The antigenicity of native and tyrosylated neutral-salt-soluble rat collagen.

Neutral-salt-soluble collagen was extracted from rat skin and purified by repeated precipitation, resolution and dialysis. Part was reacted with N-carboxytyrosine anhydride and a collagen derivative containing 2·6 per cent tyrosine was recovered. Enrichment with tyrosine did not alter the optical rotation, denaturation temperature or electrophoretic mobility of the collagen. The antigenic properties of native and tyrosylated rat collagen were studied in rabbits and guinea-pigs by micro-complement fixation, tanned cell agglutination and agglutination-inhibition, passive cutaneous anaphylaxis and immediate and delayed skin hypersensitivity. The antigenicity of native collagen was demonstrated. Enrichment with a limited amount of tyrosine enhanced its antigenicity without altering its antigenic specificity and permitted a detailed analysis of the overall specificity of the immunological reaction. Use of the products of controlled degradation of collagen in the immunoassay systems implicitly defined the collagen molecule as responsible for the immune reaction. Collagenase-digestion products still possessed antigenic capacity.