Specific inhibition of the graft-versus-host reaction in fetal or neonatal liver chimeras.

The fetal liver chimera system was used as a model to study the nature of transplantation tolerance in radiation chimeras. A permanent state of tolerance was induced in (C3H/eb times C57BL/6)F1 irradiated mice after reconstitution with parental C57BL/6 fetal or neonatal liver cells. It was found that although enough host hemopoietic cells were present in such chimeras to provide antigenic stimulation, subsequent inoculation of these chimeras with C57BL/6 immunocompetent cells syngeneic to liver donor cells specifically abolished their response against the host. In addition, cells obtained from liver chimeras after their challenge with C57BL cells were unable to produce a graft-versus-host response upon transfer to (C3H/eb times C57BL/6)F1 newborn mice. Transfer of serum of these mice could not prevent immune reactivity of syngeneic C57BL/6 cells neither in the graft-versus-host nor in the mixed lymphocyte culture assays. These observations are compatible with the hypothesis that suppressor cells may differentiate within the fetal liver, which specifically inhibits the immune reactivity of syngeneic cells, and thus leads to the establishment of tolerance.     

Spleen plays an important role in maintaining tolerance after removal of the vascularized heart graft

BACKGROUND: This study addresses the question of the mechanism for maintaining tolerance to donor alloantigen in the absence of antigen and the role of secondary lymphoid tissues. METHODS: Depleting anti-CD4 antibody administration in conjunction with allogeneic heart transplantation generates donor-specific operational tolerance. Primary C57BL/6 heart grafts were transplanted into the neck cavity of the anti-CD4 antibody pretreated C3H/He mice. At day 50, functioning heart grafts were removed from tolerant mice. At day 100, a secondary C57BL/6 or a third-party heart was transplanted into the abdomen. RESULTS: Anti-CD4 antibody therapy induced CD4CD25 regulatory T cells by 50 days after transplantation, as depleting anti-CD25 treatment in tolerant mice abrogated graft prolongation when spleen leukocytes were adoptively transferred to syngeneic mice. Tolerance was maintained by CD4CD25 regulatory T cells via a CTLA-4 signal at 100 days, even after removal of the primary graft at day 50. Administration of anti-CD25 antibody immediately after removal of the primary graft did not break tolerance, as five out of six second allografts transplanted at day 100 were accepted. Anti-CD25 antibody therapy in conjunction with splenectomy, but not thymectomy, immediately after removal of primary heart grafts at day 50 broke tolerance at day 100; all allografts were rejected. CONCLUSION: The spleen is important in maintaining CD4CD25 regulatory T cells after primary allograft removal.     

NOD congenic mice genetically protected from autoimmune diabetes remain resistant to transplantation tolerance induction

The loss of self-tolerance leading to autoimmune type 1 diabetes in the NOD mouse model involves at least 19 genetic loci. In addition to their genetic defects in self-tolerance, NOD mice resist peripheral transplantation tolerance induced by costimulation blockade using donor-specific transfusion and anti-CD154 antibody. Hypothesizing that these two abnormalities might be related, we investigated whether they could be uncoupled through a genetic approach. Diabetes-resistant NOD and C57BL/6 stocks congenic for various reciprocally introduced Idd loci were assessed for their ability to be tolerized. Surprisingly, in NOD congenic mice that are almost completely protected from diabetes, costimulation blockade failed to prolong skin allograft survival. In reciprocal C57BL/6 congenic mice with NOD-derived Idd loci, skin allograft survival was readily prolonged by costimulation blockade. These data indicate that single or multiple combinations of evaluated Idd loci that dramatically reduce diabetes frequency do not correct resistance to peripheral transplantation tolerance induced by costimulation blockade. We suggest that mechanisms controlling autoimmunity and transplantation tolerance in NOD mice are not completely overlapping and are potentially distinct, or that the genetic threshold for normalizing the transplantation tolerance defect is higher than that for preventing autoimmune diabetes.     

