Interleukin 12 (IL-12) is an interleukin that is naturally produced by dendritic cells, macrophages, neutrophils, helper T cells and human B-lymphoblastoid cells (NC-37) in response to antigenic stimulation. IL-12 belongs to the family of interleukin-12. IL-12 family is unique in comprising the only heterodimeric cytokines, which includes IL-12, IL-23, IL-27 and IL-35. Despite sharing many structural features and molecular partners, they mediate surprisingly diverse functional effects.
The interleukin 4 is a cytokine that induces differentiation of naive helper T cells (Th0 cells) to Th2 cells. Upon activation by IL-4, Th2 cells subsequently produce additional IL-4 in a positive feedback loop. IL-4 is produced primarily by mast cells, Th2 cells, eosinophils and basophils. It is closely related and has functions similar to IL-13.
Interleukin-15 (IL-15) is a protein that in humans is encoded by the IL15 gene. IL-15 is an inflammatory cytokine with structural similarity to Interleukin-2 (IL-2). Like IL-2, IL-15 binds to and signals through a complex composed of IL-2/IL-15 receptor beta chain (CD122) and the common gamma chain. IL-15 is secreted by mononuclear phagocytes following infection by virus(es). This cytokine induces the proliferation of natural killer cells, i.e. cells of the innate immune system whose principal role is to kill virally infected cells.
Interleukin-18 (IL-18), also known as interferon-gamma inducing factor is a protein which in humans is encoded by the IL18 gene. The protein encoded by this gene is a proinflammatory cytokine. Many cell types, both hematopoietic cells and non-hematopoietic cells, have the potential to produce IL-18. It was first described in 1989 as a factor that induced interferon-γ (IFN-γ) production in mouse spleen cells. Originally, IL-18 production was recognized in Kupffer cells, and liver-resident macrophages. However, IL-18 is constitutively expressed in non-hematopoietic cells, such as intestinal epithelial cells, keratinocytes, and endothelial cells. IL-18 can modulate both innate and adaptive immunity and its dysregulation can cause autoimmune or inflammatory diseases.
Interleukin-31 (IL-31) is a protein that in humans is encoded by the IL31 gene that resides on chromosome 12. IL-31 is an inflammatory cytokine that helps trigger cell-mediated immunity against pathogens. It has also been identified as a major player in a number of chronic inflammatory diseases, including atopic dermatitis.
Interleukin 30 (IL-30) forms one chain of the heterodimeric cytokine called interleukin 27 (IL-27), thus it is also called IL27-p28. IL-27 is composed of α chain p28 and β chain Epstain-Barr induce gene-3 (EBI3). The p28 subunit, or IL-30, has an important role as a part of IL-27, but it can be secreted as a separate monomer and has its own functions in the absence of EBI3. The discovery of IL-30 as individual cytokine is relatively new and thus its role in the modulation of the immune response is not fully understood.
Interleukin-29 (IL-29) is a cytokine and it belongs to type III interferons group, also termed interferons λ (IFN-λ). IL-29 plays an important role in the immune response against pathogenes and especially against viruses by mechanisms similar to type I interferons, but targeting primarily cells of epithelial origin and hepatocytes.
Interleukin-25 (IL-25) – also known as interleukin-17E (IL-17E) – is a protein that in humans is encoded by the IL25 gene on chromosome 14. IL-25 was discovered in 2001 and is made up of 177 amino acids.
Interleukin 24 (IL-24) is a protein in the interleukin family, a type of cytokine signaling molecule in the immune system. In humans, this protein is encoded by the IL24 gene.
Interleukin-22 (IL-22) is a protein that in humans is encoded by the IL22 gene.
The type III interferon group is a group of anti-viral cytokines, that consists of four IFN-λ (lambda) molecules called IFN-λ1, IFN-λ2, IFN-λ3, and IFN-λ4. They were discovered in 2003. Their function is similar to that of type I interferons, but is less intense and serves mostly as a first-line defense against viruses in the epithelium.
Interleukin-22 receptor subunit alpha-2 (IL-22RA2), also known as interleukin-22 binding protein (IL-22BP) is a naturally secreted monomeric protein acting as an interleukin-22 (IL-22) antagonist with inhibitory effects on IL-22 activity in vivo. IL-22BP is in humans encoded by the IL22RA2 gene located on chromosome 6, and in mice is encoded by the il22ra2 gene located on chromosome 10. IL-22BP belongs to the class II cytokine receptor family and it is a soluble receptor homolog of IL-22R.
The interleukin 4 receptor is a type I cytokine receptor. It is a heterodimer, that is, composed of two subunits. IL4R is the human gene coding for IL-4Rα, the subunit which combines with either common gamma chain or with IL-13Rα1.
Interleukin 20 receptor, alpha subunit, is a subunit of the interleukin-20 receptor, the interleukin-26 receptor, and the interleukin-24 receptor. The interleukin 20 receptor, alpha subunit is also referred to as IL20R1 or IL20RA. The IL20RA receptor is involved in both pro-inflammatory and anti-inflammatory responses, signaling through the JAK-STAT pathway.
The interleukin-23 receptor is a type I cytokine receptor. It is encoded in human by the IL23R gene. In complex with the interleukin-12 receptor β1 subunit (IL-12Rβ1), it is activated by the cytokine interleukin 23 (IL-23). The IL23R mRNA is 2.8 kilobases in length and includes 12 exons. The translated protein contains 629 amino acids; it is a type I penetrating protein and includes a signal peptide, an N-terminal fibronectin III-like domain and an intracellular part that contains three potential tyrosine phosphorylation domains. There are 24 IL23R splice variants in mitogen-activated lymphocytes. IL23R includes some single-nucleotide polymorphisms in the region encoding the domain that binds IL-23, which may lead to differences between people in Th17 activation. There is also a variant of IL-23R that consists of just the extracellular part and is known as soluble IL-23R. This form can compete with the membrane-bound form to bind IL-23, modulating the Th17 immune response and regulation of inflammation and immune function.
Interleukin-10 receptor (IL-10R) is a type II cytokine receptor. The receptor is tetrameric, composed of 2α and 2β subunits. The α subunit is expressed on haematopoietic cells whilst the β subunit is expressed ubiquitously. The α subunit is exclusive to interleukin-10, however the β subunit is shared with other type II cytokine receptors such as IL-22R, IL-26R and INFλR.
Interleukin 20 receptors (IL20R) belong to the IL-10 family. IL20R are involved in both pro-inflammatory and anti-inflammatory immune response. There are two types of IL20R: Type I and Type II.
Interleukin-28 receptor is a type II cytokine receptor found largely in epithelial cells. It binds type 3 interferons, interleukin-28 A, Interleukin-28B, interleukin 29 and interferon lambda 4. It consists of an α chain and shares a common β subunit with the interleukin-10 receptor. Binding to the interleukin-28 receptor, which is restricted to select cell types, is important for fighting infection. Binding of the type 3 interferons to the receptor results in activation of the JAK/STAT signaling pathway.
The Interleukin-2 receptor alpha chain is a protein involved in the assembly of the high-affinity Interleukin-2 receptor, consisting of alpha (IL2RA), beta (IL2RB) and the common gamma chain (IL2RG). As the name indicates, this receptor interacts with Interleukin-2, a pleiotropic cytokine which plays an important role in immune homeostasis.
Interleukin 23 (IL-23) is a heterodimeric cytokine composed of an IL-12B (IL-12p40) subunit and an IL-23A (IL-23p19) subunit. IL-23 is part of the IL-12 family of cytokines. The functional receptor for IL-23 consists of a heterodimer between IL-12Rβ1 and IL-23R.
