Suppression of naive 1B2⁺CD8⁺T cells response to L^d in vitro by cells from tolerant mice in the presence of exogenous IL-4. Naive1B2⁺CD8⁺ cells (1 × 10³cells/well) from 2C_F1 mice were used as responder cells and stimulated by 3 × 10⁵ cells/well of irradiated (20 Gy) splenocytes from BYJ mice. 1B2⁺CD8⁺ cells from 2C_F1 mice that either rejected (left panels) or accepted (right panels) L^d+ skin allografts 120 days after transplantation were added into the MLR cultures as putative suppressor cells. The suppressor to responder cell ratios were 0:1, 10:1, 5:1, 2:1, and 1:1 as indicated. Cells were cultured in α-MEM supplemented with 10% FCS, 30 U/mL rIL-2 in the presence (top panels) or absence (bottom panels) of 50 U/mL rIL-4. Cell proliferation was measured by [³H] TdR incorporation after a 3.5-day culture. (□), S/R = 0:1; (▪), S/R = 10:1; (▤), S/R = 5:1; (▥), S/R = 2:1; (□), S/R = 1:1.