ANTIGENICITY OF POLYPEPTIDES (POLY ALPHA AMINO ACIDS) : XII. IMMUNOLOGICAL STUDIES WITH A NEW GROUP OF SYNTHETIC COPOLYMERS

A new group of synthetic random polymers of α-L-amino acids has been studied for immunogenicity. With the glutamic acid and alanine copolymers, those consisting of almost equimolar amounts of the two (G₆₀A₄₀ and G₄₀A₆₀) were effective antigens in rabbits whereas those with higher glutamic acid contents (G₇₅A₂₅, G₉₀A₁₀) were poor antigens. The substitution of alanine by valine or leucine (G₇₅V₂₅ and G₈₀Leu₂₀) produced copolymers which were poor antigens in rabbits but effective in guinea pigs. L₇₀A₃₀, although capable of "non-specifically" precipitating serum proteins, was shown not to be antigenic in either rabbits or guinea pigs. The introduction of alanine into glutamic acid and lysine polymers (GLA series) enhanced the immunogenicity of the terpolymers, i.e., GLA30 > GLA20 > GLA10 > GL. The mechanism by which this may be accomplished is discussed as possibly being related to the reduction of the interactions between glutamyl and lysyl residues which allows the carboxyl groups to act as strong immunogenic determinants.