CD4 and systemic lupus erythematosus: The analysis of BLyS receptors’ expression on the surface of T-cell subsets and peripheral blood monocytes from SLE patients at baseline revealed the presence of BAFF-R, BCMA, and TACI at a rather low rate on CD4+ and CD8+ T cells, while CD14+ cells firmly expressed only BAFF-R (Figure 6A–C).