Studies on the product of antigenic recognition. III. Nature of PAR

The product of antigenic recognition (PAR) is an antigen-antibody complex with granulotactic activity. The following results support his conclusion. PAR generated by cell-bound or shed T-cell RS or the recognizing structure of T alloantisera and alloantigen can be destroyed by heating at 56 degrees C for 30 min, because of inactivation of a heat-labile component supplied by alloantigen. Recognizing partners of these complexes are heat-stable. They form PAR anew when alloantigen is added or upon confrontation with anti-RS serum. They are also capable of inducing anti-RS sera. PAR preparations composed of these recognizing structures and antibodies to them are heat-inactivated at much higher temperatures, because both partners of the complex are relatively heat-stable. Heat-labile PAR complexes (recognizing structures and alloantigen) pass anti-mouse immunoglobulin immunosorbent, but are retained specifically by alloantiserum (via alloantigen of the complex) or by anti-RS serum (via RS of the complex) bound to the column.