Plaque-forming cells in man. II: Evidence of the existence of active suppressor cells in peripheral blood of normal plaque-forming cell non-responders

When the immunoglobulin secretion of 172 normal healthy individuals was investigated with the protein-A plaque assay, 12 persons (7%) did not develop any plaque-forming cells (PFC) in cultures of pokeweed mitogen (PWM)-activated unfractionated peripheral blood lymphocytes (PBL), incubated for 6 days. The effect of irradiation on normal PFC responders and non-responders was also investigated; 2000-rad-irradiated non-responder T lymphocytes co-cultured with autologous untreated B lymphocytes restored the PFC response to normal levels. The evidence of a high level of suppressor activity in non-responder T lymphocytes was further demonstrated by the decreased PFC response of normal B lymphocytes co-cultured with untreated non-responder T lymphocytes.