DEPRESSION OF DELAYED HYPERSENSITIVITY BY PRETREATMENT WITH FREUND-TYPE ADJUVANTS II. MECHANISM OF THE PHENOMENON.

Recipient guinea-pigs pretreated with Freund's complete adjuvant alone show depressed 4 hr (Arthus) reactions following passive transfer of antiserum to bovine γ-globulin and human serum albumin. Recipient outbred guinea-pigs and inbred rats also show depressed 24 hr delayed reactions following passive transfer of immune peritoneal exudate cells and serum. This indicates that Freund's complete adjuvant depresses certain inflammatory responses. Donor guinea-pigs and inbred rats pretreated with FCA alone and then immunized with BGG in FCA transfer smaller 24 hr reactions to normal recipients than comparable donor animals which have not been pretreated with FCA. This suggests that pretreatment with FCA depresses the central state of delayed hypersensitivity which normally follows immunization with BGG in FCA. These two findings may explain why pretreatment with FCA depresses the 4 and 24 hr skin reactions which otherwise follow immunization with antigen in FCA. [ABSTRACT FROM AUTHOR]