MOLECULES

Full name: Interleukin-17A

Aliases: IL17, CTLA8, IL-17, CTLA-8, and IL-17A¹

Size: 35 kDa²

Family: IL-17 family (IL-17A, IL-17B, IL-17C, IL-17D, IL-17E, and IL-17F)³

Receptors: IL-17RA (= IL-17R)²

Major cellular sources: Activated Th17 cells, CD8+ T cells, γ𝛿 T cells, NK cells, NKT cells, neutrophils and ILCs²

Major cellular targets: Epithelial/endothelial cells, fibroblasts, osteoblasts, monocytes, macrophages, B cells, T cells myelomonocytic cells and marrow stromal cells, and chondrocytes^2,3

Disease states associated with: Rheumatoid arthritis, multiple sclerosis, psoriasis, inflammatory bowel disease, allergic asthma, atopic dermatitis, contact hypersensitivity, and graft-versus-host-disease²

Major physiologic functions:

• IL-17A acts mainly on non-hematopoietic cells, particularly epithelial cells, and plays an active role in maintaining immunity at boundary tissues.³
• IL-17A acts on a variety of cells, which respond by upregulating the expression of pro-inflammatory cytokines, chemokines, metalloproteases, antimicrobial peptides, and remodeling proteins.^1-3
• By inducing cells to produce chemokines, IL-17A attracts neutrophils to mediate defense against different pathogens.²
• IL-17A directly contributes to leukocyte migration and tissue remodeling by promoting the secretion of metalloproteases.³
• IL-17A also regulates the activities of NF- B and mitogen-activated protein kinases and can stimulate the expression of IL-6 and cyclooxygenase-2 (PTGS2/COX-2), as well as enhance the production of nitric oxide.¹

CD: cluster of differentiation; CTLA: cytotoxic T-lymphocyte associated antigen; IL: interleukin; IL-17R: IL-17 receptor; ILC: innate lymphoid cell; NK: natural killer; NF- B: nuclear factor-kappa B; NKT: natural killer T; Th: T helper.