Loss of autoreactive B cell tolerance and production of autoantibodies in chronic kidney allograft rejection in mice

Abstract Loss of autoreactive B cell tolerance and production of autoantibodies have been observed in patients undergoing chronic rejection. However, how autoreactive B cells lose their tolerance, and the role of autoreactive antibodies in chronic rejection remains an enigma. Recent observations from our laboratory that autoreactive B cells with a transcriptome profile of innate B cells accumulate in transplanted kidneys diagnosed with antibody-mediated rejection led us to hypothesize that (i) the loss of autoreactive B cell tolerance occurs primarily in the inflamed kidney and (ii) autoantibodies are contributing to graft rejection. In this study, we developed acute and chronic mouse kidney transplant models to test these hypotheses. Donor-specific antibody responses were assayed using donor MHC coated multiplex beads. Autoantibodies were detected with Hep-2 autoantibody detection kit and quantified with an image analysis pipeline in CellProfiler. The presence of autoantibody secreting cells was confirmed by graft tissue culture, and accumulation of autoreactive B cells was confirmed by ex vivo Nojima cultures. We found that autoantibodies were produced during chronic and acute kidney allograft rejection, even when donor MHC-specific antibody was inhibited with CTLA-4Ig. Remarkably, autoantibodies specific for cytoplasmic, nuclear and nucleolar antigens dynamically changed over time, suggesting rapid epitope spreading. Furthermore, there was an enrichment of autoreactive B cells and autoantibody secreting cells in the graft. Taken together, our mouse models complement data from rejecting biopsies, demonstrating a loss of autoreactive B cell tolerance and accumulation of autoantibodies within rejecting allografts. Supported by grant from NIH R01AI148705