细胞毒性T淋巴细胞相关抗原4诱导新鲜异体骨移植免疫耐受的实验研究

目的　利用外源性细胞毒性T淋巴细胞相关抗原4 ( cytotoxic T lymphocyte- associated antigen 4immuno globlin,CTL A4 - Ig)阻断T细胞反应的第2信号,诱导新鲜同种异体骨移植免疫耐受。　方法　采用近交系小鼠BAL B/C 6 6只作为骨移植的受体,进行异位肌袋一次及第2次骨移植。一次移植分为3组,每组18只,一组移植C5 7BL/6小鼠骨骼,注射L6 (对照品) ,为AL组;一组移植C5 7BL/6小鼠骨骼,注射CTL A4 - Ig,为AC组;一组移植同系BAL B/C小鼠骨骼,注射PBS缓冲液,为AB组。在第2、4及6周,进行血淋巴细胞亚群分析,血清抗体测定,供体细胞及抗原二次刺激实验及组织学观察。另取12只BAL B/C小鼠,进行第2次移植实验,供体为C5 7BL/6小鼠的骨骼,注射CTL A4 - Ig后2周,分别移植C5 7BL/6 ( BC组)和C3H( BH组)小鼠的骨骼,检测产生免疫耐受的特异性。　结果　AL组与AB组比较,产生了强烈的免疫排斥反应,移植后2、4及6周,CD4 T细胞的增殖明显增加( P<0 .0 5 ) ,血清抗体明显增多( P<0 .0 5 ) ,供体细胞及骨抗原二次刺激的细胞增殖也明显增加( P<0 .0 5 ) ;AC组免疫排斥反应较轻,在CD4 T细胞的增殖、血清抗体及二次刺激的细胞增殖方面均与AB组相似( P>0 .0 5 ) ;组织学观察也显示,异体骨周围的淋巴细胞浸润消失,软骨诱导及新骨形     

Critical role of proinflammatory cytokine IL-6 in allograft rejection and tolerance

The proinflammatory cytokine IL-6 plays an important role in controlling T-cell differentiation, especially the development of Th17 and regulatory T cells. To determine the function of IL-6 in regulating allograft rejection and tolerance, BALB/c cardiac grafts were transplanted into wild-type or IL-6-deficient C57BL/6 mice. We observed that production of IL-6 and IFN-γ was upregulated during allograft rejection in untreated wild-type mice. In IL-6-deficient mice, IFN-γ production was greater than that observed in wild-type controls, suggesting that IL-6 production affects Th1/Th2 balance during allograft rejection. CD28-B7 blockade by CTLA4-Ig inhibited IFN-γ production in C57BL/6 recipients, but had no effect on the production of IL-6. Although wild-type C57BL/6 recipients treated with CTLA4-Ig rejected fully MHC-mismatched BALB/c heart transplants, treatment of IL-6-deficient mice with CTLA4-Ig resulted in graft acceptance. Allograft acceptance appeared to result from the combined effect of costimulatory molecule blockade and IL-6-deficiency, which limited the differentiation of effector cells and promoted the migration of regulatory T cells into the grafts. These data suggest that the blockade of IL-6, or its signaling pathway, when combined with strategies that inhibit Th1 responses, has a synergistic effect on the promotion of allograft acceptance. Thus, targeting the effects of IL-6 production may represent an important part of costimulation blockade-based strategies to promote allograft acceptance and tolerance.     

