Unimpaired TCR-mediated early T-cell activation in mice lacking H-ras or N-ras. (A) Splenocytes from WT, H-ras–, and N-ras–deficient mice were stimulated without or with anti-CD3 plus anti-CD28 mAb for 48 hours and stained for CD25 and CD69 expression. Numbers indicate percentage of cells in the gated region. (B) IL-2 production by splenic T cells stimulated with anti-CD3 (solid line), concanavalin A (dotted line), or without stimulation (shaded curve), as measured after 48 hours by fluorescent bead assay. Numbers over each curve indicate IL-2 concentration (ng/mL). (C) Proliferation responses of unstimulated and anti–CD3/CD28-stimulated LN T cells. Mean [³H]-thymidine incorporation ± SD of triplicate cultures is shown (*P < .05 vs WT). Results in each panel are representative of ≥ 2 independent experiments.