Strain 2 guinea pigs immunized with 1 µg of 2,4-dinitrophenyl guinea pig albumin (DNP-GPA) containing an average of six DNP groups/molecule have no detectable antibody-secreting cells (direct or indirect plaque-forming cells) up to 28 days after immunization. As previously demonstrated, these animals lack an immune response (IR) gene, linked to the gene complex controlling strain 13 histocompatibility antigens, which controls the response to DNP-GPA.
Nonimmunized non-responder strain 2 animals and non-responder offspring of a backcross between strain 2 and (2 × 13)F1 guinea pigs have normal numbers of lymphocytes capable of binding 125I-DNP-GPA to their surface, indicating that these animals have no quantitative deficit in precursors of anti-DNP antibody-forming cells. Moreover, when strain 2 guinea pigs are immunized with 100 µg of DNP-GPA, they produce anti-DNP antibodies containing a fraction of high affinity molecules similar to that present in similarly immunized strain 13 animals. This indicates that strain 2 animals have no deficit among precursor cells bearing high affinity receptors. Thus, the IR gene controlling the immune response to DNP6GPA does not control the frequency of precursor cells bearing receptors which bind DNP-GPA.