Mediation of skin allograft rejection in scid mice by CD4+ and CD8+ T cells.

We analyzed the role of CD4+ and CD8+ T cells in H-2-disparate skin allograft rejection in the mutant mouse strain C.B-17/Icr scid with severe combined immunodeficiency. On the day of skin allografting, scid mice were adoptively transferred with negatively selected CD4+ or CD8+ splenocytes from normal unsensitized C.B-17/Icr mice. These populations were obtained using a double-mAb--plus--complement elimination protocol using anti-CD4 or anti-CD8 mAb that resulted in no detectable CD4+ or CD8+ cells by FACS and negligible numbers of cytolytic T lymphocytes by limiting dilution analysis in anti-CD8 treated populations. Spleen cells were removed from grafted mice at the time of rejection and were tested in vitro for antidonor reactivity in several assays: mixed lymphocyte culture, cell-mediated lympholysis, and LDA for CTL and for IL-2-producing HTL. The presence of Thy 1.2+, CD4+, or CD8+ cells was determined by FACS. All control C.B-17 mice and scid mice adoptively transferred with nondepleted CD4+, and CD8+ cells rejected skin allografts with similar mean survival times (15.6 +/- 1.5, 18.8 +/- 3.4, 18.0 +/- 5.4, respectively), whereas control scid mice retain skin allografts indefinitely (all greater than 100 days). C.B-17 syngeneic grafts survived indefinitely in all groups. At the time of rejection, splenocytes from scid mice receiving CD4+ cells had negligible donor-specific cytotoxicity in CML and negligible numbers of CTL by LDA, but demonstrated a good proliferative response in MLC and IL-2-producing cells by LDA (frequency = 1/1764). There were no detectable CD8+ cells present by FACS analysis. Conversely, splenocytes from scid mice adoptively transferred with CD8+ cells had strong donor-specific cytotoxicity in CML (58.8% +/- 16.1%) and CTL by LDA (frequency = 1/3448), but no significant proliferation was detected in MLC. There were no detectable CD4+ cells by FACS, but there were small numbers of IL-2-producing cells by LDA (frequency = 1/10,204). These data demonstrate that CD4+ cells adoptively transferred into scid mice are capable of mediating skin allograft rejection in the absence of any detectable CD8+ cells or significant functional cytolytic activity. The adoptive transfer of CD8+ cells also results in skin allograft rejection in the absence of detectable CD4+ cells. The detection of small numbers of IL-2 secreting cells in these mice may indicate that CD(8+)-mediated allograft rejection in this model is dependent on IL-2-secreting CD8+ cells.     

The role of CD8+ and CD4+ cells in islet allograft rejection

The requirements of CD8+ and CD4+ cells for islet graft rejection in combinations with different histoincompatibilities were investigated by in vivo administration of anti-Lyt-2.2 (CD8) mAb, anti-L3T4 (CD4) mAb, or both to recipient mice. In B10.AQR----B10.A (H-2K-incompatible) and B10.A(5R)----B10.A (H-2K- and IA-incompatible) combinations, administration of either anti-Lyt-2.2 (CD8) or anti-L3T4 (CD4) mAb completely blocked islet graft rejection, indicating that neither CD8+ cells nor CD4+ cells alone were capable of mediating rejection, and that collaboration of CD8+ cells and CD4+ cells was necessary. On the other hand, in the BALB/c----B6 (H-2- and non-H-2-incompatible) combination, administration of anti-Lyt-2.2 (CD8) or anti-L3T4 (CD4) mAb resulted in rejection of most of the grafts, although survival was prolonged significantly, and administration of both anti-Lyt-2.2 (CD8) and anti-L3T4 (CD4) mAb together completely blocked rejection. These results suggested that either CD8+ or CD4+ cells were capable of mediating rejection, but that rejection was maximal in the presence of both T cell subsets. Immunohistochemical analyses showed marked depletion of CD8+ cells and CD4+ cells in grafted islets as well as spleens when anti-Lyt-2.2 (CD8) and anti-L3T4 (CD4) mAb, respectively, were injected.     

