An unusual suppression of immune response: Pretreatment with poly(Glu 60,Phe 40) suppresses response to poly(Glu 60,Phe 40)

The synthetic random copolymer poly(Glu 60,Phe 40) (GPhe) is an excellent immunogen in SWR/J(H-2 q) mice. The intravenous injection of soluble GPhe by itself led to antibody production and GPhe-specific T-lymphocyte proliferation. The proliferating lymphocyte was sensitive to anti-Thy 1.2 and anti-Ly 1 antisera. A subsequent immunization with GPhe should therefore lead to an enhanced response. Yet, a single intravenous injection of an aqueous solution of GPhe suppressed the immune response to a subsequent immunization with GPhe in CFA as measured by GPhe-specific plaque-forming colonies, ELISA, T-cell proliferation, and delayed-type hyper-sensitivity. The suppression was not transferable from pretreated mice into normal or irradiated syngeneic recipients with either sera or lymphoid cells. The antibody generated from the pre-treatment could not be responsible for the suppression as injection of SWR anti-GPhe antibody into SWR/J mice enhanced, rather than suppressed, the response to the subsequent immunization with GPhe. Pretreatment of mice with a rabbit anti-idiotypic antiserum produced against (SWR anti-GPhe antisera) had no effect on the immune response to GPhe. Thus, the suppression cannot be explained by a simple B-cell tolerance mechanism. This type of unusual suppression was observed only with mice of H-2 q haplotype and not with mice of H-2 haplotypes a and k which are also responders to GPhe.