The attacker: target-cell ratio and serum effects on in vitro cell-mediated immunity

Sera collected from mice rejecting an allogeneic tumor and showing arming activity for normal splenocytes increased target-cell lysis by immune cells when low (less than or equal to 25:1) attacker:target-cell ratios (A:T) were used but inhibited cytotoxicity at higher (100:1) A:T. The importance of this methodologic variable in studies of serum activity on cellular cytotoxicity is emphasized and the possible mechanisms are discussed.