Expression of perforin and Stx11 in FHL patients. (A) PBLs were stained with fluorochrome-conjugated anti-CD3, and anti-CD56 mAbs. Thereafter, cells were fixed, permeabilized, stained with antiperforin mAb, and analyzed by flow cytometry. Histograms depict perforin expression in CD3⁻CD56⁺ NK cells. (B) Quantification of perforin staining by flow cytometry. Values represent relative mean fluorescence of perforin in CD3⁻CD56⁺ NK cells as percent of adult control cells. The error bar indicates the SD of normalized perforin expression for 12 healthy controls. (C) Stx11 expression relative to actin control was measured by immunoblotting. Arrowheads indicate bands corresponding to actin and Stx11 immunoreactivity.