Immunophenotyping of peripheral immunoregulatory as well as Th17A and Th22 cell subpopulations in kidney transplant recipients under belatacept or cyclosporine treatment

ObjectiveRegulatory Foxp3-expressing T cells (Tregs), IL-10-producing B cells (Bregs), and IDO-expressing dendritic cells (DCregs) downregulate inflammatory processes and induce peripheral tolerance, while Th17A and Th22 cell subpopulations are of proinflammatory nature. The aims of the study were to characterize and to enumerate peripheral Tregs, Bregs, and DCregs and Th17A and Th22 cell subpopulations in kidney transplant recipients (KTRs) under belatacept or cyclosporine treatment.MethodsForty-one KRT patients (30 under belatacept treatment and 11 under cyclosporine treatment) and 26 healthy donors (HDs) were included in the study. CD19⁺-expressing peripheral B lymphocytes were purified by positive selection. IL-10-producing B cells, CD4⁺/CD25^highFoxp3⁺, and CD8⁺/CD28^?Foxp3⁺ Tregs, CCR6⁺/CD123⁺/IDO⁺ DCs, as well as Th17A and Th22 cell subpopulations were quantitated by flow cytometry.ResultsOf the IL-10-producing Bregs, CD19⁺/CD24^high/CD38^high/CD5⁺, CD19⁺/CD24^high/CD38^high/CD10⁺, CD19⁺/CD24^high/CD38^high/CD20⁺, and CD19⁺/CD24^high/CD38^high/CD27^? had significant higher frequency in patients under belatacept treatment when compared with those under cyclosporine. Only CD19⁺/CD24^high/CD38^high/CD27⁺ and CD19⁺/CD24^high/CD38^high/CXCR7⁺ cells had significant higher frequency in patients under cycloporine treatment when compared to those under belatacept. The percentages of IDO-expressing pDC, CD4⁺/CD25^highFoxp3⁺, and CD8⁺/CD28^?Foxp3⁺ were significantly higher in the belatacept group when compared the cyclosporine one, while Th17A and Th22 cells had significant higher frequency in the latter group.ConclusionBelatacept seems to maintain and enhance, at least systemically, a tolerant profile to renal allograft in transplant recipients by means of higher circulatory frequencies of regulatory B, T and pDC subpopulations.     

The Effects of Different Induction Regimes on Serial Lymphocyte Subsets in Kidney Transplant Recipients: A Single Tertiary Center Experience

BackgroundImmunosuppressive therapy is the backbone of kidney transplantation in preventing acute rejection. T-cell depletion after doses of thymoglobulin is dose-dependent, as are their side effects. At the same time, basiliximab and other maintenance immunosuppressive drugs act at different signals on T lymphocytes. Therefore, studying the pattern of lymphocyte subset depletion depending on the induction regime given at transplantation could be an added tool in managing post-transplant recipients.MethodologyThis prospective observational study recruited kidney transplant recipients from August 2019 through April 2021 at the University of Malaya Medical Centre. Blood tests for lymphocyte subsets were taken at pre-transplant, 1 week, 1 month, 3 months, and 6 months post-transplantation. At transplantation, recipients received either basiliximab, low-dose thymoglobulin (cumulative dose: 1.5 mg/kg), or standard-dose thymoglobulin (cumulative dose: 5 mg/kg).ResultsA total of 39 patients were recruited: 38.5% received basiliximab (15 of 39), 15.4% received low-dose thymoglobulin (6 of 39), and 46.2% received standard-dose thymoglobulin (18 of 39). Absolute lymphocyte counts 1 week post-transplantation were 1.5 ± 0.84 × 10⁹/L for basiliximab, 0.7 ± 0.57 × 10⁹/L for low-dose thymoglobulin, and 0.1 ± 0.08 × 10⁹/L for standard-dose thymoglobulin (P < .001). The CD4+ and CD8+ counts were severely depleted in the standard-dose thymoglobulin group, with a statistically significant differenceup to 6 months post-transplantation. In the low-dose thymoglobulin group, the CD4+ and CD8+ counts were depleted at 1 week post-transplantation and recovered at 1 month post-transplantation. There was no difference in allograft function and incidence of allograft rejection across groups.ConclusionsThe effects on lymphocyte counts, CD4+ and CD8+, vary depending on the type and dose of induction immunosuppression. This could be a guiding tool in managing immunosuppression post-transplantation depending on the patient's immunologic risk.     

