Rabbit serum or globulin, containing antibody to rat collagen, injected intravenously or intracardially into normal or adjuvant-prepared rats becomes fixed in the basement membranes of renal glomeruli and, to a slight extent, of the tubules. When examined by ultraviolet light, this antibody can be identified in tissue sections by the yellow-green fluorescence occurring where the rabbit globulin, associated with the fixed collagen antibody, has reacted with fluorescein-conjugated anti-rabbit globulin from ducks. The reaction of the antibody to rat collagen with its antigen in the kidney is a primary factor in the production of the renal glomerular injury which occurs in rats prepared with adjuvant. Adjacent control sections failed to fluoresce when pretreated with unlabeled anti-rabbit globulin or when treated with heterologous conjugated anti-duck globulin from rabbits. The antibody to rat collagen remains in the kidney as long as 92 days and has been detected as early as 45 minutes after injection. When normal rabbit serum, rabbit anti-fish collagen serum, or rabbit anti-rat collagen serum absorbed with rat collagen was substituted for the rabbit anti-rat collagen serum, fixed antibody could not be demonstrated by fluorescence; but absorption of the anti-rat collagen serum with fish collagen did not affect the antibody fixation.
This series of immunologic tests indicates that the anti-collagen serum reacts with its homologous antigen, presumably collagen, in the basement membranes of renal glomeruli and tubules, and that specific antibody can be used to identify collagen in other tissues of the animal body.