Studies on the induction and time course of repressionof delayed hypersensitivity in the mouse by low and high doses of antigen.

Abstract

CAF1 and CF-1 female mice pretreated with small or large quantities of the protein antigens chicken egg albumin or human serum albumin had their capacities to develop delayed hypersensitivity and some humoral antibodies in response to injection of these antigens in Freund's incomplete adjuvant specifically repressed. Repression following a single intraperitoneal injection of 10 mg of human serum albumin in saline was maximal at 2 weeks. Two appropriately spaced pretreatments were approximately 100-fold more effectual than one in eliciting repression, perhaps because of a secondary antibody response. Pretreatment with antigen in an inefficient variety of Freund's incomplete adjuvant also induced immunologic repression both at high (100 and 10 mg) and very low (optimal = 0·01 γg) doses; but this repression was weaker than that following pretreatment with antigen in saline. One experiment comparing four injection routes for relative capacity to induce repression showed no one clearly superior to the others, although the intravenous route gave some indication of being so. Repression affecting induction of delayed hypersensitivity lasted for 12 weeks in CF-1 and 30 weeks in CAF1 mice, receded slowly thereafter, and was not followed by spontaneous sensitization. Among humoral antibody responses, pretreatment-induced repression affected Arthus sensitization, and passive haemagglutinin, precipitin and passive cutaneous anaphylaxis antibody production, roughly in descending order. Data from these experiments seem most compatible with the idea that the repression studied is active rather than passive and due, perhaps, to a humoral antibody which represses sensitization.