STAT3 activation enhances NK-cell degranulation and cytotoxicity. Primary human NK cells were treated with 20 ng/mL of IL10 or IL21 with or without 0.1 µM of JSI-124 for 24 hours, and followed by coincubation with K562 cells for 4 hours. Target-mediated NK-cell degranulation was assessed by flow cytometry for CD107a. (A) Representative dot plot; (B) Pooled data from 3 donors. P values are shown for 2-tailed unpaired Student t tests.