Our study, therefore, suggests a different involvement of BDNF in pSS and RA physiopathology, either by its role in the nervous system (39), where BDNF is involved in proliferation and survival of nervous tissue (40) or by its action on the immune system (41) where BDNF affects the proliferation of T- and B-lymphocytes (42, 43). This evidence concerns the gene BDNF and rheumatoid arthritis.