Moreover, stimulation of D1DR in vitro with the specific agonist A6893043, in combination with CpG ODN 2006 (shortly CpG), a TLR9 ligand and thus B cell-stimulus, significantly increased B cell proliferation only in female RA patients but no significant differences were observed in HC (Fig. 4d) and in men (Suppl. This evidence concerns the gene TLR9 and rheumatoid arthritis.