CTLA4-Ig和IL-4诱导异种骨移植免疫耐受的体外研究

目的探讨CTLA4Ig和IL4在诱导异种骨移植免疫耐受中的作用。方法反应细胞为BALB/c小鼠脾淋巴细胞,刺激细胞为新西兰白兔血淋巴细胞,刺激抗原为兔骨上清液。采用经典的混合淋巴细胞培养法及骨上清液与淋巴细胞混合培养法作为异种骨移植的体外实验模型。在各培养液中分别加入CTLA4Ig、IL4及两者联合应用,通过测定其3HTdR掺入率,观察不同细胞因子对刺激淋巴细胞增殖的影响。结果1细胞刺激组CTLA4Ig和IL4均对淋巴细胞增殖有显著抑制作用P<0.001),CTLA4Ig与IL4联合应用并未显示出比CTLA4Ig单独应用更为明显的细胞增殖抑制作用(P>0.05)。2骨上清液刺激组:CTLA4Ig对细胞增殖无抑制作用(P>0.05),而IL4则有较为显著地细胞增殖抑制作用(P<0.05);CTLA4Ig与IL4联合应用也未产生比单独应用IL4更为明显的细胞增殖抑制作用(P>0.05)。结论CTLA4Ig对由细胞刺激产生的淋巴细胞增殖抑制效果较好,而IL4则对骨上清液刺激的细胞增殖抑制作用更好;CTLA4Ig与IL4联合应用并未产生协同抑制作用。     

小鼠异体皮移植创面使用细胞毒性T淋巴细胞抗原4-Ig重组腺病毒载体对其免疫功能的影响

目的　在小鼠背部移植异体皮后局部使用细胞毒性T淋巴细胞抗原 4 Ig(CTLA4 Ig)重组腺病毒载体 ,观察其对机体免疫功能的影响。　方法　将 6 0只BALB/c小鼠随机分为手术对照(A)组、CTLA4 Ig转染 (B)组及正常对照 (C)组 ,每组 2 0只。A、B组小鼠制作 1 .5cm× 1.5cm创面 ,移植同创面大小的C57BL小鼠皮肤后 ,A组小鼠创面涂抹不含腺病毒的交联聚丙烯酸树脂 (卡波姆霜 )0 .1g;B组小鼠创面涂抹含腺病毒的卡波姆霜 0 .1g,病毒滴度 5× 1 0 9/L。C组小鼠不作任何处理。术后 1d分别向 3组小鼠腹腔内注射体积分数 1 0 %绵羊红细胞 (SRBC)1ml。术后 7、1 4、2 1、2 8d收集血清进行凝集试验 ,检测SRBC抗体的效价 ,同时取BALB/c、C57BL及昆明小鼠的脾淋巴细胞作混合淋巴细胞培养 (MLC),观察CTLA4 Ig对脾淋巴细胞的抗原识别特异性及再次应答的影响。结果3组小鼠抗SRBC抗体效价组间比较 ,差异无显著性意义 (P >0.0 5 )。术后 1 4d内与A组比较 ,B组小鼠脾淋巴细胞与对C57BL小鼠脾淋巴细胞表现出特异性低反应 (P <0.0 5);1 4d后 ,A、B组的再次应答达到或超过C组 (P >0.0 5 )。结论　局部使用CTLA4 Ig重组腺病毒不影响小鼠的体液免疫功能 ,但可能引起系统性的特异性细胞免疫耐受。     

阻断第二信号诱导骨移植后对淋巴细胞亚群的抑制作用

目的　研究细胞毒性T淋巴细胞相关抗原(CTLA4Ig)对新鲜同种异体骨移植后血淋巴细胞亚群的影响。方法　在组织相容性抗原完全不同的两组小鼠间进行异位骨移植,于移植后第0、1天,腹腔注射CTLA4Ig100μg,分别于术后2、4、6周取受体外周血,利用流式细胞仪技术测定血淋巴细胞亚群CD     

Role of the CTLA4 pathway in hyporesponsiveness induced by intratracheal delivery of alloantigen

