Unseparated and CD45RA+ and CD45RO+ PBL-T, respectively, were stimulated by CD2 monoclonal antibodies T11₂ and T11₃ (1/3000 v/v) in the presence or absence of SRBC (30 μl 5% SRBC for 10⁶ cells), Sepharose bound CD3 monoclonal antibody OKT-3 (1/100 v/v) in the presence or absence of IL-2 (10 U/ml) or autologous irradiated (50 Gy) PBMO (30% of total cell number) and PBMO only. Supernatants were harvested after 60 hours and the IL-10 content of each (results expressed in pg/ml; detection limit (min) 10 pg/ml) was determined by using ELISA. Cell growth was measured by the incorporation of [³H]-thymidine after four days. Results are expressed as the mean cpm of triplicate cultures. SD < 20%.