Abstract: Objective There are few detailed reports up to now about the newly developed anti-HLA antibodies(Ab) after living donor renal transplantation(RTx). We retrospectively investigated the relationship between the development of anti-HLA Ab and the incidence of humoral rejection(HR) in living donor RTx recipients. Methods The subject included 87 patients who received living kidney allografts at kidney center, Tokyo Women's Medical University. PRA assay(Flow PRA screening test) was performed in all the recipients one day before and six months after the RTx. Meanwhile, the donor specificity of Ab was determined by single bead assay(LAB Single antigen analysis). Graft biopsies were performed respectively as well at 0 hour, 2 weeks, 6 months, 1 year after the RTx. We retrospectively studied these recipients with anti-LA Ab to determine the relationship among HR rate, donor specificity and prognosis. Results In 87 recipients, 59 cases(67.8%) showed negative/negative results and 28 cases(32.2%) showed negative/positive results according to the values of pre-post-transplant Flow PRA screening test. As for the 59 recipients without anti-LA Ab, 8 cases(13.6%) developed HR during 6 months posttransplantation, yet no case did so thereafter. Among the 28 cases with anti-LA Ab, 13 cases(46.4%) had donor-specific Ab and 15 cases(53.6%) had non-onor specific Ab as determined by LAB Single antigen analysis. Eleven(39.3%) of the 28 cases with anti-LA Ab showed evidence of antibody mediated humoral rejection in the graft biopsies performed within 6 months and all of them were detected having donor specific Ab. Furthermore, in the graft biopsies performed 1 year after the RTx, 5 of 11(45.5%) cases mentioned above showed persistent evidence of humoral rejection. All these cases lost their grafts in the coming 2 years and returned to regular hemodialysis. Comparably, no HR happened in other 15 recipients with non-onor specific Ab all the way. The 3-year survival rate of renal graft in posttransplant anti-LA Ab negative and positive groups were 96.6% and 75.0% respectively(P<0.01). Conclusion The development of anti-LA antibodies is markedly associated with higher incidence of acute humoral rejection and worse prognosis in living donor RTx recipients, especially in those with donor-specific Ab. Cautious monitoring for the appearance of anti-LA antibodies should be done after transplantation.

Key words: renal transplantation, living donor, humoral rejection, anti-HLA antibody