A hapten-specific Ir gene.

When mice of different strains were immunized with a conjugate of 2-phenyloxazolone (phOx) and chicken serum albumin (CSA), the antibody response was controlled by an Ir gene (Ir-phOx). H-2 alleles d and f were associated with a high response, k and a with an intermediate response, and allele b with a low response. The effect of the Ir gene was clear-cut in anti-carrier antibodies of the primary and the secondary response when the concentrations of anti-carrier antibodies varied between 1 and 350 microgram/ml. Anti-hapten antibodies reached a ceiling of ca. 1000 microgram/ml that was unaffected by the Ir gene. Before the ceiling was reached, antihapten antibodies were also subject to the control of the Ir-phOx gene. When the same carrier CSA was coupled with other haptens, BOC-ABA-Tyr or NO2phOx, antibody responses were not under the control of the Ir-phOx gene. This gene is probably responsible for the differences that have been observed earlier in delayed hypersensitivity and antibody responses to skin painting by phOx.