Renal allograft rejection in CD4+ T cell-reconstituted athymic nude rats. The origin of CD4+ and CD8+ graft-infiltrating cells

PVG-rnu/rnu nude rats reject a fully allogeneic DA renal allograft after the adoptive transfer of naive CD4+ T cells alone, but rejection is accompanied by the accumulation of many CD8+ leukocytes within the graft. In order to clearly establish the provenance of these CD8+ cells infiltrating rejecting kidney allografts, nude recipients (PVG-RT7a) were injected with CD4+ T cells from the PVG-RT7b congenic strain bearing an allotypic variant of the leukocyte-common antigen. Dual fluorescence and immunohistochemistry demonstrated that approximately 75% of the total infiltrate was host-derived; the donor-derived RT7b population was almost entirely (92-99%) CD4+, CD5+, CD3+, and alpha beta TCR+. At least 97% of the CD8+ cells were of nude origin. There was no evidence of donor-derived CD8+ cells or of a CD4+8+ double-staining population. Unexpectedly, nearly half of the alpha beta TCR+ cells from the grafts were of nude origin.     

Role of CD4+ and CD8+ T cells in early and late acute rejection of small bowel allograft

BACKGROUND/PURPOSE: Results of small bowel transplantation remain unsatisfactory because of severe immune rejection. The current study aims to elucidate the role of activation of CD4+ and CD8+ T cells in early and late acute rejection of small bowel allograft and, hence, provide the immunologic basis for developing new therapeutic strategies. METHODS: We used an MHC fully mismatched (DA to Lewis) heterotopic rat small bowel transplant model and a unique FK506-based immunosuppressive regimen, which suppresses early acute rejection but does not prevent late acute rejection. Flow cytometric analysis was used to quantitate the number of activated CD4+ and CD8+ T cells in graft and host mesenteric lymph nodes. RESULTS: The survival (mean +/- SD) of intestinal allograft was significantly prolonged, from 6.6 +/- 0.84 days for the untreated group to 40.7 +/- 14.1 days for the FK506-treated group. Activation of CD4+ cells was suppressed significantly in the FK506-treated group on postoperative day 7 compared with the untreated group (29.4% +/- 3.55% v 52.83% +/- 11.9%; P <.01). Activation of CD8+ cells was similarly suppressed (31.5 +/- 10.34% v 48.53 +/- 14.34%; P <.05). Interestingly, at late acute rejection, activated CD4+ and CD8+ T cells remained at almost the same low levels as those on postoperative day 7 in the FK506-treated group. The spleen to body weight ratio was significantly increased in the untreated group (0.53 +/- 0.07), and slightly increased in the FK treated group (0.27 +/- 0.07, on postoperative day 7; 0.24 +/- 0.07 at late acute rejection) compared with the syngeneic group (0.18 +/- 0.02). CONCLUSION: The activation of CD4+ and CD8+ T cells was suppressed effectively by early potent immunosuppressive treatment resulting in prolonged survival of intestinal allograft. At late acute rejection, the CD4+ and CD8+ T cells remained at low-level activation status, in contrast to the surge of CD4+ and CD8+ activation during early acute rejection. This suggests that persistent T cell activation even at low level is sufficient to cause the late acute rejection eventually. A therapeutic strategy targeting these cells is needed for long-term engraftment.     

Role of CD4+ and CD8+ T cells in murine skin and heart allograft rejection across different antigenic desparities

The factors that influence the relative contribution of the T cell subsets to allograft rejection remain unclear. We compared skin and heart rejection in CD4 Knockout (KO), and CD8 KO mice across full-, minor-, and class II histocompatibility antigen (HA) mismatches. Skin allografts were rejected by either CD4+ or CD8+ T cells alone at any degree of antigenic mismatch. However, either the absence of CD4+ cells or a lesser degree of HA mismatch resulted in prolongation of graft survival. In contrast, fully allogeneic heart grafts were accepted in CD4 KO recipients, and minor HA mismatched heart grafts were accepted by both CD4 KO and CD8 KO mice. Thus, the T cell subsets required for allograft rejection are determined by the immunogenicity of the tissue transplanted. In the absence of CD8+ T cells, perforin and Fas ligand (FasL) but not granzyme B mRNA were detected in rejecting grafts. Thus, granzyme B is a CD8+ cytotoxic T lymphocyte (CTL)-specific effector molecule.     

