For example, in vivo data show that blockade of IL-21 signaling using an IL-21 receptor Fc fusion protein (IL-21R Fc) decreases the disease severity in several murine models including collagen-induced arthritis [8], the MRL-Faslpr lupus model [9] and the diabetic NOD model [10]. This evidence concerns the gene IL21R and systemic lupus erythematosus.