The increased frequency of IL-17-producing natural killer (NK) cells, CD4, and gamma-delta T cells in patients with ERA was also recently proposed to result from the expansion of intermediate CD14++CD16+ Mos due to their role as the major producer of IL-23, a key cytokine in the pathogenesis of ERA [26]. This evidence concerns the gene CD4 and enthesitis-related juvenile idiopathic arthritis.