PPARγ ligands subvert CTL suppression by tumor-associated macrophages. Splenocytes from 5- to 7-week BW-Sp3 progressors were restimulated in vitro with irradiated BW-Sp3(B7-1) for 5 days, and a distinction was made between (1) CTL activity in total splenocyte cultures (Total), (2) CTL activity in splenocytes magnetically depleted in CD11b⁺ cells (CD11b-depleted), (3) CTL activity in CD11b-depleted splenocytes, supplemented with 15% freshly prepared tumor-associated macrophages at the initiation of the culture (15% TAMs), and (4) CTL activity in CD11b-depleted splenocytes, supplemented with 15% freshly prepared tumor-associated macrophages and the appropriate inhibitors at the initiation of the culture (15% TAM + inhibitors). The cytotoxic activity in all cultures was tested using ¹¹¹In-labeled BW-Sp3(B7-1) cells as targets at a 100:1 effector-target ratio. Results show the average ¹¹¹In-release ± SD of triplicates.