The frequency of effector cells in populations containing cytotoxic T lymphocytes

Abstract A new approach for the direct enumeration of effector cells in populations containing cytotoxic T lymphocytes is described. Stable lymphocyte‐target cell conjugates are formed during centrigugation at room temperature of mixtures containg cytotoxic lymphocytes and target tumor cells. Various types of lymphocyte‐target cell conjugates can be formed, the composition of the conjugate being dependent upon the ratio of lymphocytes to target cells during the conjugation process. The number of conjugates formed is highest at equal lymphocyte and target cell concentrations. At least 35% of the BALB/c anti‐EL4 peritoneal exudate lymphoid cells can conjugate to target cells and the majority of the conjugated lymphocytes are also killer cells. The variation in cytolytic activity of lymphoid cells with time following immunization and the differences in the lytic activity of immune lymphoid cells from various lymphoid organs are due to differences in the actual number of effector cells capable of conjugating with target cells.