T cell receptor beta chain (TCR-Vβ) repertoire of circulating CD4+ CD25−, CD4+ CD25low and CD4+ CD25high T cells in patients with long-term renal allograft survival

The mechanisms underlying maintenance of renal allografts in humans under minimal or conventional immunosuppression are poorly understood. There is evidence that CD4⁺ CD25⁺ regulatory T cells and clonal deletion, among other mechanisms of tolerance, could play a key role in clinical allograft survival. Twenty‐four TCR‐Vβ families were assessed in CD4⁺ CD25^?, CD4⁺ CD25^low and CD4⁺ CD25^high T cells from patients with long‐term renal allograft survival (LTS), patients exhibiting chronic rejection (ChrRx), patients on dialysis (Dial) and healthy controls (HC) by flow cytometry. LTS patients presented a higher variability in their TCR‐Vβ repertoire, such decreased percentage of Vβ2⁺, Vβ8a⁺ and Vβ13⁺ in CD4⁺ CD25^low and ^high compared with CD4⁺ CD25^? subset and increased Vβ4 and Vβ7 families in CD4⁺ CD25^high T cells exclusively. Additionally, LTS patients, particularly those that were not receiving calcineurin inhibitors (CNI), had increased percentages of CD4⁺ CD25^high T cells when compared with Dial (P < 0.05) and ChrRx (P < 0.05) patients. Our results suggest that a differential expression of particular TCR‐Vβ families and high levels of circulating CD4⁺ CD25^high T cells in long‐term surviving renal transplant patients could contribute to an active and specific state of immunologic suppression. However, the increase in this T cell subset with regulatory phenotype can be affected by CNI.     

HLA‐DR expression and differential trafficking of monocyte subsets following low to intermediate risk surgery*

Reduced HLA‐DR expression on monocytes has been suggested as a predictive marker of immunosuppression following very high risk surgery, but there are few reports in lower risk surgery. In 32 patients undergoing low to intermediate risk surgery, blood samples were analysed by flow cytometry for HLA‐DR expression and numbers in both CD14^high and CD14^lowCD16+ monocyte subsets. The numbers of CD14^high monocytes increased at 24 h (mean (SD), 5.0 (2.2) vs 7.6 (3.9) × 10⁵ cells.ml^?1; p < 0.01) while CD14^lowCD16+ monocytes decreased (0.68 (0.36) vs 0.44 (0.36) × 10⁵ cells.ml^?1; p < 0.01). HLA‐DR expression was significantly reduced in both subsets by 24 h (mean (SD) fluorescent intensity 440 (310) vs 160 (130) for CD14^high and 1000 (410) vs 560 (380) for CD14^lowCD16+ subsets; p < 0.01). This reduction of monocyte HLA‐DR expression 24 h following lower risk surgery raises questions about the purported clinical utility of this biomarker as an early predictor of postoperative complications. Our results also suggest that surgery induces significant trafficking (i.e. mobilisation, margination and extravasation) of monocyte subsets, and that monocyte HLA‐DR depression is the result of a down‐regulatory phenomenon (decreased protein expression on each cell) rather than the differential trafficking of monocyte subsets.     

Lymphocyte subsets in renal allograft recipients with chronic hepatitis C virus infection.

