IL17A and rheumatoid arthritis: Therefore, and given that interferon (IFN)-γ (a Th1 product) and interleukin(IL)-17 (a Th17 product) are elevated in RA, the association with the HLA-DRB1*SE suggests that in RA, HLA-DRB1*SE alleles present an arthritogenic peptide to T cells to initiate an immune response that culminates in a cytokine cascade with IFN-γ, IL-17, tumor necrosis factor (TNF)-α and IL-6 [19, 20].