TNF and enthesitis: Given the neutralizing effect of PGRN Abs on PGRN plasma levels in PsA patients (Figure 3), as well as in other autoimmune diseases [8], and, more important, given the results of the functional in vitro assays indicating a sensitizing effect of PGRN Abs for the effects of TNF-α in patients with PsA, a higher prevalence of PGRN Abs in patients with TNF-α-induced disease manifestations such as enthesitis and dactylitis could obviously be expected.