Kidney antigens active in isoimmunization. I. The antigenic diversity.

Isoimmunization of rabbits with kidney extracts and Freund's adjuvant leads to the development of responses to a multiplicity of autoantigens. If a large number of kidneys is pooled, there is increased probability that responses directed toward isoantigens can also be detected. Such immunization thus results largely in antisera that possess multiple specificities, but the amount of antibody directed toward each specific antigen varies from one antiserum to another. Advantage can be taken of these uneven responses by different animals, to enumerate the variety of responses to uniquely separable sets of determinants, by carefully selecting the antisera. In immunodiffusion studies, lines for such separable antigens can be sorted in an unambiguous manner. A total of five such antigens has now been found in kidney, three of which are kidney-specific and two of which are shared with liver. A sixth antigen, separable from liver, may be only a minor constituent of kidney, and was not directly detected in kidney extracts. It is important that fresh concentrated extracts of kidney homogenates be used. The detection of isoantigens requires concentrated extracts prepared from individual kidneys.