BACKGROUND: The authors previously reported that intratracheal delivery (ITD) of donor alloantigen induced donor-specific hyporesponsiveness to C57BL/10 cardiac allografts in CBA recipients and that blockade of the B7 pathways abrogated that hyporesponsiveness. In this study, the authors used a CD28-deficient model to evaluate which signal, either through CD28 or cytotoxic T-lymphocyte-associated antigen (CTLA4), is involved in the induction of hyporesponsiveness. METHODS: Seven days before transplantation of hearts from C3H/HeJ (H2k) mice into C57BL/6 (H2b) or CD28-deficient (C57BL/6 background) mice, the transplant recipients were given ITD of donor splenocytes (1 x 10(7)), alone or in combination with human CTLA4-immunoglobulin (Ig) (200 microg). RESULTS: ITD of C3H splenocytes induced donor-specific hyporesponsiveness to C3H cardiac grafts in C57BL/6 recipients (graft median survival time [MST], 40 days). Administration of CTLA4-Ig concurrently with ITD abrogated the prolonged allograft survival (MST, 12 days). Interestingly, ITD of C3H splenocytes induced prolonged survival of C3H allografts in CD28-deficient recipients (MST, 55 days). Furthermore, administration of CTLA4-Ig combined with ITD of C3H splenocytes abrogated the prolonged survival of C3H allografts in CD28-deficient recipients (MST, 7 days), whereas recipients given isotype-control antibody in combination with ITD of splenocytes had prolonged survival of C3H allografts (MST, 58 days). CONCLUSIONS: Taken together, the authors' findings indicate that a signal through CTLA4, rather than through CD28, plays an important role in the induction of hyporesponsiveness by ITD of alloantigen in this model.     

CTLA4-Ig-modified dendritic cells inhibit lymphocyte-mediated alloimmune responses and prolong the islet graft survival in mice

The induction of antigen specific tolerance is critical for prevention and treatment of allograft rejection. In this study, we transfected CTLA4-Ig gene into dendritic cells (DCs), and investigated their effect on inhibition of lymphocyte activity in vitro and induction of immune tolerance on pancreatic islet allograft in mice. An IDDM C57BL/6 murine model induced by streptozotocin is as model mouse. The model mice were transplanted of the islet cells isolated from the BALB/c mice to their kidney capsules, and injected of CTLA4-Ig modified DCs (mDCs). The results showed that mDCs could significantly inhibit T lymphocyte proliferation and induce its apoptosis; whereas, unmodified DCs (umDCs) promoted the murine lymphocyte proliferation. Compared with injection of umDCs and IgG1 modified DCs, the injection of mDCs prolonged IDDM mice's allograft survival, and normalized their plasma glucose (PG) levels within 3 days and maintained over 2 weeks. The level of IFN-gamma was lower and the level of IL-4 was higher in mDCs treated recipient mice than that in control mice, it indicated that mDCs led to Th1/Th2 deviation. After 7 days of islet transplantation, HE stain of the renal specimens showed that the islets and kidneys were intact in structure, and islet cells numbers are increased in mDCs treated mice. Our studies suggest that DCs expressing CTLA4-Ig fusion protein can induce the immune tolerance to islet graft and prolong the allograft survival through the inhibition of T cell proliferation in allogeneic mice.     

Effect of CTLA4-Ig on Obliterative Bronchiolitis in a Mouse Intrapulmonary Tracheal Transplantation Model

Objectives: One of the serious problems after lung transplantation is chronic lung allograft dysfunction (CLAD). Most CLAD patients pathologically characterized by obliterative bronchiolitis (OB). Cytotoxic T-lymphocyte-associated antigen 4 (CTLA4)-Ig is a combination protein of the Fc fragment of human IgG1 linked to the extracellular domain of CTLA4. The aim of the study was to examine the effect of CTLA4-Ig therapy on OB using a mouse intrapulmonary tracheal transplantation (IPTT) model.Methods: IPTT was performed between BALB/c (donor) and C57BL/6 (recipient) mice. Abatacept, which is a commercially available form of CTLA4-Ig, was intraperitoneally injected in recipient mice immediately after surgery, on days 7, 14, and 21. The mice in the control group received human IgG.Results: We performed semi-quantitative analysis of graft luminal obliteration at post-transplant day 28. We calculated the obliteration ratio of the lumen of the transplanted trachea in each case. The obliteration ratio was significantly lower in the CTLA4-Ig group than that in the control group (91.2 ± 2.1% vs. 47.8 ± 7.9%, p = 0.0008). Immunofluorescent staining revealed significantly decreased lymphoid neogenesis in the lung.Conclusions: CTLA4-Ig therapy attenuated tracheal obliteration with fibrous tissue in the mouse IPTT model. The attenuation of fibrous obliteration was correlated with the inhibition of lymphoid neogenesis.     

