Induction of tolerance in adult guinea-pigs by two antigen dosage levels and by antigenic competition.

The effect of prior injection of increasing doses of dinitrophenylated bovine serum albumin (DNP-BSA) mixed in Freund's complete (FCA) or incomplete (IFA) adjuvants on the antibody response to a subsequent challenge with an optimal immunizing dose of DNP-BSA in FCA has been examined and compared with the effect of competition with the unrelated antigen bovine gamma-globulin (BGG). An unresponsive state was induced by pretreatments with either a minimal dose of antigen, a large antigen excess or a competitive mixture in FCA. The specificity of this unresponsiveness was ascertained by the normal response of pretreated animals to the unrelated antigen arsanilic-human albumin (ARS-HSA). Prior injection of either a minimal dose (0,2 mug), an antigen excess (20 mg) of DNP-BSA or an optimal dose (20 mug) of DNP-BSA mixed with an excess of BGG, incorporated in IFA, also induced a specific tolerance to DNP-BSA. The former treatment induced a low zone tolerance whereas both later treatments induced a high zone tolerance.