Neutralization of immunosuppression by antibodies against variable as well as constant regions of monoclonal anti-Thy-1 xenoantibodies and their ability to be suppressed by initial T cell depletion

Timing, magnitude, and effect of the murine antibody response to rat pan-T-cell antibodies were studied in a bone marrow (C57BL/6-to-CBA mice) transplantation model. Prospective C57BL/6 marrow donor mice were sensitized against pan-T-cell (Thy-1, Thy-1.2, Lyt-1) monoclonal antibodies of various rat isotypes or against polyclonal rat antimouse-thymocytes (rat ATG) antibodies. Three days prior to transfer of spleen and bone marrow cells, the sensitized C57BL/6 donors received a dose of anti-Thy-1 mAb (RmT1) known to abolish graft-versus-host reactivity of unsensitized donors. The injected mAb provoked anti-antibodies reacting with RmT1. The anti-antibodies inhibited immunosuppression of the rat mAb RmT1 even if they bound only to nonidiotypic epitopes on RmT1. Avoiding cell-binding of the sensitizing rat anti-Thy-1.2 mAb by its injection into Thy-1.1 mice induced only low-titer and delayed anti-antibodies. This indicated the enhanced immunization potential of anti-Thy-1 when bound to cells. Finally, sensitization leading to the mouse antirat anti-antibodies and reversion of immunosuppression was prevented or reduced considerably by T cell depletion with a mouse IgG2a anti-Thy-1.2 mAb or high-dose cyclophosphamide or by rabbit ATG, provided it was initiated before starting the sensitizing injections of the rat antimouse T cell antibodies.     

鼠纤维介素在小鼠心脏移植急性排斥反应中的表达及其意义

目的　探讨小鼠同种心脏移植急性排斥反应期间鼠纤维介素 (mfgl2 )在移植心脏组织中的表达及其与组织病理学改变的关系。方法　采用BALB/c小鼠到C5 7BL/ 6小鼠的颈部异位心脏移植作为同种排斥反应模型 ,以抗mgfl2多克隆抗体干预 ,并设同系小鼠心脏移植对照组。采集移植心组织标本作病理学检查 ,以免疫组织化学方法测定mfgl2在移植心脏组织细胞上的表达 ,并对mgfl2的表达进行半定量分析。结果　同系移植对照组移植心脏组织结构正常 ,未见mfgl2表达 ;同种移植组移植心脏组织出现进行性坏死 ,大量单个核细胞浸润 ,并伴有mfgl2的表达 ,且血管内皮细胞表达mfgl2 ;抗mfgl2抗体干预组移植心脏组织损伤较轻 ,移植物的存活时间延长 (P <0 .0 1) ,巨噬细胞、淋巴细胞的浸润和mfgl2表达量也显著减少。结论　mfgl2表达水平与排斥反应所致移植心脏病理损害程度相关 ;抗mfgl2抗体干预能显著减少移植心脏巨噬细胞、淋巴细胞的浸润 ,明显延长移植心脏存活时间。     

Competitive equality of donor cells expressing a disparate MHC antigen following stem cell-enriched bone marrow transplantation

INTRODUCTION: Bone marrow cells expressing foreign MHC antigens survive poorly after transplantation. Stable mixed hematopoietic chimerism requires reconstitution with a relatively large number of foreign bone marrow cells and intensive depletion of host cells. In addition, when foreign MHC-transduced autologous bone marrow cells are transplanted, prolonged hematopoietic transgene expression requires extensive host conditioning. The competitive disadvantage associated with engraftment of donor cells expressing foreign MHC antigens is thought to result from a defect in engraftment secondary to donor-host incompatibility or immunologic resistance by the host. METHODS: We used a limiting-dilution competitive repopulation assay with cells from HLA-A2.1 transgenic mice to determine whether and to what extent foreign MHC antigen expression impairs engraftment in C57BL/6 hosts. Transplants were performed with Hoechst 33342 fluorescence-sorted side population (SP) cells, a subset of bone marrow enriched for stem cells. RESULTS.: Transplantation with 250 stem cell-enriched HLA-A2.1-transgenic side population cells successfully competed with nearly 5000 host C57BL/6 side population cells to produce stable long-term mixed chimerism. There was a direct relationship between the number of transplanted donor HLA-A2-expressing cells and the percentage of HLA-A2-expressing cells in the peripheral blood of reconstituted C57BL/6 mice (r2=0.1799, P=0.031). This correlation was maintained in secondary transplant recipients. CONCLUSIONS: HLA-A2-expressing hematopoietic cells do not have an engraftment defect when transplanted into C57BL/6 hosts and immunologic resistance did not limit chimerism following lethal irradiation. These results may have relevance to understanding long-term gene expression after hematopoietic stem cell based gene therapy.     

