Clonal activation of cytotoxic lymphocyte precursors by monoclonal anti-CD3 antibody: analysis of feeder cell requirements

Activation of cytotoxic lymphocyte precursors (CLP) by the mitogenic monoclonal anti-CD3 antibody OKT3 was studied under limiting dilution (LD) culture conditions. One out of 2–6 E-rosette-purified T cells gave rise to a cytotoxic T cell (CTL) clone when cultured in the presence of OKT3 (0.2–2 ng/ml), recombinant IL-2 (100 U/ml), and irradiated feeder cells. Clonal CLP activation was optimally supported by a combination of E-rosette-depleted non-T feeder cells with small numbers of T cells added back. Among the cell lines tested, Fc-receptor-bearing monocytic cell lines U937 and HL-60 were efficient feeder cells whereas T cell lines (Jurkat, Molt-4, Ke37) did not support clonal CLP activation. These data indicate that clonal activation of CLP and differentiation into cytotoxic effector cells under LD culture conditions are critically influenced by the type and number of feeder cells used.