A stepwise breakdown of B-cell tolerance occurs within renal allografts during chronic rejection

Autoantibodies detected after kidney transplantation may contribute to chronic rejection. We and others have previously described the organization of immune effectors into functional intragraft tertiary lymphoid tissue, a site where breakdown of B-cell tolerance may occur. To test this, we performed a comprehensive analysis of 26 chronically rejected kidney grafts. Antibodies were screened by indirect immunofluorescence on HEp2 cells, a procedure that detects antibodies to intracellular antigens, and monkey kidney sections, which detects kidney tissue autoantigens. The incidence of anti-HEp2 autoantibodies was significantly higher in graft explant culture supernatants than in patient sera. Reactivity against monkey kidney sections was detected in almost half of culture supernatants with anti-HEp2 autoantibodies. A local enrichment in T helper 17 and B-cell-activating factor (CD257) correlated with intragraft production of anti-HEp2 antibodies. A decrease in Tregs and a symmetric increase of activated OX40 (CD134)-expressing CD4+ T cells were found in grafts in which anti-kidney autoantibodies were produced. Thus, a stepwise breakdown of B-cell tolerance occurs within the graft during chronic rejection. Hence, the intragraft microenvironment interferes with peripheral deletion of autoreactive immature B cells that, in turn, produce antibodies against intracellular autoantigens. When intragraft immune regulation is insufficient, spreading of the local response against kidney autoantigens is favored.