Isolation of a murine liver-specific alloantigen, F antigen, and examination of its immunogenic properties by radioimmunoassay.

The autoantibody response induced in mice by alloimmunization with liver-specific F antigen is an example of the circumvention of humoral self-tolerance. The F molecule has been isolated and shown to be a protein with a mol. wt. of 40 000 Daltons which migrated as a beta-globulin. The purified antigen retains both the immunogenic and antibody-combining properties of crude liver homogenate. Successful iodination of the protein allowed the establishment of a radioimmunoassay which demonstrated high titers of antibodies in responder strains. At the same time it was clearly shown that no antibody could be detected, either as a result of syngeneic immunization or as a result of alloimmunization in nonresponder strains. The characteristics of the F antigen immune response distinguish it from that induced by other proteins.