BACKGROUND: The pathogenetic mechanisms of chronic hepatitis C virus (HCV) infection in renal allograft recipients are not well established. This study aimed to examine the relationship between altered immune status and HCV-related liver disease, by determining the changes in peripheral blood lymphocyte and natural killer (NK) cell subsets in these subjects. METHODS: Peripheral blood lymphocyte, NK cell and activation markers were detected by flow cytometry in renal allograft recipients with (TpC+) or without (TpC-) HCV infection, and compared with age- and sex-matched patients with post-transfusional chronic HCV infection (TfC+) and healthy controls. RESULTS: CD19+ cells were reduced in renal allograft recipients compared with controls. TpC+ subjects had increased CD3+CD8+ cells compared with controls, and increased CD3+DR+ cells but reduced CD4+ CD38+ and CD3-CD16/56+ cells compared with controls as well as TfC+ patients. TfC+ patients and controls had similar numbers and proportions for the lymphocyte subsets and NK cells. Chronic liver disease in HCV-infected renal allograft recipients was associated with increased CD3+CD16/56+ cells but reduced CD4+CD38+ cells. Reduction of CD3-CD16/56+ cells was noted in TpC+ subjects without liver disease. Yet among post-transfusional (TfC+) subjects this was associated with chronic hepatitis. CONCLUSIONS: Peripheral blood suppressor/cytotoxic T lymphocytes are increased, whereas activated helper/inducer T lymphocytes and NK cells are reduced, in renal allograft recipients with HCV infection. Increased non-MHC-restricted cytotoxic T cells and reduced NK cells are associated with the presence or absence of liver disease respectively. These data suggest that immune mechanisms are important in the pathogenesis of chronic hepatitis C after renal transplantation.     

Dynamic Analysis of B-Cell Subsets in De Novo Living Related Kidney Transplantation With Induction Therapy of Basiliximab

Background

Accumulative evidence has suggested B-cell–mediated alloimmune response plays an important role in kidney transplantation. Monitoring the dynamics of B-cell subsets could enhance understanding of B-cell immunology in clinical transplantation, and may facilitate optimization of current immunosuppressive regimens.

Patients and Methods

Between June 2011 and June 2012, 16 de novo living related kidney transplant recipients were enrolled in this study. All patients were given basiliximab as induction therapy. The maintenance therapy consisted of tacrolimus, mycophenolate mofetil (MMF), and steroids. Phenotype of B-cell subsets in peripheral blood was examined at day 0, day 1, day 3, day 7, day 14, month 1, month 3, and month 6.

Results

CD19⁺ B cells in peripheral lymphocytes significantly increased by 1.8–2.1 times within 1 month after transplantation, and recovered to the baseline level at month 3. Notably in B cells, CD5⁺CD19⁺B cells dramatically decreased by 45% at month 6. CD19⁺CD27⁺ memory B cells increased by 127% at month 6. B-cell activating factor receptor (BAFF-R) expression on the B-cell population was maintained at a high level of 91.7%–97.9%. Within 7 days after transplantation, Bm1 (IgD⁺CD38⁻) did not change apparently, Bm2 (IgD⁺CD38^int) significantly increased, whereas Bm2' (IgD⁺CD38^high, germinal center founder cells), Bm3+Bm4 (IgD⁻CD38^high, germinal center B cells), early Bm5 (IgD⁻CD38^int), and late Bm5 (IgD⁻CD38⁻) significantly decreased. After day 7, Bm1 stayed stable, Bm2 decreased to the baseline level (day 0), and Bm2' and Bm3+Bm4 kept decreasing, whereas early Bm5 and late Bm5 increased to baseline level. At month 6, Bm1 significantly increased, Bm2 was maintained at the baseline level, Bm2' constantly decreased to the lowest, and Bm3+Bm4 was slightly lower than the baseline, whereas early and late Bm5 increased to the baseline level.

Conclusions

The proportion of B cells in peripheral lymphocytes significantly increased at the early stage, whereas CD5⁺CD19⁺B cells consistently decreased after transplantation. Mature circulating B-cell subsets dynamically changed, especially at the early stage after transplantation, which might be attributed to the induction therapy.     