Long-Term Survival of Intestinal Allografts Induced by Costimulation Blockade, Busulfan and Donor Bone Marrow Infusion

Tolerance-inducing strategies that infuse donor bone marrow cells in conjunction with costimulation blockade have not been applied to intestinal transplantation. Intestines from BALB/c mice were transplanted into C57BL/6 recipients treated with anti-CD40L mAb, CTLA4-Ig, donor bone marrow, and busulfan. The majority of mice transplanted after completion of this regimen developed hematopoietic macrochimerism, although the degree of chimerism varied widely between recipients, and experienced long-term allograft survival. T cells from these mice demonstrated donor-specific hyporesponsiveness in vitro. However, T cells from chimeric mice proliferated to donor alloantigen in vivo. Furthermore, chimeric mice bearing intestinal allografts were capable of rejecting subsequently placed donor-strain skin grafts. These data suggest that although long-term allograft survival occurs in the absence of acute or chronic rejection, recipient mice are not completely unresponsive to donor alloantigens. When intestinal transplantation was performed at the time of initial bone marrow infusion (initiation of the chimerism protocol), most recipients failed to develop chimerism and promptly rejected the intestinal allograft. Although this is the most effective protocol that we have tested using this stringent model of transplantation, our observations suggest that modifications will be necessary before it can be reliably applied to the transplantation of highly immunogeneic organs like the intestine.     

Targeted gene disruption of the heat shock protein 72 gene (hsp70.1) in the donor tissue is associated with a prolonged rejection-free survival in the murine skin allograft model

It is known that the expression level of the heat shock protein (HSP) is elevated in allograft tissues, but the specific role of the HSP in the acute rejection has not been elucidated. This study aims to determine how and when the HSP72 molecule works immunologically in the process of acute allograft rejection from a skin graft model in which HSP72 (hsp70.1 gene) knock out (KO) mice were adopted either as a donor or as a recipient. In experiment I, tail skin was grafted from either the HSP72 KO C57BL/6 mice or wild-type C57BL/6 mice--as the allograft control--onto the trunk of B10BR mice. The grafts were observed for any signs of rejection until the 14th day after the graft. The survival of the grafted skin from the two donor groups was analyzed by a log-rank method. The grafted skin was observed for the degree of rejection using light microscopy. In addition, the degree of apoptosis was assessed using a terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). A mixed lymphocyte reaction (MLR) was observed with HSP72 KO C57BL/6 splenocytes as the stimulator and B10BR mice lymphocytes as the responder cells. The cytokine levels, such as interleukin-2 (IL-2) and interferon-gamma, were measured from an MLR supernatant using enzyme-linked immunosorbent assay (ELISA). In experiment II, the tail skin was grafted in the opposite direction from the B10BR mice to the HSP72 KO or wild-type C57BL/6 mice, and the grafts were observed for any signs of rejection, as defined in experiment I. The absence of HSP72 expression was observed in the HSP72 KO mice lymphocytes after heat stress (42 degrees C) using Western blot analysis. In experiment I, the survival of the skin grafts from the HSP72 KO C57BL/6 mice was 12+/-1.3 days (median+/-S.E.), which was significantly longer than that from the allograft control donor (9+/-0.6 days; p=0.03). This coincided with the microscopic finding of the graft tissues. The MLR response of the CD4+ lymphocytes stimulated by HSP72 KO C57BL/6 splenocytes was lower, and the interferon-gamma concentration from the MLR supernatant was also lower. On Day 9, 3.7+/-1.1(mean+/-S.D.) TUNEL-positive cells per unit high-power field (HPF) were observed from the HSP72 KO C57BL/6 skin, which was significantly lower than that from the control skin (8.7+/-2.1 cells/HPF; p=0.045). In contrast, in experiment II, there was no difference in the survival of the skin graft either from the B10BR to HSP72 KO C57BL/6 mice or from the B10BR to the wild-type C57BL/6 mice. In summary, the survival of the skin grafts from the HSP72 KO C57BL/6 mice was prolonged, and the degree of rejection was lower than that from the allograft control. This means that the presence of HSP72 in the donor tissue is related to the up-regulation of acute rejection from the recipient immune system. The HSP72 KO mice as the donor were shown to have decreased level of antigen presentation to the recipient CD4+ lymphocytes. Therefore, the HSP72 molecule from the donor cells is believed to be related to the induction of the recipient immune reaction via alloantigen presentation.     