Induction of indefinite survival of fully allogeneic cardiac grafts and generation of regulatory cells by intratracheal delivery of alloantigens under blockade of the CD40 pathway

BACKGROUND: The authors previously showed that intratracheal delivery (ITD) of donor splenocytes induced prolonged survival of fully allogeneic cardiac grafts in mice. In this study, this treatment protocol was combined with blockade of the CD40 pathway in an attempt to induce operational tolerance. METHODS: CBA mice were given donor splenocytes (1x107) or Kb peptide (100 microg) by ITD with or without antibody specific for mouse CD40 ligand (MR1, 200 microg) 7 days before transplantation of a C57BL/10 heart. Also, splenocyte (5 x 107) from primary recipient CBA mice given ITD of donor splenocytes or Kb peptide plus MR1 were adoptively transferred into naive CBA secondary recipients 7 days after the pretreatment and C57BL/10 hearts were transplanted into those recipients the same day. RESULTS: ITD of donor splenocytes and Kb peptide induced prolonged survival of cardiac grafts (median survival time [MST], 74 and 56 days, respectively), whereas naive control mice and mice pretreated with syngeneic splenocytes had acute graft rejection (MST in both groups, 7 days). When MR1 was included, all grafts survived indefinitely (>200 days), but mice pretreated with MR1 alone had graft rejection (MST, 54 days). Mice bearing cardiac grafts had acceptance of skin grafts from C57BL/10 but not BALB/c mice, demonstrating that operational tolerance was induced. Secondary recipients given adoptive transfer of splenocytes from primary recipients of the combined treatment had acceptance of C57BL/10 grafts, suggesting that regulatory cells were generated within 7 days of pretreatment. CONCLUSIONS: ITD of donor splenocytes or Kb peptide under blockade of the CD40 pathway induced operational tolerance and generated regulatory cells.     

Induction of operational tolerance and generation of regulatory cells after intratracheal delivery of alloantigen combined with nondepleting anti-CD4 monoclonal antibody

BACKGROUND: We previously showed that intratracheal delivery of alloantigen induced prolonged survival of fully allogeneic cardiac grafts in mice. Here, this treatment protocol was combined with nondepleting anti-CD4 monoclonal antibody (mAb) to induce operational tolerance. METHODS: CBA (H-2k) mice were pretreated with intratracheal delivery of whole splenocytes from C57BL/10 (H-2b) mice or a 15-mer Kb peptide, with or without intraperitoneal administration of nondepleting anti-CD4 mAb (YTS177). Seven days later, C57BL/10 hearts were transplanted into the pretreated CBA mice. In addition, some naive CBA mice underwent adoptive transfer of splenocytes from pretreated CBA mice and transplantation of a C57BL/10 heart on the same day. RESULTS: Untreated CBA mice rejected C57BL/10 cardiac grafts acutely (median survival time, 12 days). Mice given intratracheal delivery of whole splenocytes or Kb peptide demonstrated prolonged graft survival (median survival time, 84 and 76 days, respectively). Concurrent administration of YTS177 and intratracheal delivery of splenocytes or Kb peptide resulted in indefinite graft survival. Mice with long-surviving C57BL/10 cardiac grafts showed acceptance of skin grafts from C57BL/10 mice but not BALB/c mice, demonstrating that operational tolerance had been induced. Adoptive transfer of splenocytes from mice pretreated with intratracheal delivery of splenocytes or Kb peptide plus YTS177 induced indefinite survival of cardiac grafts in secondary recipients, indicating that regulatory cells had been generated. CONCLUSION: In a murine model, intratracheal delivery of donor splenocytes or Kb peptide combined with YTS177 induced operational tolerance and generated regulatory cells.     

A novel MyD88 inhibitor attenuates allograft rejection after heterotopic tracheal transplantation in mice

BackgroundAfter lung transplantation, the major complication limiting the long-term survival of allografts is obliterative bronchiolitis (OB), characterized by chronic rejection. Innate immune responses contribute to the development of OB. In this study, we used a murine heterotopic tracheal transplantation mouse model to examine the effects of a newtype of innate immune inhibitor, TJ-M2010–5.MethodsSyngeneic tracheal grafts were transplanted heterotopically from C57BL/6 mice to C57BL/6 mice. Allografts from BALB/c mice were transplanted to C57BL/6 mice. The allograft recipients were treated with TJ-M2010–5, and anti-mouse CD154 (MR-1). The grafts were harvested at 7, 14, and 28 days and evaluated by histological and real-time RT-PCR analyses.ResultsIn untreated allografts, almost all epithelial cells fell off at 7 days and tracheal occlusion reached a peak at 28 days. However, the loss of the epithelium and airway obstruction were significantly improved in mice treated with TJ-M2010–5 combined with MR-1. The relative mRNA expression levels of pro-inflammatory cytokines were upregulated in allogeneic tracheal grafts, and treatment with the two drugs reduced the production of pro-inflammatory cytokines and infiltration of inflammatory cells.ConclusionsIn heterotopic tracheal transplantation models, TJ-M2010–5 combined with MR-1 could ameliorate the development of OB.     

