The antigenicity of sequential polypetides. II. The antigenicity of some sequential polymers including several related to collagen.

The antigenicity in guinea-pigs of a series of sequential polymers has been studied. Almost all the polymers had a repeating sequence of three amino acids and with few exceptions glycine was one of the three residues and proline or a proline homologue one of the others. As a result the majority of the peptides used probably possessed at least in part, the collagen type of triple helix, although with the exception of (Gly-Pro-Gly) all these polymers were antigenic inducing both a humoral and cell-mediated response. With (D-Ala-Gly-D-Pro) no humoral response was obtained but there were excellent cell-mediated reactions. The mutual cross-reactivity, both humoral and cell-mediated, between (Gly-Pro-Ala) and (Pro-Ala-Gly) emphasized the importance of the sequence in the body of the polymers rather than the sequence at the free ends in determining specificity. This is confirmed by the absence of cross-reactivity of both of these polymers with (Ala-Pro-Gly). With a series of samples of (Ala-Gly-Pro) of increasing single chain weight average molecular weight ranging from 2,000 to 15,000 the most immunogenic for cell-mediated reactions was that of lowest molecular weight, but for humoral responses immunogenicity ran parallel with increasing molecular weight with the exception of the polymer of highest molecular weight, which was almost insoluble.