Inability of normal and activated thymus-derived cells to act as cytotoxic effector cells against antibody-coated targets.

Thymus lymphocytes activated in vitro by a T cell mitogen (concanavalin A (Con A)) did not form Fc rosettes nor were they cytotoxic against untreated or antiserum-coated target cells. Con A activated spleen cells were cytotoxic against target cells, but they did not display an increased cytotoxic effect against antibody-coated YAC targets, when compared to normal spleen cells. Con A-activated spleen cells as well as cells activated by a mixed lymphocyte culture did not form Fc rosettes. Thus, activated cytotoxic T cells did not form Fc rosettes nor did they cause cytotoxicity on antibody-coated target cells. Antibody coating of the target cells did not suppress expression of cytotoxicity of activated T cells.