Induction of transplantation tolerance in adults using donor antigen and anti-CD4 monoclonal antibody.

The T-cell-mediated immune response usually results in the rapid destruction of organ allografts transplanted between murine strains incompatible for major and minor histocompatibility antigens. This response may be modified by pretreatment with either donor-specific antigen or anti-CD4 monoclonal antibody. Previous work by others has shown that combined treatment of mice with soluble protein antigens and anti-CD4 monoclonal antibody can produce antigen-specific B cell unresponsiveness that continues long after the nonspecific immunosuppressive effect of the mAb treatment has resolved. Following this principle we have shown that adult C3H/He mice can be made specifically unresponsive to vascularized C57BL/10 cardiac allografts by pretreating the recipient with donor alloantigen under the cover of a brief course of mAb against CD4. A full-dose response analysis shows that the dose of mAb is critically important for the successful induction of tolerance. Tolerance induction using this protocol is dependent on treatment with donor major histocompatibility complex antigens and occurs in the presence of marked depletion but not complete elimination of the CD4+ T cell subset. The unresponsiveness to alloantigen is antigen specific, as determined by the ineffectiveness of third-party (C57BL/10) alloantigen when combined with anti-CD4 mAb to induce long-term survival of BALB/c allografts in C3H/He recipients. The tolerant state is specific and effective in the long-term as indicated by the specific acceptance of C57BL/10 skin grafts in recipients with surviving C57BL/10 cardiac allografts. This study provides a simple method for the successful induction of specific transplantation tolerance in the adult across a full H-2 major and minor antigen mismatch strain combination. The results illustrate the important role of the CD4 molecule in the T cell response to alloantigen in vivo and suggest possibilities for the therapeutic manipulation of complex immune reactions.     

Bovine sertoli cells colonize and form tubules in murine hosts following transplantation and grafting procedures

The contribution of somatic cells to nonrodent male germ cell transplantation success has not been well established due to lack of cell type-specific markers to distinguish donor cells from host cells. In the present study, we first screened antibodies and a lectin to identify markers suitable for unequivocal distinction between germ cells and Sertoli cells in bovine testes compared with mouse testes. Anti-vimentin and the Dolichos biflorus agglutinin (DBA) lectin detected only bovine Sertoli cells and spermatogonia, respectively; anti-NONO and anti-GCNA1 detected only mouse Sertoli and germ cells, respectively. The outcome of transplanting bovine testis cells into nude mouse testes was then studied using these markers. Our results clearly showed that immature bovine Sertoli cells survive and colonize mouse testes at 2.5 months after transplantation and that tubular structures composed of donor Sertoli cells formed adjacent to murine tubules within the host mouse testis. Bovine germ cell colonization and survival in mouse testes after transplantation were confirmed, but this was restricted to areas of bovine Sertoli cell colonization. In addition, ectopic grafts of intact bovine testis tissue and cell aggregates from hanging drop cultures were placed under the back skin and testis capsule of nude mice. Bovine Sertoli cells in ectopic grafts and aggregates were able to form tubular structures, and some bovine germ cells were observed around 2 months after implantation. This study therefore identifies a practical strategy to assess the outcome of testicular cell transplantation using different antibodies and a lectin to distinguish bovine cells from mouse cells. It identifies an approach that can readily be adapted to study other nonrodent species.     

Alpha beta TCR+ T cells play a nonredundant role in the rejection of heart allografts in mice.

