Activation in vivo of a major antisuppressor T-cell pathway immediately after immunization. II. T-cell requirements for its expression.

Immunogens activate in vivo within 3-6 hr after injection a new and hitherto unrecognized T-cell pathway which interferes with T-cell suppression, therefore called antisuppression. An important soluble mediator with antisuppressor activity is detected in the serum of immunized animals within 3-6 hr. The mediator represents a unique form of complexes of Ig and antigen. The antisuppressor function of the complexes does not represent a direct "neutralizing" effect of the complexes on the effector T suppressor cells. The antisuppressor complexes activate an Ly2+ T cell which, with the interaction of an Ly123+ T cell, blocks completely T-suppressor-cell function. The biological significance of the T antisuppressor pathway is discussed.