Blockade of LIGHT/HVEM and B7/CD28 signaling facilitates long-term islet graft survival with development of allospecific tolerance

BACKGROUND: Previous studies have shown that blockade of LIGHT, a T-cell costimulatory molecule belonging to the tumor necrosis factor (TNF) superfamily, by soluble lymphotoxin beta receptor-Ig (LTbetaR-Ig) inhibited the development of graft-versus-host disease. The cardiac allografts were significantly prolonged in LIGHT deficient mice. No data are yet available regarding the role of the LIGHT/HVEM pathway in more stringent fully allogeneic models such as skin and islet transplantation models. METHODS: Streptozotocin-induced chemical diabetic BALB/C mice underwent transplantation with allogeneic C57BL/6 islets and were treated with LTbetaR-Ig, CTLA4-Ig or a combination of both in the early peritransplant period. RESULTS: Administration of CTLA4-Ig or LTbeta R-Ig alone only increased graft survival to 55 days and 27 days respectively, whereas simultaneous blockade of both pathways significantly prolonged the islet allograft survival for more than 100 days. Long-term survivors were retransplanted with donor-specific (C57BL/6) islets and the grafted islets remained functional for more than 100 days. All of islet allografts were protected against rejection when the mixtures of 1x10(6) CD4+ T cells from tolerant mice and islet allografts were cotransplanted under the renal capsule of the na?ve BALB/c recipients. CONCLUSIONS: These data indicate that: 1) a synergistic effect for prolonged graft survival can be obtained by simultaneously blocking LIGHT and CD28 signaling in the stringent model of islet allotransplantation; 2) development of donor-specific immunological tolerance is associated with the presence of regulatory T-cell activity; and 3) local cotransplantation of the allografts with the regulatory T cells can effectively prevent allograft rejection and induce donor-specific tolerance in lymphocytes-sufficient recipients.     

Simultaneous inhibition of B7 and LFA-1 signaling prevents rejection of discordant neural xenografts in mice lacking CD40L

Abstract: Transplantation of embryonic human neural tissue can restore dopamine neurotransmission and improve neurological function in patients with Parkinson's disease. Logistical and ethical factors limit the availability of human embryonic allogeneic tissue. Embryonic xenogeneic neural tissue from porcine donors is an alternative form of donor tissue, but effective immunomodulatory techniques are warranted for neural xenotransplantation to become clinically feasible. We transplanted embryonic porcine ventral mesencephalic tissue into the brains of adult untreated C57BL/6 mice, untreated CD40L-/–mice and CD40L-/–mice that received injections of anti-LFA-1, CTLA4Ig or both compounds. Double-treated CD40L-/–mice had large grafts with high numbers of dopaminergic neurons 4 wk after transplantation. The grafts were completely devoid of lymphocytes, macrophages and activated microglia. Untreated C57BL/6 mice had rejected their grafts. Untreated CD40L-/–mice and CD40L-/–mice treated with monotherapy of anti-LFA-1 or CTLA4Ig had smaller grafts and more microglial and lymphocytic infiltration than double-treated CD40L-/–mice. We conclude that immunomodulation with concomitant inhibition of LFA-1 and B7 signaling in the perioperative period in CD40L-/–mice prevented the rejection of discordant neural xenografts. The treatment most likely reduced antigen presenting capacity and interfered with the costimulatory signaling needed for T cell activation to occur.     

