Specific elimination of cytotoxic cells. II. Reduction of cytotoxic activity by adsorption on monolayers results from removal of cytotoxic cells and not from inhibition of their activity.

Cytotoxic lymphocytes produced by in vitro sensitization to H-2 alloantigens may be adsorbed efficiently and specifically on monolayers of spleen lymphocytes attached to poly-l-lysine-coated polystyrene. Greater than 16-fold median reduction in activity resulted from adsorption to the target-type monolayer while adsorption to the attacker-type monolayer resulted in a less than two-fold median reduction. Since this reduction could have resulted from competitive inhibition by detached monolayer cells rather than from sticking of the cytotoxic cells to the monolayer, experiments were performed to distinguish between these possibilities. The inhibitory properties of a nonadherent population were tested directly by addition to a different attacker-target combination in which its killing properties were irrelevant but in which the H-2 genotype of detached monolayer cells was appropriate to cause competitive inhibition. No significant inhibition was observed; and this indicated that reduction of activity in an adsorbed population results from removal of the cytotoxic cells and not from inhibition by detached monolayer cells competing with the labeled targets for attackers.