Association of defective feedback suppressor T cell activity with autoimmunity in NZB mice.

A "feedback suppressor T cell" highly dependent on signals from Ly 1 T helper cells for activation is described. The signal from the Ly 1 cell binds to Fc-like receptors on macrophage membranes. The feedback suppressor cell expresses all three Ly antigens as well as the Qa 1 antigen on its surface, is very sensitive to low doses of cyclophosphamide, disappears relatively rapidly after adult thymectomy, and cannot be demonstrated in NZB mice 6 weeks or older.