Peptides carrying PDK1 Thr-513 influence TCR-CD28-mediated mouse primary CD4+ T-cell activation. A, Uptake of PTD-conjugated peptides was analyzed by flow cytometry with FITC-conjugated peptides. B, Localization of PTD-conjugated peptides was analyzed by fluorescence microscopy with FITC-conjugated peptides. C and D, CD4+ T cells were isolated from C57BL6 mice and activated with anti-CD3 and anti-CD28 antibodies for the indicated times. Cells were stained with fluorochrome-conjugated anti-CD4, anti-CD69, and anti-CD25 antibodies. Surface expression of CD69 (C) and CD25 (D) on CD4+ T cells was analyzed by flow cytometry.