Nephrotoxic serum nephritis in rats. II. Preparation and characterization of a soluble protective factor produced by trypsin digestion of rat tissue homogenates.

A soluble protective factor, capable of absorbing nephrotoxic antibodies from anti-rat kidney serum, can be obtained in high concentration by tryptic digestion of rat kidney homogenate. The factor is no longer antigenic or at most only slightly so. It is stable at 60 degrees , destroyed by boiling, is non-dialyzable, can be precipitated by ammonium sulfate, but resists destruction by proteolytic and other enzymes. In accord with previous studies on the organ localization of the rat tissue antigen responsible for the production of nephrotoxic antibodies, the soluble protective factor, or antigen derivative, can be obtained by tryptic digestion of rat lung, skeletal muscle, heart, and liver.