β-agonist-induced PKA activity in type 2 T cells. VASP-Ser157 phosphorylation in CRTH2⁺ and CRTH2^- T cells or CD56⁺ and CD56^- T cells was detected in freshly isolated PBLs after 30 minutes' stimulation with vehicle, PGE₂ (1 μM), or ISO (10 μM), as described in “Materials and methods.” VASP-phospho-Ser157 expression is presented in histograms, analyzed in the indicated population within (A) CD161^- T cells and (B) CD5⁺ T cells. Background fluorescence from isotype control mAb was superimposable for all conditions (not shown). Direct comparisons between results in panels A and B cannot be made because amplification of the phospho-VASP signal was only performed in panel A, as explained in “Materials and methods.” (C, top) T cells from CD2^-/lo T-cell cultures were stimulated with PMA + calcimycin and analyzed for cytokine production (filled region, fluorescence from IL-13 staining; open region, background fluorescence from isotype control mAb). The preparation was more than 99% CD3⁺ and less than 5% IFN-γ⁺ (not shown). (C, bottom) In parallel, VASP-phospho-Ser157 was detected in this T-cell population after 30 minutes' stimulation with vehicle, ISO (10 μM), or db-cAMP (200 μM).