ISOTYPE-ASSOCIATED RECOGNITION OF ALLERGEN EPITOPES AND ITS MODULATION BY ANTIGEN DOSE

The existence of competing and blocking IgG antibodies and their inter relationship with IgE antibodies was investigated in the IgE immune re sponse of CBA/J mice to bee venom phospholipase A(2) (PLA(2)) and keyh ole limpet haemocyanin (KLH). Minute doses of antigen induced high tit res of both IgE and IgG antibodies, whereas large doses elicited high IgG responses but only weak IgE antibody titres. Immunization with min ute doses of antigen led to the production of antibodies with class-as sociated epitope specificities (designated epitopes G for IgG and E fo r IgE antibodies), and therefore no competition was observed. For IgG antibody production, G epitopes were immunodominant and IgG antibodies directed to E epitopes were produced only after immunization with an increased immunogen dose. Under this condition IgG antibodies recogniz ing the E epitopes acted as blocking antibodies competing with IgE ant ibodies for binding to E epitopes, the immunodominant epitopes for the IgE response. The data demonstrate the existance of distinct immunodo minant antigenic determinants for IgE and IgG antibodies on PLA(2).