“…In previous reports, we have shown that growth of the Landschiitz ascites carcinom a (LAC) in mice is as sociated with im pairm ent of cell-mediated immune responses [8], m acrophage activities in vivo and in vitro [6,7] and the production, by splenic T cells, of various lymphokines [5]. The capacity of the tum our to subvert delayed-type hypersensitivity reactions and cytokine production has been observed in both nor mal anim als and in hosts pretreated with high dose cyclophospham ide (Cy) [5], an agent believed to de plete selectively the precursors of T-suppressor (Ts) cells [9,12,13,15], The latter observation suggests that the im m unosuppressive action of the LAC is in dependent o f Ts.…”