It has been shown that copolymers of glutamic acid and lysine having ratios of 6:4, 7:3 or 5:5 are antigenic in about 40 to 50% of Hartley strain guinea pigs. A 6:4 copolymer of glu-lys having a molecular weight as low as 5000 was also antigenic. Within the dosage limits studied, the amount of antigen injected in complete Freund's adjuvant did not appear to affect significantly the immune response. Both “immediate” and “delayed” type skin reactions were noted in the guinea pigs. With the hyperimmune sera injected intraperitoneally, recipient animals did not exhibit either the “immediate” Arthuslike or “delayed” reactions. However, these same sera could evoke good passive cutaneous anaphylaxis (PCA) reactions and sensitize guinea pigs for passive systemic anaphylaxis. Some speculations have been advanced to explain the behavior of the glu-ala and glu-tyr copolymers as well as the poor over-all reactions with the glu-lys copolymers.
The order of decreasing sensitivity in the test for the production of antibody was systemic anaphylaxis, PCA and “active intracutaneous anaphylaxis of the ‘immediate’ type.” With the systems employed the molecular weight of the glu-lys copolymer had little effect on the cross-PCA reactions when compared on a weight for weight basis.