(A) Flow cytometry quantification of NK cells per milliliter in peripheral blood of XLPDR patients (P1–P5) and unaffected individuals (UA4–UA11). Horizontal bars represent the mean; error bars represent the SD. *P < 0.015, Student’s 2-tailed t test. Data are the aggregate from up to 3 independent measurements. (B) Flow cytometry quantification of NK cells in peripheral blood as a percentage of total lymphocytes. P1–P5 and UA1–UA12 are represented. Horizontal bars represent the mean; error bars represent the SD. *P < 0.0005, Student’s 2-tailed t test. Data are the aggregate of 7 independent measurements spanning up to 8 years. (C) NK cell direct cytotoxicity against 721.221 target cells was assessed using NK cells from unaffected controls (UA1, UA2, UA13) or XLDPR patients (P1 and P2), using effector/target (E/T) ratios of 1 and 5. Bars represent the mean; error bars represent the SEM. *P < 0.0065, and **P < 0.0001 by 2-way ANOVA. Data are the aggregate of 2 independent experiments. (D) NK cell direct cytotoxicity against the 721.221 target cell line was determined over the indicated E/T ratios. Primary NK cells obtained from 5 healthy donors (UA14–UA18) were subjected to POLA1 silencing using 2 siRNA duplexes or a pool of them. The data are representative of 2 independent experiments; error bars represent the SEM. *P < 0.0001 by 2-factor ANOVA comparing siPOLA1 samples against controls. Data are the aggregate of 5 independent experiments. (E) Same as D but using the tumor-derived NK cell line NK92mi. The data are representative of 3 independent experiments; error bars represent the SEM. *P < 0.0001 by 2-way ANOVA comparing siPOLA1 mix against control samples. Data are representative of 2 independent experiments. (F) Antibody-dependent cell cytotoxicity (ADCC) of NK cells from unaffected controls (UA8–UA10) and XLPDR patients (P1 and P2). SKOV-3 ovarian cancer cells treated with anti–human epidermal growth factor receptor 2 (anti-HER2) antibodies were used as the target cell line; cells incubated with control antibody (IgG) were used as a negative control. Bars represent the mean; error bars represent the SEM. NS, nonsignificant; P > 0.1 by 2-factor ANOVA comparing UA to XLPDR groups. Data are from a single experiment.