Dynamic changes of B‐cell compartments in kidney transplantation: lack of transitional B cells is associated with allograft rejection

B cells play an important role in the immune responses which affect the outcomes of kidney allografts. Dynamic changes of B‐cell compartments in clinical kidney transplantation are still poorly understood. B‐cell subsets were prospectively monitored using flow cytometry for 1 year in 98 kidney transplant recipients. Data were correlated with immunosuppression and clinical outcomes. An increase in the total population of B lymphocytes was observed during the first week after transplantation. The level of IgM^highCD38^highCD24^high transitional B cells reduced significantly up until the third month, with partial repopulation in the first year. Lower numbers of transitional B cells in the third month were associated with higher risk of graft rejection. IgM⁺IgD⁺CD27^? naive B cells did not change within follow‐up. IgM⁺CD27⁺ nonswitched memory B cells and IgM^?CD27⁺ switched memory B cells increased on post‐operative day 7. IgM^?CD38^highCD27^high plasmablasts showed similar kinetics during the first post‐transplant year, similar to transitional B cells. In conclusion, sensitized kidney transplant recipients as well as those with either acute or chronic rejection within the first post‐transplant year exhibited lower levels of transitional B cells. Therefore, these data further support the hypothesis that transitional B cells have a protective role in kidney transplantation.     

CD69 expression on peripheral CD8 T cells correlates with acute rejection in renal transplant recipients

BACKGROUND: The development of a noninvasive method to diagnose renal allograft rejection could prevent the complications associated with graft biopsy and allow more accurate surveillance of allograft function. The present study determines whether expression of CD69 on peripheral T lymphocytes of renal allograft recipients correlates with the presence of acute graft rejection. METHODS: Peripheral blood T lymphocytes from healthy volunteers, renal allograft recipients with elevated creatinine but no evidence of rejection on biopsy, and renal allograft recipients with biopsy-proven rejection were analyzed by flow cytometry for the expression of CD69 and various intracellular cytokines (interleukin-2, interferon-gamma). Results were then compared with the degree of rejection on biopsy. RESULTS: CD69 expression on CD3+, CD4+, and CD8+ T-cell subsets was low in controls and transplant recipients without allograft rejection. In contrast, patients with renal allograft rejection showed significantly elevated percentages of CD69+ cells in the CD3+ (P<0.01) and CD8+ subsets (P<0.01). The fraction of CD69+ and CD8+ T cells was found to be a more clinically useful test based on receiver-operator characteristics. CD69 expression on CD4+ T cells did not correlate with rejection. Significant intracellular cytokine levels were not detected in unstimulated T cells from any of the groups; stimulation with mitogens increased expression equally among the three groups. CONCLUSIONS: We demonstrate that expression of CD69 on CD3+ and CD8+ peripheral blood T cells correlates closely with the presence of acute graft rejection in renal allograft recipients. Measurement of this surface marker may provide a rapid, noninvasive, and accurate means by which graft rejection can be identified.     

Cytomegalovirus-specific regulatory and effector T cells share TCR clonality--possible relation to repetitive CMV infections

Cytomegalovirus (CMV) infections have a major impact on morbidity and mortality of transplant patients. Among the complex antiviral T‐cell response, CMV‐IE‐1 antigen‐specific CD8+ cells are crucial for preventing CMV disease but do not protect from recurring/lasting CMV reactivation. Recently, we confirmed that adoptive transfer of autologous IE‐1/pp65‐specific T‐cell lines was able to combat severe CMV disease; however, the control of CMV infection was only temporary. We hypothesized that CMV‐induced regulatory T cells (iTreg) might be related to recurring/lasting CMV infection. In fact, kidney transplant patients with recurring CMV infections expressed enhanced suppression on CMV response. Analysis of in vitro expanded CD4+ epitope‐specific cells revealed that CMV‐specific CD4+CD25^high Treg cells functionally suppress CD25^low effector T cells (Teff) upon epitope‐specific reactivation. Their phenotype is similar to iTreg – CD39^high/Helios‐/IL‐2^low/IFNγ^high/IL‐10±/TGFß‐LAP±/FOXP3+ and methylated foxp3 locus. Remarkably, in vitro expanded CD4+CD25^high iTreg share the same dominant TCR‐Vβ‐CDR3 clones with functionally distinct CD4+CD25^low Teff. Moreover, the same clones were present in freshly isolated CD4+CD25^high and CD4+CD25^low T cells suggesting their in vivo generation. These findings directly demonstrate that Teff and iTreg can differentiate from one “mother” clone with specificity to the same viral epitope and indicate that peripheral iTreg generation is related to frequent antigen appearance.     