CD4+CD25+T细胞对同种异体小鼠心脏移植的免疫调节作用

目的 观察CD4+CD25+T细胞(Treg)对小鼠同种异体心脏移植的免疫调节作用.方法 流式细胞仪检测正常小鼠和胸腺切除+PC61小鼠淋巴结、脾脏和外周血的Treg的比例.将供体鼠BALB/C心脏移植到受体鼠B6腹腔内,观察对照组(n=6)、胸腺切除组(THY,n=8)、hCTLA4Ig组(n=8)、DST+hCTLA4Ig组(n=8)和THY+PC61+DST+hCTLA4Ig组(n=6)小鼠心脏移植后生存时间和移植心脏病理学检查.结果 正常B6小鼠淋巴结、脾脏和外周血的Treg的比例分别为5.1%、4.5%和1. 7%,明显高于胸腺切除+PC61处理组(1. 8%、1.7%、0.7%).移植心脏平均存活时间在对照组和胸腺切除组分别为(8.2±2.9)d和(7.6±3.0)d,两组间差异无统计学意义(P＞0.05);而在hCTLA4Ig组和DST+hCTLA4Ig组分别为(43.0±11.8)d和(135.0±29.7)d,均较对照组或胸腺切除组明显延长(P＜0.01);THY+PC61+DST+hCTLA4Ig组移植心脏平均存活时间(25.8±8.9)d,也明显较对照组明显延长,但短于hCTLA4Ig组和DST+hCTLA4Ig组(P＜0.01).DST+hCTLA4Ig组移植的心脏存活时间(135.0±29.7)d明显高于其他各组(P＜0.01),其病理组织学表现为间质内有较多的淋巴细胞浸润,伴毛细血管增生,管壁增厚,间质纤维化.结论 CD4+CD25+T细胞水平对同种异体心脏移植的免疫耐受具有免疫调节作用.

Abstract：

Objective To investigate the immunoregulation effects of CD4 + CD25 + T cells in mice heart allograft transplantation. Methods Flow cytometry was used to analyze the contents of CD4 + CD25 +T regulatory cells (Tregs) of the lymph nodes, spleen and blood in the normal mice group and the thymusectomy (THY) + PC61 group. BALB/C mice served as the donors and C57BL/6 (B6) mice as the recipients. Five groups were established, including control group ( n = 6 ), THY group ( n = 8 ), hCTLA4Ig group ( n = 8 ), DST ( donor-specific T-depleted spleen cells) + hCTLA4Ig group ( n = 8) and THY + PC61+ DST + hCTLA4Ig group (n = 6). The survival time after heart allograft transplantation was observed and pathological examination was done in different groups. Results In control group, the rate of Tregs in lymph nodes, spleen and blood was 5. 1%, 4. 5% and 1.7% respectively, which was significantly higher than in THY + PC61 group ( 1. 8% , 1. 7% and 0. 7% respectively). The average survival time of control and THY groups was 8. 2 ± 2.9 and 7.6 ± 3. 0 days respectively ( P ＞ 0. 05 ). The average survival time of hCTLA4Ig and DST + hCTLA4Ig groups was 43.0 ± 11.8 and 135.0 ± 29. 7 days respectively, which was significantly longer than in control group or THY group ( P ＜0. 01 ). The average survival time of THY +PC61 + DST + hCTLA4Ig group was 25.8 ± 8.9 days, which was significantly longer than in control group,but shorter than in hCTLA4Ig group or DST + hCTLA4Ig group ( P ＜ 0. 01 ). The survival time in DST +hCTLA4Ig group was 135.0 ± 29. 7 days, which was significantly longer than other groups ( P ＜ 0. 01 ).The pathological examination revealed that there were more lymphocytes infiltration and capillary vessel proliferation in the desmohemoblast in the transplanted heart of DST + hCTLA4Ig group. Conclusion CD4 +CD25 +T cells regulate the immune tolerance in the allograft transplantation.     

