For instance, one study reported that serum CXCL12 levels were significantly elevated in SLE patients (Robak et al., 2007), while the expression of CXCR4 on peripheral B cells and CD4+ T cells was also markedly upregulated and correlated with disease activity (Wang et al., 2010). This evidence concerns the gene CXCL12 and systemic lupus erythematosus.