Selective and specific inhibition of 24 hour skin reactions in the guinea-pig. 3. Depression of cytophilic and haemolytic antibodies by pretreatment with antigen and the effect of irradiation.

Dvorak and Flax (1966) and others reported that adult guinea-pigs pretreated with soluble antigens showed depressed immune responses following immunization with the same antigens in Freund's complete adjuvant. These depressed immune responses included haemolytic and cytophilic antibody and delayed hypersensitivity as well as antibody measured by passive cutaneous anaphylaxis and haemagglutination. This communication describes further studies on the effect of pretreatment with bovine γ-globulin rather than antigen. Guinea-pigs given 1 mg of alum precipitated bovine γ-globulin prior to immunization with 50 μg bovine γ-globulin (BGG) in Freund's complete adjuvant show depressed haemolytic and cytophilic antibody and delayed hypersensitivity. This depression is immunologically specific as pretreatment with alum precipitated egg albumin does not depress immune responses to bovine γ-globulin. In contrast, antibody measured by passive cutaneous anaphylaxis and haemagglutination is either unaffected or raised. Similarly, pretreatment with sheep red cells reduces the cytophilic antibody response to sheep red cells in Freund's complete adjuvant. This depression is long lasting and 1 mg alum precipitated BGG depressed the haemolytic antibody response to BGG in adjuvant given 6 months later and the delayed hypersensitivity response to BGG in adjuvant given 9 months later. Alum precipitated BGG given up to 6 days after immunization with BGG in adjuvant caused some depression of haemolytic antibody. However, this depression was transient and much less than the long lasting depression caused by pretreatment with alum precipitated BGG 7 days before immunization with BGG in adjuvant. The effect of irradiation followed by alum precipitated BGG on the immune responses to BGG in Freund's complete adjuvant was also studied. 300 r depressed haemolytic and haemagglutinating antibody but had no effect on cytophilic antibody or delayed hypersensitivity. There was no synergy between irradiation and pretreatment with BGG; the depression of immune responses caused by irradiation followed by alum precipitated BGG was no greater than the depression caused by the more effective agent when given alone.