Impaired cytokine production by WASp-deficient Th2-primed effectors. WT and WAS^−/− naive CD4⁺ T cells were primed under Th2 conditions with plate-bound anti-TCRβ and anti-CD28 mAbs for 5 days. Cells were harvested and restimulated with plate-bound anti-TCRβ mAb. (A) ELISA from supernatants 24 hours after restimulation. (B) Th2-primed cells were restimulated with anti-TCRβ mAb for 24 hours, followed by intracellular cytokine staining. Numbers in quadrants equal the percentage of Th2-primed cells. (C) Kinetic analysis of CD4⁺ IL-4⁺ cells after restimulation using the CSA. *P ≤ .05 for differences between WT and WAS^−/− Th2-primed effectors across 3 independent experiments; paired Student t test. (D) Ex vivo memory cells (CD4⁺CD62L^lowCD44^high) were isolated from the spleens (SPNs) and LNs of unimmunized mice by FACS and restimulated using plate-bound anti-TCRβ mAb for 24 hours; cytokines in supernatants were assayed by ELISA. Results represent 1 of at least 3 comparable experiments. *P ≤ .05 for differences between WT and WAS^−/− Th2-primed effectors across 3 independent experiments; paired Student t test. Error bars indicate mean and SEM.