BACKGROUND: Although the transplantation of solid organs and cellular grafts is a clinical routine, the morbidity and mortality associated with immunosuppression is significant. This could be avoided by the induction of donor-specific tolerance. To develop targeted antirejection strategies and regimens to induce donor-specific tolerance, cell populations in the recipient-mediating rejection of solid organ and cellular grafts must be defined. In this study we examined the role of alpha beta-TCR+ cells in the rejection of allogeneic heart grafts, by use of knockout (KO) mice deficient in the production of alpha beta-TCR+ T cells. METHODS: C57BL/6-TcrbtmlMom (alpha beta-KO) and C57BL6/J (B6) recipient mice were transplanted with B10.BR/SgSnJ (B10.BR) or BALB/c heart allografts. Animals also received bone marrow from normal B10.BR donors, followed by donor-specific or third-party heart transplants. RESULTS: Naive B6 control mice rejected B10.BR and BALB/c grafts within 16 days. In striking contrast, B10.BR and BALB/c heart allografts were indefinitely accepted in unmanipulated alpha beta-KO mice. The immune responsiveness was restored after bone marrow transplantation from normal donors. After bone marrow transplantation major histocompatibility-disparate BALB/c third-party heart grafts were rejected, whereas donor-specific grafts were still accepted. CONCLUSIONS: alpha beta-TCR+ T cells play a nonredundant role in the rejection of heart allografts in mice. Bone marrow chimerism is associated with donor-specific transplantation tolerance.     

Development of stable mixed T cell chimerism and transplantation tolerance without immune modulation in recipients of vascularized bone marrow allografts

A consistent majority (62.5%) of immunologically unmodified rat recipients transplanted with vascularized hind-limb bone marrow allografts across a semiallogeneic transplant barrier developed tolerance with absence of graft-versus-host disease. A minority of recipients (37.5%) demonstrated lethal GVHD. Transplantation tolerance in the majority was associated with the induction of stable low-level mixed T cell chimerism, including donor CD5+, CD4+, and CD8+ lymphocytes. Chimeras were specifically immune nonresponsive to host alloantigenic determinants. These results emphasized a potentially important mechanism for low-level stable mixed lymphoid chimerism (SMLC) in tolerance induction, independent of immune suppressive effects due to irradiation or immunopharmacologic intervention. These vascularized bone marrow transplantation (VBMT) results may establish the experimental foundation for a novel approach to stem cell transfer and bone marrow transplantation.     

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     

Experimental challenge for the treatment of duchenne muscular dystrophy using a vascularized free muscle graft

Following free vascularized normal muscle graft in mice, a study was made to determine whether dystrophin expression is possible in dystrophin-deficient muscles. In this study, dystrophic C57BL/10 ScSn-mdx mice were used as recipients and normal C57BL/10 ScSn mice as donors. A free vascularized quadriceps muscle 8.0 × 6.0 × 6.0 mm in size was orthotopically transplanted into a muscle defect produced in the recipient mouse. The diameter of the sutured vessels was about 0.4 mm. Transplantation was successful in 7 of 20 mice. At 12 weeks after the transplantation, the grafted muscle was examined by immunocytochemical stain using antidystrophin antibody. This study showed that dystrophin was expressed in the transplanted muscle but not in the adjacent recipient quadriceps muscle, suggesting that grafted donor cells with dystrophin failed to migrate into dystrophic muscle cells and fuse together. However, since the grafted normal skeletal muscle successfully survived and normal dystrophin was expressed in almost all the grafted muscle fibers, the possibility was suggested that the function of muscular dystrophy muscle can be compensated by complete replacement with a larger muscle. © 1994 Wiley-Liss, Inc.     

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.     

Long-term survival of xenogeneic heart grafts achieved by costimulatory blockade and transient mixed chimerism

BACKGROUND: Xenotransplantation holds great promise in clinical medicine, but is limited by the vigorous rejection response elicited against solid organs transplanted across species barriers. In this study, we investigated the role of anti-CD40L monoclonal antibody (mAb) in inducing xenogeneic mixed chimerism and donor-specific heart transplantation tolerance. METHODS: One day before heart transplantation, mice were injected intraperitoneally with anti-mouse CD8/NK1.1/Thy1.2 mAbs. On day 0, the mice received 3 Gy total body irradiation (TBI), an intravenous injection of unseparated bone marrow (BM) harvested from F344 rats, and an intraperitoneal injection of hamster antimouse CD40L mAb, MR1. Heart grafts from F344 rats were heterotopically transplanted into the abdomen of B6 mouse recipients. Using flow cytometric analysis of peripheral white blood cells, we assessed donor hematopoiesis at various times after bone marrow transplantation (BMT). RESULTS: Chimerism subsided gradually and disappeared completely 18 weeks after BMT. The cardiac graft survived permanently, even after the mixed chimerism disappeared. To determine if the mice acquired donor-specific tolerance, second rat heart grafts were transplanted 120 days after the first heart transplantation. The second transplanted hearts were also accepted over 60 days. Histological analysis revealed no remarkable vasculopathy in the coronary vessels at any stage. CONCLUSIONS: These findings clearly show that costimulatory blockade plays an important role in inducing xenochimerism, and that transient mixed chimerism can induce permanent acceptance of rat to mouse cardiac xenografts. Transplantation of xenogeneic bone marrow cells under costimulatory blockade at the time of heart transplantation may induce transplantation tolerance.     

