Although cumulative evidence has implicated the broad pathophysiologic profile of TSLP in inflammatory and autoimmune diseases such as RA (18–21), this is the first study to investigate whether the existence of two isoforms of TSLP, referred to as lTSLP and sTSLP, is distinctly expressed in the pathophysiology of RA and whether their expression is correlated with disease activity in RA. Here, TSLP is linked to autoimmune disease.