 Among IL-17 family members, the IL-17F isoforms 1 and 2 (ML-1) have the highest sequence homology with IL-17A (55 and 40%, respectively).They follow by IL-17B, which has 29% similarity to IL-17A, IL-17D (25%), IL-17C (23%), and IL-17E (17%).In mammals, the sequences of these cytokines are highly conserved.