Stimulation of circulating autoantibody levels in the rat with established progressive passive Heymann nephritis

Rats with established progressive passive Heymann nephritis (PPHN) were stimulated with tubular nephritogenic antigen derived from rat kidney fraction 3 (rKF3) or heterologous antibody to the eKF3 antigen. Rats stimulated with antigen had elevated levels of circulating autoantibody and increased amounts of rat IgG in a beaded pattern around the glomerular capillaries. The brush border (BB) region of the proximal convoluted tubules also stained for rat IgG. Rats stimulated with antibody had similar changes, but in addition the injected antibody was demonstrated in the glomerular deposits and in the BB region of the proximal convoluted tubules. Proteinuria was markedly increased in the antibody injected rats. This study indicates that the cells of the 'primed' immune system of rats with PPHN can be stimulated by 'additional' rKF3 antigen or antibody to it, to produce increased levels of circulating autoantibody. It is suggested that the progression of PPHN is dependent on the availability and access of the nephritogenic autoantigen to the immune system and that autoantigen may be released by autoantibody.