Impaired degranulation and cytotoxicity by resting NK cells from GS2 patients. (A) Resting PBMCs from healthy adult and infant donors plus GS2 and FHL3 patients were evaluated for cytotoxicity toward K562 cells in a 4-hour ⁵¹Cr-release assay. Lytic units (LU) at 25% target cell lysis were calculated from specific lysis values. Each point represents 1 person, with lines indicating mean values. (B) Resting PBMCs were incubated alone or with target cells as indicated for 2 hours at 37°C. Thereafter, cells were stained with fluorochrome-conjugated anti-CD3, anti-CD56, and anti-CD107a mAbs. Lymphocytes were gated on forward/side scatter plots, followed by gating on CD3 versus CD56 plots. Induced CD107a surface expression on CD3⁻CD56⁺ NK cells after indicated stimulation was plotted. Plus symbols represent mean values; error bars, SD. Boxes represent 25th, 50th, and 75th percentiles. For patient groups, each point represents 1 person, with lines indicating mean values.