Immunogenicity of fully defined lysine LAG dodecapeptides in guinea-pigs: with a note on an antigenic cooperation effect in the delayed immune response.

The immunogenicity of a series of dodecapeptides was evaluated in random-bred guinea-pigs. The peptides were synthesized by an economical two-phase approach specifically developed for the production of gram-amounts of peptide antigens. The peptides contain L-leucine, L-alanine, glycine and L-lysine and differ from each other by number and distribution of lysine residues. Some of the peptides carry DNP groups at their N-terminus. With the exception of one (5,11-Lys-LAG-OEt), all peptides induced a state of cellular immunity as evaluated by delayed dermal reactions and macrophage migration inhibition. Some peptides also induced the formation of circulating antibodies. Immunogenicity appears to increase with the number of basic groups and is more pronounced with DNP peptides. Delayed dermal responses are highly specific since even peptides closely related to the immunogen did not elicit reactions. Reactions were however observed when some mixtures of closely related peptides not used for immunizing the animal were administered. This `antigenic cooperation' effect is discussed briefly.