Diverse studies have shown the soluble forms of CTLA‐4 in human serum of autoimmune diseases.8 Although the biological significance of increased sCTLA‐4 serum levels has not been completely clarified, their possible pathogenetic role during autoimmune disorder can be explained in two ways: sCTLA‐4 inhibits the early T‐cell activation by recognizing CD80/CD86 and blocking the engagement of CD28 expressed on T cells. Here, CD28 is linked to autoimmune disease.