To further investigate the mechanism of IL-21-induced killing of MRSA, because IL-21 signals in part via STAT3, we next used neutrophils from patients with autosomal dominant hyper-IgE syndrome (AD-HIES) or Job’s syndrome, a disease caused by autosomal dominant mutations in STAT3 that result in STAT3 deficiency, with increased susceptibility to fungal and bacterial infections, including S. aureus (Freeman and Holland, 2008). This evidence concerns the gene IL21 and bacterial infectious disease.