Spontaneous acceptance of mouse kidney allografts is associated with increased Foxp3 expression and differences in the B and T cell compartments

Spontaneous acceptance of organ allografts can identify novel mechanisms of drug-free transplantation tolerance. Spontaneous acceptance occurs in both mouse kidney transplants and rat liver transplants however the early immune processes of mouse kidney acceptance have not been studied. Acceptance of C57BL/6 strain kidney allografts in fully MHC-incompatible B10.BR recipients was compared with rejection (REJ) of heart allografts in the same strain combination. Graft infiltrate and antibody deposition were examined by immunohistochemical staining. Expression of mRNA was measured by quantitative real-time PCR. Apoptosis was examined by TUNEL staining. The majority of kidney allografts were accepted long-term and induced tolerance (TOL) of donor-strain skin grafts, showing that acceptance was not due to immune ignorance. There was an extensive infiltrate of T cells in the TOL kidney that exceeded the level in REJ hearts but subsequently declined. The main differences were deposition of IgG2a antibody in REJ that was absent in TOL, more B cells infiltrating TOL kidneys and a progressive increase in the ratio of CD8:CD4 cells during rejection. There was also significantly greater Foxp3 mRNA expression in TOL. Kidneys from RAG-/- donors were accepted, showing that donor lymphocytes were not necessary for acceptance. Neutralising antibodies to TGF-β administered from day 0 to day 6 did not prevent TOL. On the basis of cytokine expression and apoptosis there was no evidence for immune deviation or deletion as mechanisms of acceptance. In accord with the findings of spontaneous acceptance of liver allografts in rats, the main difference between mouse kidney TOL and heart REJ was in the B cell compartment. The major difference to rat liver allograft acceptance was that apoptosis of infiltrate did not appear to play a role. Instead, increased Foxp3 expression in TOL kidneys implies that regulatory T cells might be important.     

Different kinetics of obliterative airway disease development in heterotopic murine tracheal allografts induced by CD4+ and CD8+ T cells

BACKGROUND: Both T and B cells have been shown to be implicated in the pathogenesis of bronchiolitis obliterans syndrome, which is considered to represent chronic lung allograft rejection. However, the relative contributions of T cells and alloantibodies in the pathogenesis of the disease are still unknown. In this study, we used an heterotopic murine tracheal transplantation model to determine the contribution of these components of the immune system in the pathogenesis of posttransplant obliterative airway disease (OAD). METHODS: Tracheal allografts from BALB/c and HLA-A2-transgenic (HLA-A2+) mice were heterotopically transplanted into C57BL/6, CD4-knockout (KO), CD8-KO, Ig-KO, and Rag1-KO mice. In additional experiments, recipient mice were pretreated with depleting antibodies against CD4+, CD8+, and NK1.1+ cells. Development of OAD was determined by histopathology at days 10, 30, 60, 90, and 180 after transplantation. RESULTS: HLA-A2+ allografts transplanted into C57BL/6, CD8-KO, and Ig-KO mice demonstrated OAD lesions by day 30. In contrast, allografts transplanted into CD4-KO mice showed no OAD lesions at day 30, partial OAD development by days 60 and 90, and complete OAD development by day 180. No OAD development was observed in allografts transplanted into Rag1-KO mice. Treatment with anti-NK1.1 antibody did not show any effect on posttransplant OAD development. In contrast, anti-CD4+ or anti-CD8+ antibody treatments partially reduced the OAD histopathology and combined anti-CD4/CD8 antibody treatment further abrogated the histopathology of the disease. CONCLUSION: These results show that both CD4+ and CD8+ T cells have a role in the pathogenesis of OAD and that natural killer cells and alloantibodies are not necessary for the development of this disease.