Changes in expression of T-cell activation-related molecules and cytokines during tolerance induction in an allogeneic skin transplantation murine model

Bone marrow transplantation after treatment with busulfan and costimulatory blockade with monoclonal antibodies (mAb) cytotoxic T lymphocyte antigen 4 (CTLA4)-Ig and anti-CD154 mAb or two-signal blockade using anti-CD45RB and anti-CD154 mAb are nonmyeloablative treatment regimens for allogeneic transplantation. There may be differences in the mechanisms of donor cell engraftment and reactive cell deletion by which these regimens induce donor-specific tolerance. Therefore, this study was performed to investigate changes in T cells and cytokines during tolerance induction toward allogeneic skin grafts. BALB/c and C57BL/6 mice were used as donors and recipients, respectively. Skin and bone marrow transplantations were performed and busulfan was administered. Three groups were treated with mAb as follows: group 1, anti-CD154 mAb; group 2, anti-CD154 plus anti-CD45RB mAb; and group 3, anti-CD154 mAb plus CTLA4-Ig. The proportions of CD4+ or CD8+ T cells and the expression of CD45RB isoforms on splenocytes were measured using flow cytometry and the production of cytokines by CD4+ T cells using enzyme-linked immunosorbent assay. Group 2 showed a significant reduction in the proportions of CD8+ T cells and CD45RB high isoforms compared with groups 1 and 3. The levels of interleukin (IL)-2 and IL-4 in group 2 were lower and higher than those of groups 1 and 3, respectively. In conclusion, the combined use of anti-CD154 and anti-CD45RB mAb decreases the CD8+ T-cell population and the expression of CD45RB, resulting in a Th2 cytokine profile, which may be a characteristic mechanism leading to donor cell engraftment and reactive cell deletion for donor-specific tolerance.     

IL-4与IL-10联合诱导异种骨移植免疫耐受的体外研究

目的　探讨 IL - 4和 IL - 10在诱导异种骨移植免疫耐受中的作用。方法　反应细胞为 BAL B/c小鼠脾淋巴细胞 ,刺激细胞为新西兰白兔血淋巴细胞 ,刺激抗原为兔骨上清液。采用经典的混合淋巴细胞培养法及骨上清液与淋巴细胞混合培养法作为异种骨移植的体外实验模型。在各培养液中分别加入 IL - 4、IL - 10及两者联合应用 ,通过测定其 3H- Td R掺入率 ,观察不同细胞因子对刺激淋巴细胞增殖的影响。结果　无论在细胞刺激组还是骨上清液刺激组 ,IL- 4对淋巴细胞增殖均有显著抑制作用 (P<0 .0 0 1和 P<0 .0 5 ) ,IL- 10未表现出抑制作用 (P>0 .0 5 )。在两组 IL- 4和 IL - 10联合应用均产生比 IL - 4单独应用更为明显的细胞增殖抑制作用 (P<0 .0 0 1和 P<0 .0 5 )。结论　 IL - 4对由细胞或骨上清液刺激产生的淋巴细胞增殖均有很好的抑制作用 ,IL- 10没有表现出抑制作用 ;IL- 4与 IL- 10联合应用有协同抑制作用。     

Detecting rejection after mouse Islet transplantation utilizing islet protein-stimulated ELISPOT

Improved posttransplant monitoring and on-time detection of rejection could improve islet transplantation outcome. The present study explored the possibility of detecting harmful events after mouse islet transplantation measuring the immune responsiveness against islet extracts. Mouse islet transplantations were performed using various donor/recipient combinations, exploring autoimmune (NOD/SCID to NOD, n = 6) and alloimmune events (C57BL/6 to BALB/c, n = 20), a combination of both (C57BL/6 to NOD, n = 8), the absence of both (BALB/c to BALB/c, n = 21), or naive, nontransplanted control mice (n = 14). The immune reactivity was measured by ELISPOT, looking at the ex vivo release of IFN-γ from splenocytes stimulated by islet donor extracts (sonicated islets). The immune reactivity was not altered in the syngeneic and autoimmune models, demonstrating similar levels as nontransplanted controls (p = 0.46 and p = 0.6). Conversely, the occurrence of an allogeneic rejection alone or in combination to autoimmunity was associated to an increase in the level of immune reactivity (p = 0.023 and p = 0.003 vs. respective controls). The observed increase was transient and lost in the postrejection period or after treatment with CTLA4-Ig. Overall, allogeneic rejection was associated to a transient increase in the reactivity of splenocytes against islet proteins. Such a strategy has the potential to improve islet graft monitoring in human and should be further explored.     

