IMMUNOLOGICAL-TOLERANCE - SELF-NONSELF DISCRIMINATION VERSUS COSTIMULATORY FACTORS AND 2ND SIGNALS

An attempt is made to assess the total number of the theoretically pos sible antigenic epitopes, the number of lymphocyte clones and the numb er of epitopes on cell surface antibody of a clone may be able to reco gnize. We suggest that the structures of recognizing antibody sites of a human are far from random and derived from a limited number of stru ctures adapted to the recognition of pathogenic agents. The probabilit y of recognition for a random epitope-like structure is likely to be v ery small. Discriminative power of BCR and TCR binding sites, together with T-helper control, should be sufficient for prevention of periphe ral autoimmune response, but second-signal-type controls should not be neglected as supplementary mechanisms to prevent such response.