Pre-transplant co-infusion of donor-adipose tissue derived mesenchymal stem cells and hematopoietic stem cells may help in achieving tolerance in living donor renal transplantation

Transplantation tolerance is still a Utopian dream for many transplanters. Mesenchymal stem cells (MSC) have shown immuno-modulatory and tolerogenic effects in experimental models. We present a 29-year-old male with end stage renal disease (ESRD) who was transplanted with HLA 4/6 matched kidney from 51-year-old father in June 2010 preceded by co-infusion of donor-adipose tissue derived mesenchymal stem cells (AD-MSC) and bone marrow derived hematopoietic stem cells (BM-HSC) under non-myeloablative conditioning for deleting rejecting T and B-cells. He has maintained fairly stable graft function with serum creatinine (SCr) between 1.5 and 1.8?mg/dL at 3 years post-transplant with absence of donor specific antibodies (DSA), normal protocol graft biopsy, and peripheral T-regulatory cell levels (pTregs) (CD127^low/?CD25^highCD4⁺) of 4.57% on zero immunosuppression since 6 months.     

CD154 Deficiency Uncouples Allograft CD8+ T‐Cell Effector Function from Proliferation and Inhibits Murine Airway Obliteration

Obliterative bronchiolitis (OB) limits the long‐term success of lung transplantation, while T‐cell effector mechanisms in this process remain incompletely understood. Using the murine heterotopic tracheal transplant model of obliterative airway disease (OAD) to characterize airway allograft rejection, we previously reported an important role for CD8⁺ T cells in OAD. Herein, we studied the role of CD154/CD40 costimulation in the regulation of allospecific CD8⁺ T cells, as airway rejection has been reported to be CD154‐dependent. Airway allografts from CD154^−/− recipients had significantly lower day 28 OAD scores compared to wild‐type (WT) recipients, and adoptive transfer of CD8⁺ T cells from WT recipients, but not CD154^−/− recipients, were capable of airway rejection in fresh CD154^−/− allograft recipients. Intragraft CD8⁺ T cells from CD154^−/− mice showed similar expression of the surface markers CD69, CD62L^low CD44^high and PD‐1, but markedly impaired IFN‐γ and TNF‐α secretion and granzyme B expression versus WT controls. Unexpectedly, intragraft and systemic CD8⁺ T cells from CD154^−/− recipients demonstrated robust in vivo expansion similar to WT recipients, consistent with an uncoupling of proliferation from effector function. Together, these data suggest that a lack of CD154/CD40 costimulation results in ineffective allospecific priming of CD8⁺ T cells required for murine OAD.     

Association of Higher CD4+CD25highCD127low,FoxP3+, and IL‐2+ T Cell Frequencies Early After Lung Transplantation With Less Chronic Lung Allograft Dysfunction at Two Years

Regulatory T cells (Treg) can regulate alloantigens and may counteract chronic lung allograft dysfunction (CLAD) in lung transplantation. We analyzed Treg in peripheral blood prospectively and correlated percentages of subpopulations with the incidence of CLAD at 2 years. Among lung‐transplanted patients between January 2009 and July 2011, only patients with sufficient Treg measurements were included into the study. Tregs were measured immediately before lung transplantation, at 3 weeks and 3, 6, 12, and 24 months after transplantation and were defined as CD4⁺CD25^high T cells and further analyzed for CTLA4, CD127, FoxP3, and IL‐2 expressions. Between January 2009 and July 2011, 264 patients were transplanted at our institution. Among the 138 (52%) patients included into the study, 31 (22%) developed CLAD within 2 years after transplantation. As soon as 3 weeks after lung transplantation, a statistically significant positive association was detected between Treg frequencies and later absence of CLAD. At the multivariate analysis, increasing frequencies of CD4⁺CD25^highCD127^low, CD4⁺CD25^highFoxP3⁺ and CD4⁺CD25^highIL‐2⁺ T cells at 3 weeks after lung transplantation emerged as protective factors against development of CLAD at 2 years. In conclusion, higher frequencies of specific Treg subpopulations early after lung transplantation are protective against CLAD development.     

The outcome of renal transplantation among systemic lupus erythematosus patients.

