IL21 and viral infectious disease: Furthermore, elevated IL-21 production has been reported in patients across a wide range of autoimmune conditions with dysregulated humoral immunity, including type 1 diabetes, rheumatoid arthritis, and systemic lupus erythematosus (Kenefeck et al., 2015; Ferreira et al., 2015; Dolff et al., 2011; Terrier et al., 2012; Niu et al., 2010; Liu et al., 2012), and IL-21 has been shown to influence the course of adaptive immune responses to viral infections (Elsaesser et al., 2009; Collins and Speck, 2015).