CD19 and pemphigus: Coincidentally, Zhang et al. found that RSAD2 was increased in CD19 + B cells of patients with systemic autoimmune diseases such as pemphigus and systemic lupus erythematosus15, 16, 17 In addition, RSAD2 is highly expressed in CD4 + T cells of patients with rheumatoid arthritis, and its expression is significantly correlated with the clinical characteristics of the disease.13, 26