IL4 and Arthritis: Besides, XBP1 was indispensable in the Th2 lineage commitment for its involvement in Th2 polarization,173, 174 considering Th2 as source of IL‐4 and IL‐13 which show significant role in arthritis,175 the immune effect of IRE1α pathway in T cells can also be a therapeutical target for arthritis treatment and prevention.