CD4 and pemphigus: Since CD4+ T cells in patients possessed an activated phenotype with dramatic increase of CD69 expression, which was strongly and positively correlated with CD19hi B cell frequency (Supplementary Fig. 1), we further investigated the possibility whether higher percentages of CD19hi B cells in the periphery of SLE and pemphigus patients (Fig. 1) were derived from the help of activated CD4+ T cells under the pathology.