Maintenance of hyporesponsiveness to antigen by a distinct subclass of T lymphocytes

Immunization with increasing doses of SRBC, in excess of 10⁸, results in a progressive decline in the anti SRBC PFC response. This hyporesponsive state is antigen specific and is reflected in a decrease of both T helper and B antibody forming activity. The authors asked whether the apparent defect of T helper activity reflected a) an absence of αSRBC helper T cell activity, or b) the presence of SRBC specific suppressor T cells within the hyporesponsive population. The results indicate that at least a portion of hyporesponsiveness noted after antigen exposure to large doses of antigen can be ascribed to specific suppressor T cell activation. Fractionation of the suppressive T cell population using Ly antiserum showed that specific suppressive activity was mediated by a subclass of T cells (Ly2⁺), distinct from that committed to express helper function (Lyl).