CD4 and systemic lupus erythematosus: Moreover, compared with control MDSCs, lupus MDSCs significantly promoted the activation of splenic B cells (Supplementary Fig. 1A, B) and CD4+ T cells (Supplementary Fig. 1C, D), and increased the percentage of germinal center B cells (Supplementary Fig. 1E, F) and plasmacytes (Supplementary Fig. 1G, H) in the spleen.