BACKGROUND: Clinical outcome of renal transplantation among systemic lupus erythematosus (SLE) patients remains a topic of controversy. Most of the previous reports were based upon small single-centre studies that were not always well-designed. METHODS: We conducted the retrospective analysis using data from USRDS and UNOS databases. Patients were divided into five groups based on the cause of end-stage renal disease (ESRD): diabetes mellitus (DM), SLE, glomerulonephritis, hypertension and other causes. Between 1990 and 1999, 2886 renal transplantation recipients with ESRD due to SLE were identified from a total of 92 844 patients. RESULTS: The mean follow-up period of this study was 4.7 +/- 2.4 years. While unadjusted analysis using Kaplan-Meier curves demonstrated an association between SLE and improved allograft survival compared with DM, in multivariate analysis the SLE group had worse allograft [hazard ratio (HR) 1.09, P < 0.05] and recipient (HR 1.19, P < 0.05) survival compared with the DM group. Subgroup analysis based on the type of donor showed that SLE patients who received deceased donor allograft had worse allograft and recipient survival (HR 1.14, P = 0.002 and HR 1.30, P = 0.001, respectively) compared with non-SLE deceased donor allograft recipients. Among living allograft recipients, there were no significant differences in either allograft or recipient survival compared with non-SLE recipients. CONCLUSIONS: SLE as a cause of ESRD in renal transplant recipients is associated with worse allograft and recipient survival compared with DM; this association is true for the entire population and for the recipients of deceased donor (but not living donor) transplant. Deceased donor allograft recipients have worse outcomes compared with living allograft recipients.     

Hyperlipidemia Alters Regulatory T Cell Function and Promotes Resistance to Tolerance Induction Through Costimulatory Molecule Blockade

Recent work from our laboratory has shown that hyperlipidemia promotes accelerated rejection of vascularized cardiac allografts in mice by inducing anti‐donor Th17 reactivity and production of IL‐17. Here, we show that hyperlipidemia also affects FoxP3⁺ regulatory T cells (Tregs). Hyperlipidemia promotes the development of Tregs that express low levels of CD25. Hyperlipidemia also promotes a decrease in central Tregs and an increase in effector Tregs that appears to account for the increase in the frequency of CD25^low Tregs. Alterations in Treg subsets also appear to lead to alterations in Treg function. The ability of FoxP3⁺, CD25^high_, CD4⁺ Tregs from hyperlipidemic mice to inhibit proliferation of effector T cells stimulated with anti‐CD3 and CD28 was reduced when compared with Tregs from control mice. Regulatory T cells isolated from hyperlipidemic recipients exhibit increased activation of Akt, and a reduction in Bim levels that permits the expansion of FoxP3⁺CD25^lowCD4⁺ T cells. Hyperlipidemic mice were also resistant to tolerance induction using costimulatory molecule blockade consisting of anti‐CD154 and CTLA4Ig, a strategy that requires Tregs. Together, our data suggest that hyperlipidemia profoundly affects Treg subsets and function as well as the ability to induce tolerance.     

Relationship of B cell alloantibodies to renal allograft survival.

To define the relationship of donor-specific B lymphocyte alloantibodies to renal allograft survival, longitudinal serum samples obtained pre- and post-transplantation were examined for antibodies cytotoxic to donor B lymphocytes. Ten of 17 renal allograft recipients had antibodies to donor B lymphocytes but not T lymphocytes either pre- and/or post-transplantation. Three patients underwent successful transplants despite preformed B cell antibodies; however, seven who developed B cell antibodies only after transplantation are either undergoing chronic rejection (4) or have had severe rejection crisis (3). Seven patients with no B cell antibodies have functioning grafts. In all cases, B cell antibodies were detected before biochemical and clinical evidence of rejection. Similar findings were noted when sera of 38 renal transplant recipients were examined for B cell antibodies cytotoxic to an unrelated panel of B lymphocytes. These results demonstrate that the development of B cell alloantibodies after transplantation is often associated with rejection and that successful renal transplantation can be performed across a positive B cell crossmatch.     

