Similarity of cellular recognition structures for histocompatibility antigens and of combining sites of corresponding alloan tibodies

Theoretical considerations on a possible similarity between recognition structures (RS) on immunocompetent cells and the antigen‐binding sites of alloantibodies aimed at the same target have been tested experimentally in the PAR assay with the aid of antisera directed against recognition structures (anti‐RS sera). It was found that the activity of an alloantiserum could be neutralized specifically by a corresponding anti‐RS serum. Conversely, the activity of an anti‐RS serum could be blocked specifically by a corresponding alloantiserum. The term “aliotype” is proposed for antigenic determinants residing on the combining region of alloantibodies and on corresponding recognition structures of lymphoid cells.