The effect of alum-precipitated pyridine ragweed extract on guinea pigs: I. Arthus reactivity induced with a single low dose

Abstract

The antigenicity of alum-precipitated pyridine (APPR) and aqueous ragweed (ARE) extracts was evaluated in comparable groups of animals totaling 400. A single subcutaneous dose of 0.01, 0.10, 1.00, 10.00, 30.00, 50.00, or 100.00 μg of protein N, was injected. Intradermal tests with ARE were performed 5 to 136 days later. Gross and microscopic observations were made at 20 minutes, 4, 24, and 48 hours. The negative skin reactions at 20 minutes showed that neither APPR nor ARE, in the dosage levels used, caused immediate, that is, wheal and flare type of hyperscnsitivity, at least when dye was not injected concurrently. Neither APPR nor ARE induced delayed hypersensitivity, as evidenced by negative 24 and 48 hour intradermal tests on the immunized animals, irrespective of day tested or test dose used. Only the 4 hour, typically Arthus reactions, grossly and microscopica ly were positive in either APPR or ARE immunized animals. These results indicate that alum-precipitated pyridine ragweed extract is capable of producing a much greater immunological response. Reactions were induced earlier and were maximal in many more animals immunized with minimal single doses of APPR than with those receiving equivalent doese of ARE. Furthermore, this response persisted longer.