IL17F encodes a pro-inflammatory cytokine that functions as an effector molecule in both innate and adaptive immune responses, playing crucial roles in antimicrobial host defense and tissue inflammation 1. IL17F signals through IL17RA-IL17RC heterodimeric receptor complexes or IL17RC homodimeric complexes, activating downstream NF-κB and MAPK pathways to induce expression of cytokines, chemokines, and antimicrobial peptides 2. The protein shares 50% sequence homology with IL17A and exhibits overlapping but non-redundant biological functions 3. IL17F is produced by various immune cell types including Th17 cells, γδ T cells, and innate lymphoid cells, with production occurring through both IL-23-dependent and IL-23-independent pathways 3. In disease contexts, IL17F contributes significantly to chr6 inflammatory conditions including psoriasis, psoriatic arthritis, and hidradenitis suppurativa 45. Preclinical studies demonstrate that IL17F induces qualitatively similar inflammatory responses to IL17A in skin and joint cells, and dual neutralization of both IL17A and IL17F provides more effective suppression of inflammatory responses than targeting IL17A alone 4. Clinical trials with bimekizumab, which blocks both IL17A and IL17F, show superior efficacy compared to IL17A-selective inhibitors in treating psoriasis, supporting IL17F's independent contribution to tissue inflammation 16.