Antitubular basement membrane antibodies in renal allograft rejection

In a patient with an episode of acute renal allograft rejection, antibodies to tubular basement membranes (TBM) were noted by direct immunofluorescence in a renal biopsy and by indirect immunofluorescence in the serum. The serum antibodies decreased gradually and became undetectable 3 months after the rejected kidney was removed. Anti-RBM antibodies eluted from the rejected kidney were capable of binding in vitro to TBM but not to glomerular basement membranes (GBM) in 39 of 40 human kidneys and various animal kidneys. The specificity was confirmed by blocking studies showing inhibition with ultrasonicated human TBM but not with GBM preparations. Passive transfer experiments showed that anti-TBM antibodies were able to bind in vivo to normal rabbit kidneys, although they could not elicit an inflammatory response. The possible mechanisms of production of anti-TBM antibodies and their potential significance in graft loss are discussed.