“…For example, individuals with Th1 deficiency are predisposed to recurrent bacterial and mycobacterial infections, and individuals with Th17 deficiency are predisposed to chronic mucocandidiasis ( McDonald, 2012 ; Cook and Tangye, 2009 ; Hernández-Santos et al, 2013 ). In contrast, systemic autoimmunity is more common in individuals with Th17 overactivity and/or regulatory T-cell (Treg) deficiency ( Osnes et al, 2013 ; Costa et al, 2017 ; Bonelli et al, 2008 ; Miyara et al, 2005 ), and allergy is more common in individuals with a similar imbalance between Th2 cells and Tregs ( Bacher and Scheffold, 2018 ; McGee and Agrawal, 2006 ; Finotto, 2008 ). Pathogenic and protective roles have also been described for Th9 and Th22 cells in the context of inflammatory skin diseases and various autoimmune conditions, including type I diabetes ( Ryba-Stanisławowska et al, 2016 ) and multiple sclerosis ( Rolla et al, 2014 ).…”