Effect of panel reactive antibodies on T cell immunity reinstatement following renal transplantation

BACKGROUND Chronic kidney disease is associated with immunological disorders,presented as phenotypic alterations of T lymphocytes.These changes are expected to be restored after a successful renal transplantation;however,additional parameters may contribute to this process.AIM To evaluate the impact of positive panel reactive antibodies(PRAs)on the restoration of T cell phenotype,after renal transplantation.METHODS CD4CD28null,CD8CD28null,natural killer cells(NKs),and regulatory T cells(Tregs)were estimated by flow cytometry at T0,T3,and T6 which were the time of transplantation,and 3-and 6-mo follow-up,respectively.Changes were estimated regarding the presence or absence of PRAs.RESULTS Patients were classified in two groups:PRA(-)(n=43)and PRA(+)(n=28)groups.Lymphocyte and their subtypes were similar between the two groups at T0,whereas their percentage was increased at T3 in PRA(-)compared to PRA(+)[23(10.9-47.9)vs 16.4(7.5-36.8)μ/L,respectively;P=0.03].Lymphocyte changes in PRA(-)patients included a significant increase in CD4 cells(P<0.0001),CD8 cells(P<0.0001),and Tregs(P<0.0001),and a reduction of NKs(P<0.0001).PRA(+)patients showed an increase in CD4(P=0.008)and CD8(P=0.0001),and a reduction in NKs(P=0.07).CD4CD28null and CD8CD28null cells,although initially reduced in both groups,were stabilized thereafter.CONCLUSION Our study described important differences in the immune response between PRA(+)and PRA(-)patients with changes in lymphocytes and lymphocyte subpopulations.PRA(+)patients seemed to have a worse immune profile after 6 mo follow-up,regardless of renal function.

Impact of human leukocyte antigen matching and recipients＇ panel reactive antibodies on two-year outcome in presensitized renal allograft recipients

Background Renal transplantation in sensitized candidates remains a highly significant challenge worldwide. The production of panel reactive antibody （PRA） against human leukocyte antigen （HLA） is a major risk factor in presensitized recipients. The aim of this study was to evaluate the impact of HLA matching and recipients＇ PRA on two-year outcome in presensitized renal allograft recipients. Methods We determined the percentage of panel reactivity and specificity of anti-HLA immunoglobulin （Ig） G antibodies in 73 presensitized renal allograft recipients compared with 81 unsensitized recipients （control group）. HLA genotyping of both recipients and corresponding donors was performed by PCR with sequence-specific primers （PCR-SSP）. We analyzed the factors influencing the early graft outcome （two-year rejection rates and survival rates of the grafts）, including HLA mismatching, class and degree of panel reactivity, and target antigen of donors. Results Presensitized recipients had a worse two-year outcome than unsensitized recipients （P=0.019 for rejection rate, P=0.01 for survival rate）. The difference in number of HLA-mismatched alleles with either 6-antigen matching （Ag M） standard or amino acid residue matching （Res M） standard was not significant between the rejection and non-rejection groups of presensitized recipients or between the graft survival group and graft loss group. Compared with the control group, recipients with both PRA-I and PRA-II antibodies had a significantly worse two-year outcome （P=0.001 for rejection rate, P=0.002 for survival rate）. The two-year outcomes of the peak PRA 〉50% group and its subgroup, at-transplant PRA 〉50% group, were significantly worse compared with the control group （P=0.025 and P=0.001 for rejection rate, P=0.043 and P=0.024 for survival rate）. The rejection rates of the at-transplant target antigen positive group and its subgroup, HLA-I target antigen positive group, were significantly higher than the control group （P=0.001 and P=-0.001）, target antigen negative group （P=0.003 and P=0.001）, and peak target antigen positive with negative at-transplant target antigen group （P=0.024 and ,0=-0.002）. Two-year graft survival rates of the target antigen positive group and HLA-I target antigen positive group were significantly lower than the control group （P=0.012 and ,P=0.001）. The two-year outcome of target antigen unknown group was similar to that of the target antigen positive group. Presensitized recipients with pre-transplant plasmapheresis or immunoadsorption （PRA prepared group） had a better but non-significant two-year outcome than the control group. However, the PRA unprepared presensitized recipients were different to the control group （P=-0.004 for rejection rate and P=-0.005 for survival rate）. Hyperacute rejection （HR） occurred in three recipients with positive HLA-I target antigen and without mismatch according to Res M and in one case with positive PRA-II （for an unknown target antigen）. No HR occurred in eight cases with positive HLA-II target antigens. Conclusions Pre-transplant PRA preparations might improve the access of presensitized patients to renal donors. Avoiding antigen-positive donors remains a fundamental measure in preventing HR and early rejections.

