Since JAK3 is always paired with JAK1 and is solely associated with the γc cytokine receptor whose activation is associated with inflammation in addition to lymphoid development and homeostasis (Fig. 2), it was hypothesized that partial JAK1/JAK3 inhibition might be anti-inflammatory without being markedly immunosuppressive, prompting investigators to seek indications among the autoimmune diseases. Here, JAK3 is linked to autoimmune disease.