Comparison of in vivo lymphocyte proliferation between allogeneic and xenogeneic heart transplantation in mice

There are controversial in vitro data comparing the strength of the cellular immune response between allogeneic and xenogeneic stimulator/responder combinations. The present study therefore compares in vivo lymphocyte proliferation using heart transplantation (HTx) models in mice. Heterotopic HTx into BALB/c mice was performed using donor organs from mice (BALB/c and C57BL/6) or Lewis rats. Intraperitoneally given bromodeoxyuridine (BrdU) was incorporated into the DNA and was subsequently analyzed by flow cytometry. On postoperative days 3 and 5, proliferation of splenocytes, CD4(+) T-lymphocytes, and CD19(+) B-lymphocytes was significantly higher after xenogeneic than after allogeneic and isogeneic HTx. No significant difference was observed when proliferation of CD8(+) lymphocytes was determined. The increased in vivo proliferation after xenotransplantation may reflect an earlier and probably stronger cellular immune response compared to allogeneic transplantation. The higher CD4(+) lymphocyte proliferation underscores the importance of this cell population in xenograft rejection.     

Antigen-specific T-regulatory cells can extend skin graft survival time in mice

This study investigated the effects of donor antigen-specific CD4(+)CD25(+) T-regulatory cells (Tregs) on skin allografts in mice. An allogeneic skin transplant model was established using donor C57BL/6 or DBA and recipient BALB/c mice. Recipients were divided into 4 groups: control group without intervention (CON; C57BL/6 to BALB/c), rapamycin gavage group (RAP; C57BL/6 to BALB/c), CD4(+)CD25(+) Tregs-treated group (TRE; C57BL/6 to BALB/c), in which recipients received transfusions of CD4(+)CD25(+) Tregs stimulated with C57BL/6-derived immature dendritic cells, and the third-party donor group (DBA; DBA to BALB/c) in which recipients received transfusions of BALB/c CD4(+)CD25(+) Tregs stimulated with C57BL/6-derived immature dendritic cells. Mean (SD) survival time of the skin allografts in the TRE group was 17.0 (3.4) days, significantly longer than in the other groups: CON, 6.9 (1.9) days; RAP, 10.3 (3.0) days; and DBA, 10.8 (3.6) days. The TRE group demonstrated a significantly greater expression of transforming growth factor-β and interleukin (IL)-10. Donor antigen-specific CD4(+)CD25(+) Tregs effectively extend skin allograft survival in mice.     

Effect of intrasplenic injection of allogeneic bone marrow cells on the survival of lethally X-irradiated mice

Radiation chimeras in mice were induced by intrasplenic injection of allogeneic bone marrow cells instead of intravenous injection. Interestingly, the survival time in X-irradiated BALB/c mice inoculated intrasplenically (i.s.) with bone marrow cells from C3H/He mice was markedly prolonged as compared with that in X-irradiated BALB/c mice inoculated i.v. with bone marrow cells from C3H/He mice. However, when C57BL/6 mice were used as donors, a significant difference between i.s. injection and i.v. injection has not been found in survival time at 60 days after X irradiation. On the contrary, when bone marrow cells from BALB/c or C57BL/6 mice were injected into X-irradiated C3H/He mice, i.s. injection gave longer survival days to recipients than did i.v. injection. Based on testing their chimerism, it was suggested that lymphoid cells of donor origin were predominantly identified in almost all BALB/c or C3H/He recipients which were inoculated i.s. with bone marrow cells from C57BL/6 mice. However, somewhat incomplete chimerism was observed when the C3H/He to BALB/c donor-recipient combination was used and vice versa.     

