Perforin expression in adult and cord blood NK cells and T cells. Cells from adult peripheral and cord blood donors were stained with fluorochrome-conjugated anti-CD3 and -CD56 mAbs, followed by fixation, permeabilization, and intracellular staining with antiperforin mAb. Lymphocytes were gated on forward scatter/side scatter plots, followed by gating on CD3⁺ and CD3⁻ cells. Profiles show (A) CD56 versus perforin mAb staining of CD3⁺ T cells and (B) CD56 versus perforin mAb staining of CD3⁻ cells.