Adherent splenocytes from tumor-bearing mice (control versus NK-depleted) influence the expansion and activity of memory T cells.

Primary CTL cultures from naive and BW-Sp3 tumor-bearing mice that were or were not devoid of NK cells were restimulated for 5 days in vitro. Nonadherent cells were removed from the resulting cultures, and the adherent cells (source of regulatory monocytes = 1° A-CTL) were used for subsequent restimulation of spleens from intraperitoneally BW-Sp3(B7-1) immunized mice (called memory spleens). (A) CTL activities of resulting secondary CTL cultures (1 memory spleen/adherent fraction derived from 1 restimulated primary spleen) are represented as the percentage of suppression of the CTL activity observed in the absence of regulatory monocytes. (B) Arginase activity was measured in adherent fractions of secondary CTL cultures. The concentrations are represented as quantity produced per 10⁶ adherent cells. All results in panels A and B are expressed as mean values of 3 experiments ± SEM. Comparative statistical analysis of α-ASGM-1–treated and nontreated conditions was done (P ≤ .0005). (C) Suppression of memory CTL restimulation in the presence of a constant number of adherent regulatory monocytes. For secondary CTL cultures with constant T/M proportions (1 memory spleen/2 × 10⁶ 1° A-CTL), adherent cells were isolated from primary CTL cultures derived from tumor-bearing mice (12 days after tumor inoculation) following 3 days of in vitro restimulation. (D) Arginase activity in the regulatory fraction before addition of memory CTL to initiate secondary CTL cultures.