Studies of the antigens involved in an immunologic renal tubular lesion in rabbits.

Rabbits injected with nonglomerular components of rabbit kidney incorporated in Freund's complete adjuvant develop a lesion characterized a) extensive interstitial fibrosis, tubular degenerative changes, and sparse focal lymphocytic infiltrates; b) the deposition of IgG and C3 in a granular pattern along the basement membranes of proximal convoluted tubules; and c) functional tubular defects if the lesions are severe. The antibodies were eluted from kidneys with such lesions and labeled with fluorescein isothiocyanate. It was shown that these fluorescein-labeled eluates reacted with the corresponding antigens in the tubular deposits and also with the antigens present in the brush border and/or cytoplasm of the proximal tubules. The antigens are found in proximal tubules of the kidney but not in brain, lung, heart, liver, spleen, bowel, muscles, or urine. They appear to be soluble but may also be present in the plasma membrane.