Apoptosis and allograft rejection in the absence of CD8+ T cells.

BACKGROUND: The requirement for cytotoxic T lymphocytes during allograft rejection is controversial. We previously demonstrated that CD8+ T cells are not necessary for allograft rejection or for the induction of apoptosis in rat small intestinal transplantation. In this study, we examined the mechanisms of apoptosis and rejection after liver transplantation in the absence of CD8+ T cells. METHODS: Either Lewis or dark agouti rat liver grafts were transplanted into Lewis recipients to create syngeneic and allogeneic combinations. CD8+ T cells were depleted in an additional allogeneic group by treatment with OX-8 mAb on day -1 and day 1 after liver transplant. RESULTS: Apoptosis and rejection were observed in both the CD8+ T cell-depleted allogeneic and allogeneic grafts by hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, and radiolabeled-annexin V in vivo imaging. Granzyme B and FasL were expressed in all allogeneic transplants, including those depleted of CD8+ T cells, indicating that a mononuclear cell other than a CD8+ T cell can be the source of these molecules during allograft rejection. Activation of the caspase cascade was detected in all rejecting allografts. Caspases 3, 8, and 9 were activated at similar significantly elevated levels in both allogeneic and CD8+ T cell-depleted liver grafts. CONCLUSION: These data indicate that in the absence of CD8+ T cells an alternative pathway, associated with granzyme B and FasL expression and activation of the caspase cascade, can mediate apoptosis and graft rejection.     

Differentiation of human alloreactive CD4+ and CD8+ T cells in vitro

BACKGROUND: Recent studies have revealed that, during viral infection, ordered phenotypic and functional changes occur in human antigen-specific T cells. We analyzed whether a similar differentiation program is induced after alloantigen stimulation in vitro. METHODS: Peripheral blood mononuclear cells and purified CD4(+)CD45RA+, CD4(+)CD45RO+, and CD8+ T cells from healthy individuals were labeled with 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester (CFSE). Cells were co-cultured with allogeneic irradiated cells. Flow cytometric analysis was performed on days 3, 5, and 7 of culture using surface CD45RA, CD27, CD28, CCR7, and intracellular perforin and granzyme B markers in relation to CFSE dilution. RESULTS: Based on the decrease in CFSE fluorescence, both CD4+ and CD8+ T cells showed an early and vigorous response to allogeneic stimulation. Loss of CD45RA expression and up-regulation of CD27 and CD28 costimulatory molecules was an early event occurring in the first generations of dividing cells. Differentiation at later stages of proliferation was characterized by loss of CCR7 homing receptor expression, more pronounced in CD4+ than in CD8+ T cells, indicating the decreased ability of these cells to traffic to secondary lymphoid organs. Production of the cytotoxic effector molecules perforin and granzyme B increased with the number of cell divisions. CONCLUSIONS: Our data thus show that short-term phenotypic and functional changes of alloreactive T cells follow the differentiation pattern seen in the early stages of an antiviral immune response.     

Increased thymocyte CD4+CD8+ cells and T-cell receptor beta gene rearrangements in thymoma

Epithelial cells in thymoma and thymic carcinoma may influence T-cell development in the tumor. In this study, we investigated the cell surface phenotype and T-cell receptor (TCR) gene rearrangement of thymocytes in thymic tumors. TCR rearrangement was observed in all cases of thymoma (A, AB, B1–2). A faint band in each digestion suggested the deletion between D1 to C1 or D1 to J2, and an additional rearrangement band with BamHI suggested the rearrangement between D1 to J1. High percentages of CD1+ cells and CD4+CD8+ (DP) cells were detected in all cases of thymoma (A, AB, B1–2). There are two kinds of cell surface phenotypes increased in populations of thymoma; one is increased DP cells and the other is a relatively low percentage of DP cells accompanied by a relatively high percentage of CD3+CD69+ cells. These findings suggest that thymocytes in thymoma are derived from immature T-cell expansion.     

