Restriction of primary responses to the IgG class and dependency of IgM responses on secondary immunization for the copolymers of L-glutamic acid, L-tyrosine, and L-alanine*

Primary responses to the linear polymers of L-glutamic acid, L-tyrosine, and Lalanine are restricted to the IgG class of antibodies. The appearance of specific IgM antibodies against these antigens is dependent upon secondary immunization, in contrast to many classical antigenic systems. The presence of an IgM response was verified by a direct plaque-forming cell assay, the inhibition of direct plaques by an antiserum specific for mouse µ-chain, and the physical separation of IgM and IgG GAT-specific antibodies by gel filtration. Preimmunization of the appropriate nonresponder strain with GAT or GT inhibits both the secondary IgM and IgG responses to GAT-MBSA and GT-MBSA, respectively. The tolerance observed is due to the induction of suppressor cells as demonstrated by cell transfer experiments.