Ir gene defects may reflect a regulatory imbalance. I. Helper T cell activity revealed in a strain whose lack of response is controlled by suppression.

A singular responsiveness to HEL was revealed in a peripheral lymphoid compartment of the genetically nonresponsive H-2b mouse. Although i.p. injection of HEL induces suppression and a lack of anti-HEL production, following footpad injection there is an early emergence in the popliteal lymph node (P-LN) of HEL-specific helper activity and plaque-forming cells. Furthermore, the early P-LN transiently expresses one of two T cell types needed for initiation of suppression. Delayed recruitment of the second required cell-type permits the induction of efficient suppression. There is only a short period during which there is concurrent representation of the two T cell subpopulations, and by mixing early and late deficient P-LN T cells, suppression could be established. The general implication of these results is that although a vigorous helper cell potential may exist in a strain nonresponsive to a multideterminant antigen, it can be obscured by a regulatory cell imbalance that results in the manifestation of a generalized Ir gene "defect."