Influence of renal transplantation in rats on glomerular and tubular immune complexes.

Kidneys were transplanted from rats with immune complex nephritis to normal rats to determine the role of circulating antibodies to renal antigens in the maintenance of immune complexes. Glomerular subepithelial immune complexes in nine proteinuric donor rats, actively or passively immunized with proximal tubular antigen Fx1A (active and passive Heymann nephritis), were studied at the time of transplantation and two to four and one-half months after transplantation to normal unilaterally nephrectomized recipient rats. These subepithelial IgG deposits and proteinuria persisted throughout the four-month period after transplantation. Tubular subepithelial immune complexes in the kidneys of nine rats, actively immunized with a distal renal tubular antigen, Tamm-Horsfall protein, were studied at the time of transplantation when donors had high circulating IgG antibody titers to Tamm-Horsfall protein and at one to eight weeks after transplantation. The abundant granular and nodular immune complexes of rat IgG and Tamm-Horsfall protein at the base of tubular cells were very rapidly cleared during the first two weeks after transplantation and were virtually absent by four weeks. The rapid clearance of tubular immune complexes after transplantation of kidneys from actively immunized rats followed a time course similar to that after passive immunization with antisera to Tamm-Horsfall protein. These findings support the concept that high titers of circulating antibodies to Tamm-Horsfall protein are required to prevent the rapid clearance of tubular immune complexes, a process that is facilitated by conditions of antigen excess at the surface of tubular cells.(ABSTRACT TRUNCATED AT 250 WORDS)