Alemtuzumab induction therapy in highly sensitized kidney transplant recipients

Background Immunosuppression for immunologically high-risk kidney transplant patients usually involves antithymocyte globulin induction with triple drug maintenance therapy. Alemtuzumab, a humanized anti-CD52 antibody, was expected to be a promising induction therapy agent for kidney transplantation. However, currently no consensus is available about its efficacy and safety. This study aimed to evaluate the efficacy and safety of alemtuzumab as immune induction therapy in highly sensitized kidney transplant recipients.Methods In this prospective, open-label, randomized, controlled trial, we enrolled 23 highly immunological risk patients （panel reactive antibody 〉20%）. They were divided into two groups： alemtuzumab group （trial group） and anti-thymocyte globulin （ATG） group （control group）. Patients in the alemtuzumab group received intravenous alemtuzumab （15 mg） as a single dose before reperfusion. At the 24th hour post-operation, another dosage of alemtuzumab （15 mg） was given. The control group received a bolus of rabbit ATG （9 mg/kg）, which was given 2 hours before kidney transplantation and lasted until the removal of vascular clamps when the anastomoses were completed. Maintenance immunosuppression in both groups comprised standard triple therapy consisting of tacrolimus, prednisone, and mycophenolate mofetil （MMF）. Acute rejection （AR） and infection episodes were recorded, and kidney function was monitored during a 2-year follow-up. X2 test, ttest and Kaplan-Meier analysis were performed with SPSS17.0 software.Results Median follow-up was 338 days. In both the alemtuzumab group and ATG group, creatinine and blood urea nitrogen values in surviving recipients were similar （P 〉0.05）. White blood cell counts were significantly reduced in the alemtuzumab group for the most time points up to 6 months （P 〈0.05）. One patient receiving alemtuzumab died for acute myocardial infarction at the 65th day post-operation. Two ATG patients died for severe pulmonary infection or cardiac and pulmonary failure. Cumulative 2-year graft survival rate was 90.9% in the alemtuzumab group and 81.8% in ATG group （P 〉0.05） respectively. There was one graft failure in the alemtuzumab group and two graft failures in ATG group, with all graft failures at tributed to rejection episodes. The alemtuzumab group had a 2-year cumulative freedom from rejection rate of 81.8%, compared with 72.7% for the ATG group （P 〉0.05）.Conclusion Alemtuzumab induction therapy for highly sensitized kidney transplant recipients is an effective and safe protocol yielding an acceptable acute rejection rate.

Expression characteristics of major histocompatibility complex class I-related chain A antibodies and immunoadsorption effect in sensitized recipients of kidney transplantation

Background Sensitized recipients have a high risk of immunological graft loss due to hyperacute rejection and/or accelerated acute rejection. The presence of major histocompatibility complex class I-related chain A （MICA） antibodies has also been described associated with an increased rate of kidney-allograft rejection. The aim of this study was to describe the expression of MICA antibodies in sensitized recipients of renal transplantation and evaluate its influence on the kidney transplantation recipients.Methods A total of 29 sensitized recipients were included in this study. All patients received the MICA antibodies detection before and after protein A immunoadsorption. Panel reactive antibody （PRA）, HLA-matches, acute rejection and postoperative one to four-week serum creatinine level were also collected and analyzed, respectively. No prisoners were used in this study.Results Eight patients （27.6%） in all 29 sensitized recipients expressed the MICA antibodies but did not show higher acute rejection rate than the non-expressed patients （3/8, 37.5% vs. 8/21, 38.1%; P=1.000）. Recipients with PRA 〉40% showed higher expression levels of MICA antibodies than the recipients with PRA 〈40% （7/16, 43.8% vs. 1/13, 8.3%; P=0.044）. HLA mismatch did not have any effect on the expression of MICA antibodies （P=1.000）. MICA antibodies positive group had higher serum creatinine level than the control in postoperative one week （（135.4±21.4） μmol/L vs. （108.6±31.6） μmol/L, P=0.036）, but no significant difference in postoperative four weeks （（89.0±17.1） μmol/L vs. （77.1±15.9） μmol/L, P=0.089）. MICA antibodies decreased significantly after protein A immunoadsorption.Conclusions MICA antibodies increase in the sensitized recipients, which have significant effects on the function of aliograft in early postoperative period. Protein A immunoadsorption can decrease MICA antibodies effectively in sensitized recipients.