Kinetics of CTL suppression induced by coculture with Meth A tumor cells. Coculture assays were performed with H-2^d anti-H-2^b CTLs as described in the text. T cells were cultured alone, or with Meth A cells for 0.5, 1, 2, or 3 hours, as indicated. CTLs were then positively selected by MACS and tested immediately in a 4 hour chromium release assay against EL-4 target cells.