Influence of 15-deoxyspergualin on activated lymphocytes: Comparison of heart and renal rat transplantation models

Background. Among the immunological effects of 15-deoxyspergualin (DSG), its action on activated T lymphocytes with the interleukin 2 receptor (IL-2R) is controversial. Materials and methods. To investigate this action, we used rat heart and rat renal transplantation models in which Brown Norway rats (BN) served as the organ donors and Lewis rats (LEW) as the organ recipients. DSG was administered intraperitoneally to the recipients immediately after the operation. The percentage of IL-2R-positive cells and of CD4- and CD8-positive cells in the recipient spleen or allograft was evaluated. Results. The average survival period (days) of the BN heart or renal allograft in hosts treated with DSG was significantly longer than that in the untreated hosts. In the heart transplantation model, DSG decreased the percentage of IL-2R-positive cells and increased the CD4/CD8 ratio in the allograft. By contrast, in the renal transplantation model, DSG suppressed the percentage of IL-2R-positive cells in the spleen,but influenced neither the percentage of IL-2R-positive cells nor the CD4/CD8 ratio in the allograft. Conclusion. DSG extended allograft survival significantly in both heart and renal transplantation models. However, the influence of DSG on IL-2R-positive cells may be different in the two types of allografts. Received: March 30, 1998 / Accepted: September 2, 1998     

Triptolide inhibits donor‐specific antibody production and attenuates mixed antibody‐mediated renal allograft injury

Donor‐specific antibodies (DSAs) are major mediators of renal allograft injury, and strategies to inhibit DSAs are important in promoting long‐term graft survival. Triptolide exhibits a wide spectrum of antiinflammatory and immunosuppressive activities, and in autoimmune diseases it inhibits autoantibody levels. In this study, we investigated the suppressive role of triptolide in the generation of DSAs in transplant recipients. We found that triptolide treatment of skin allograft recipients in mice significantly suppressed the development of circulating anti‐donor‐specific IgG and effectively alleviated DSA‐mediated renal allograft injury, which led to prolonged allograft survival. In vitro studies revealed that triptolide inhibited the differentiation of B cells into CD138⁺CD27⁺⁺ plasma cells; reduced the levels of IgA, IgG, and IgM secreted by plasma cells; and repressed somatic hypermutation and class switch recombination of B cells. Moreover, triptolide‐treated recipients showed reduced numbers of B cells, plasma cells, and memory B cells in spleens and decreased numbers of T, B, natural killer (NK) cells, and macrophages infiltrating grafts. These findings highlight the importance of triptolide in suppressing DSAs and establish triptolide as a novel therapeutic agent for antibody‐mediated allograft rejection.     

Transferable Cardiac Allograft Acceptance Induced by Transfusion of Donor B Cells With Impaired Inducible Costimulator/B7h Allorecognition

ObjectiveDonor-specific transfusion (DST) of leukocytes with an impaired costimulatory signal has been proven to be an effective way to improve allograft survival. Inducible costimulator (ICOS) has been shown to play a crucial role in acute and chronic allograft rejection. To test the role of ICOS signaling during DST, we employed ICOS-Fc-targeted B cells as antigen of DST to challenge the allogeneic engraftment in vivo.Materials and MethodsA murine cardiac allograft model was employed using BALB/c donors and C57BL/6 recipients, while various transfusions were performed according to treatment protocols.ResultsAllograft survival was prolonged by infusion of ICOS-Fc-targeted B cells; however, allograft acceptance could not be achieved unless additional systemic injections of ICOS-Fc were given. Adoptive transfer of splenic CD4⁺ but not CD4⁺CD25^? subsets from long-term allograft survival (LTAS) mice to lightly irradiated naive recipients resulted in subsequent BALB/c allograft acceptance without additional immunosuppression.ConclusionsICOS/B7h signaling during direct allorecognition played an important role in prolonging allograft survival, and an allograft acceptance can be established by DST with complete blockade of ICOS/B7h in both direct and indirect allorecognition. Interestingly, this allograft acceptance was transferable and maintained at least partly by the immune regulation of CD4⁺CD25⁺ T cells. These findings may help to design a potential therapeutic treatment to prevent allograft rejection by DST in combination with ICOS/B7h blockade.