy but that CD8+ T cell-mediated allograft vasculopathy is refractory to such treatment. Taken together, our data suggest that CD8+ T cells contribute to the induction of vascular remodeling in allograft vasculopathy and provide evidence that novel therapies which target CD8+ T cell effector function might be effective in mitigating AV in the clinical setting.     

CD4+CD25+调节性T细胞在肿瘤免疫中的作用研究

CD4+CD25+调节性T细胞(Treg)在自身免疫耐受、免疫自稳、肿瘤免疫中发挥着重要作用,它可以抑制自身抗原或者非自身抗原如肿瘤抗原引起的免疫反应.人们对Treg细胞的免疫抑制作用已进行了相关的研究和临床应用,最新研究表明其能够诱导肿瘤特异性抗原和局部的免疫反应.此综述将讨论Treg细胞的相关表面分子及其在肿瘤免疫...