The first indication of a potential involvement of IL-21 in autoimmunity was the finding that IL-21 was overexpressed in several strains of mice (e.g., BXSB-Yaa, B6.Sle1-Yaa, Sanroque, MRL/MpJ-FASlpr/lpr/J) that develop lupus-like disease (86, 124, 125). Here, IL21 is linked to Autoimmunity.