Figure 2.

SAP-deficient CD8⁺ T cells secrete decreased IL-2 when activated by B cells and exogenous IL-2 rescues their defective proliferation. (A) Intracellular IL- 2 and (B) surface CD25 expression was monitored on WT and Sh2d1a^−/− (SAP^−/−) OT-I CD8⁺ T cells upon activation with OVA (10⁻⁸ M) and B cell- or B cell-depleted splenocyte-APCs for the indicated time. (C) WT and SAP^−/− OT-I CD8⁺ T cells were stimulated with Ag, B cell APCs and exogenous IL-2 and proliferation measured by [³H]-thymidine incorporation assays. (D) WT and SAP^−/− OT-I CD8⁺ T cells were stimulated as described in (C) except proliferation quantitated through CFSE dilution 4 d post-activation. Samples were collected for 1 min intervals and the maximum scale (y-axis) for each histogram is shown vertically at the top left of histograms. Error bars indicate ± SD and significance calculated using unpaired, two-tailed Student's t-tests with double (**) and triple asterisks (***) indicating p values of less than 0.01 and 0.001, respectively. The data are representative of three independent experiments.