SAA1 and rheumatoid arthritis: Other highly upregulated genes in EED include serum amyloid A1 and A2 (SAA1) and (SAA2), which encode acute phase proinflammatory and chemotactic proteins, IL21, which encodes a potent cytokine regulator of immune cells, including T follicular helper cells, and IL17A, which encodes an inflammatory cytokine that can mediate protective innate immunity to pathogens or contribute to the pathogenesis of inflammatory diseases, such as psoriasis and rheumatoid arthritis.