CD4 and rheumatoid arthritis: In addition, there were no significant differences between SE-HD and SE + HD in HLA-DR expression on B cells or CXCR4 expression on memory CD4+ T cells (Figures S3 and S5), which suggests that the relationship between SE and enhanced HLA-DR expression on B cells or enhanced CXCR4 expression on memory CD4+ T cells could be specific to RA.