IL17A (Interleukin 17A), also referred to IL17 or CTLA8 (Cytotoxic T-lymphocyte-associated serine esterase 8), is a 17.5 kDa glycoprotein encoded in humans by the IL17A gene that is located at the chromosome 6p12.2. It is composed of 155 amino acids and belongs to the IL17 protein family (IL17A- IL17F), of which each monomer contains four highly conserved cysteine residues. IL17A is a proinflammatory cytokine released by CD4+ T cells (Th17 cells), CD8+ T cells (Tc17 cells), invariant natural killer T cells (iNKT cells), γδ T cells and innate lymphoid cells (ILCs). This cytokine functions in the regulation of activities of NF-kappaB and mitogen-activated protein kinases. Its high levels are associated with several chronic inflammatory diseases such as psoriasis, rheumatoid arthritis, and multiple sclerosis.. IL23 (Interleukin-23) is a dimeric cytokine and belongs to the IL-12 family of cytokines. This family is a part of the IL-6 superfamily that composed of four heterodimeric cytokines sharing sequence homology. IL-23 consists of the two disulfide-linked subunits p19 (IL-23p19) and p40 (IL-23p40), which is closely related to IL-12, made up of a common p40 subunit and a distinct p35 polypeptide. IL-23 and IL-12 are secreted by innate immune cells and regulate the development of adaptive immunity. Cytokine IL-23 has immunoregulatory and proinflammatory roles and is expressed primarily by the macrophages and dendritic cells (DCs). Its main biological effects are stimulation of antigen presentation by DCs, production of interferon-γ (IFN-γ), and T cell differentiation to T-helper 17 (Th17) cells.