Reepithelialized orthotopic tracheal allografts expand memory cytotoxic T lymphocytes but show no evidence of chronic rejection

BACKGROUND: Acute rejection of mouse tracheal allografts is characterized by infiltration of the lamina propria with CD4+/CD8+ T cells that leads to the destruction of the epithelium and luminal obliteration. The donor epithelium is progressively replaced by recipient-derived epithelium. Once allograft reepithelialization has occurred, immunosuppression can be withdrawn without inciting acute rejection. We hypothesize that reepithelialization will also prevent chronic rejection of the trachea after withdrawal of immunosuppression. METHODS: BALB/c tracheal grafts were transplanted orthotopically into allogeneic C57BL/6 recipients. Allografted mice were nonimmunosuppressed for 10 or 100 days or immunosuppressed with cyclosporine A continuously for 50 days and then withdrawn from immunosuppression for an additional 50 days. In addition, grafts from this group were then heterotopically retransplanted into isogenic C57BL/6 or allogeneic BALB/c recipients to assess their immunogenicity. RESULTS: Cyclosporine A-treated mice showed no signs of chronic rejection or priming of cellular immunity as measured by proliferation and cytokine secretion in a mixed leukocyte reaction. However, there was a notable expansion of memory CD8+ T cells specific for donor major histocompatibility complex. When these tracheal allografts were retransplanted heterotopically into C57BL/6 or BALB/c, they demonstrated reduced responses toward BALB/c and primed responses toward C57BL/6, respectively. These results suggest that the grafts express a chimeric phenotype consisting of both BALB/c and C57BL/6 antigens. CONCLUSION: These observations suggest that long-term withdrawal of immunosuppression does not lead to chronic tracheal rejection even in the presence of alloantigen specific cytotoxic T-lymphocyte responses and that the reepithelialized grafts may contain donor elements that impact the generation of immunity.     

Transgenic anti-CD4 monoclonal antibody secretion by mouse segmental pancreas allografts promotes long term survival

To compare the effectiveness of transgenic and systemic monoclonal antibody therapy for pancreas transplantation, vascularised segmental pancreas allografts from wild-type or transgenic pancreatic tissue that secreted monoclonal anti-CD4 were placed in CBA recipients in which diabetes had been induced chemically by streptozotocin (STZ, non-autoimmune diabetes). In untreated CBA recipients, wild-type BALB/c or C57BL/6 bml pancreas transplants were rejected in a mean survival time (MST) of 27 and 30 days, respectively. BALB/c and C57BL/6 graft survival improved when recipients were given a short course of T cell depleting monoclonal anti-CD4 antibody, (GK 1.5, 2 mg total on days -1, 0, 1, 2 with grafting on day 0) with MST +/- S.D. of 71 +/- 29 and 44 +/- 36 days, respectively. Thus, transient depletion of CD4 was effective in delaying pancreas allograft rejection in these strain combinations. The use of C57BL/6 bml mice transgenic for a rat anti-CD4 antibody (GK5 mice) as pancreas donors provided allografts that secreted sufficient anti-CD4 antibody to cause CD4 T cell depletion in the recipients (CD4 cells decreased from 30 to < 5% of small lymphocytes). This degree of depletion was not sustained and the CD4 recovery inversely correlated with graft survival. Mice with > 20% CD4 cells in the splenic lymphocyte population 4 weeks post-transplant rejected their grafts (3 of 10 mice). However, in 7 of 10 mice CD4 cells remained low (< 15%) and allografts survived for > 80 days. The GK5 allografts survived significantly longer than those from non-transgenic bml controls (MST 83 +/- 32 days, compared with 30 days, P < 0.0005). This survival time was similar to that of BALB/c allografts in CBA recipients treated with a high dose of anti-CD4 antibody. Thus, transgenic secretion of anti-CD4 antibody by the pancreas allograft was very effective in prolonging its survival.