IL21 and autoimmune disease: In other words, changes in CD4+ T cells affect not only the secretion of cytokines such as IL-17, IL-6, and IL-21, but also the function of CD8+ T cells, and, in combination with changes in the number of CD4+ T cells in the lesions of KFD, may be one of the reasons for the possibility of developing into autoimmune diseases like SLE.