Increased CD4+ CD25+ T regulatory cell activity in trauma patients depresses protective Th1 immunity

OBJECTIVES: We recently reported increased CD4 CD25 T regulatory (Treg) activity after burn injury in mice. This study sought to determine if Tregs mediate the reduction in TH1-type immunity after serious injury in man and if Treg function is altered by injury. METHODS: Peripheral blood was withdrawn from 19 consenting adult patients (35.1 +/- 16.3 years of age) with Injury Severity Scores (ISS) 36.6 +/- 13.9 on days 1 and 7 after trauma and from 5 healthy individuals. CD4 T cells were purified and sorted into Treg (CD25(high)) and Treg-depleted populations. After activation of cells with anti-CD3/CD28 antibody, production of the TH1-type cytokine IFNgamma, TH2-type cytokines (IL-4 and IL-5), and the inhibitory cytokine IL-10 was measured using cytometric bead arrays. Treg activity was measured by in vitro suppression of autologous CD4 T cell proliferation. RESULTS: All patients survived, 9 (47%) developed infection postinjury. IFNgamma production by patient CD4 T cells was decreased on day 1 and day 7, when compared with healthy controls. However, when Tregs were depleted from the CD4 T cells, the IFNgamma production increased to control levels. Tregs were the chief source of IL-4 and IL-5 as well as IL-10. Treg suppression of T cell proliferation increased significantly from day 1 to day 7 after injury. CONCLUSIONS: We demonstrate for the first time that human Tregs are increased in potency after severe injury. Most significantly, Tregs are important mediators of the suppression of T cell activation and the reduction in TH1 cytokine production found after injury.     

Roles of CD4+ and CD8+ T cells in discordant skin xenograft rejection

An essential role of murine CD4+ T cells in immune reactivity and skin graft rejection in discordant xenogeneic combinations have been reported. Our study was conducted to further clarify the roles of CD4+ and CD8+ T cells in discordant skin xenograft rejection, by using CD4 and CD8 knockout [C57BL/6 Cr Slc (B6; H-2b) background] mice. When human skins were grafted on CD8 knockout mice or B6 mice, both hosts rejected human skin grafts within 12 days after grafting. By contrast, survival of human skin grafts was significantly prolonged in CD4 knockout mice (mean survival times=19.3+/-(SD) 1.6 days; median 19 days). Fully allogeneic C3H/He Slc (H-2k) skin grafts were rejected within 14 days in CD4 knockout mice, suggesting that non-CD4+ T cells in CD4 knockout mice were immunocompetent for allograft rejection. In spleens of these recipient mice, CD8+ T cells seemed to be activated 10 days after human skin grafting. Immunohistological analysis revealed the infiltration of CD8+ T cells at the site of transplanted human skin on CD4 knockout mice. To further examine the role of CD8+ T cells in CD4 knockout mice, human skin grafting was performed on day 0 followed by administration of anti-CD8 monoclonal antibody on days 0, 5, and 14. The administration of anti-CD8 monoclonal antibodies caused the significant prolongation of human skin graft survival. These results indicate the following two conclusions: (1) CD4+ T cells have an essential role in rejecting discordant human skin xenografts rapidly and (2) however, CD8+ T cells also are capable of rejecting discordant human skin xenografts.     

Expression of CXCR6 on CD8+ T cells was up-regulated in allograft rejection

CXCL16/SR-PSOX is a novel transmembrane-type chemokine, which was also identified as a novel scavenger receptor for oxidized low density lipoprotein. Its receptor CXCR6 expresses on activated CD8⁺ T cells, type 1-polarized CD4⁺, and constitutively expresses on NKT cells. Moreover, it has been shown that CXCL16 accumulated activated CD8⁺ T cells to sites of inflammation. To date, the effect of CXCL16 (SR-PSOX)/CXCR6 on CD8⁺ T cells and its role in allograft rejection/acceptance are not well understood. In the current study, we show that rejected allografts showed higher expressions of CXCR6 and CXCL16. More importantly, expression of CXCR6 on CD8⁺ T cells was also up-regulated by rejection. However, the blockade of CXCL16(SR-PSOX)/CXCR6 interaction could not inhibit cytotoxic activity of CD8⁺ T cells, and therefore, could not prolong the cardiac graft survival time.