IL17A and rheumatoid arthritis: However, another study from Norway [18] suggested an association between the 197A genotype and resistance to developing rheumatoid arthritis Since many studies have demonstrated higher levels of IL-17 in patients with rheumatoid arthritis and the essential roles of IL-17 in mediating joint damage [45], [46], [47], the G197A SNP might affect the initiation of rheumatoid arthritis, but not disease progression and severity.