Because TNF inhibitors cannot cross the blood brain barrier, a paradoxical increase in TNF within the CNS may occur.43 Induction of autoimmunity also has been proposed by inhibiting the TNF promotion of T-regulatory cell survival and proliferation.44 In this study, we were unable to ascertain whether this association indicates de novo inflammation or exacerbation of already aberrant inflammatory pathways in patients with these autoimmune diseases. This evidence concerns the gene TNF and autoimmune disease.