Figure 1.

Bi-allelic mutations in STXBP2 impair natural killer (NK) degranulation and cytotoxicity, which is partially restored by IL-2. Peripheral blood mononuclear cells (PBMCs) were isolated from a healthy donor control (Control) and an FHL5 patient and incubated for 16 h in the absence (-IL-2) or presence (+IL-2) of 100 U/mL of human IL-2. (A) PBMCs were incubated for 3 h in the absence (−K562) or presence (+ K652) of K562 target cells. NK degranulation was assessed by measurement of CD107a surface labeling in the CD16+ cell populations. Data are representative of two independent experiments. (B,C) PBMCs taken during therapy (B) or after therapy (C) were incubated with ⁵¹Cr-labeled K562 target cells for 4 h at the indicated effector to target cell ratios (normalized for the% of NK cells). NK cytotoxicity was determined by the release of ⁵¹Cr from target cells. Data are representative of two independent experiments.