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CD278

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ICOS
Identifiers
AliasesICOS, AILIM, CD278, CVID1, inducible T-cell co-stimulator, inducible T-cell costimulator, inducible T cell costimulator
External IDsOMIM: 604558; MGI: 1858745; HomoloGene: 8097; GeneCards: ICOS; OMA:ICOS - orthologs
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_012092

NM_017480

RefSeq (protein)

NP_036224

NP_059508

Location (UCSC)Chr 2: 203.94 – 203.96 MbChr 1: 61.02 – 61.04 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Inducible T-cell costimulator (also called CD278) is an immune checkpoint protein that in humans is encoded by the ICOS (Inducible T-cell COStimulator) gene.[5][6][7] [8][9] The protein belongs to the CD28 and CTLA-4 cell-surface receptor family. These are proteins expressed on the surface of immune cells that mediate signalling between them. A surface protein, the ligand, binds specifically to its receptor on another cell, leading to a signalling cascade in that cell.

Function

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ICOS is a receptor protein expressed on the surface of activated T cells. Its ligand ICOS-L (previously called B7RP-1) is constitutively expressed on B cells. Stimulation of the ICOS receptor on T cells by ICOS-L on B cells is required for the development of follicular helper T (Tfh) cells. [10] ICOS forms homodimers and plays an important role in cell-cell signaling, immune responses and regulation of cell proliferation.[7]

Knockout phenotype

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Compared to wild-type naïve T cells, ICOS-/- T cells activated with plate-bound anti-CD3 have reduced proliferation and IL-2 secretion.[11] The defect in proliferation can be rescued by addition of IL-2 to the culture, suggesting the proliferative defect is due either to ICOS-mediated IL-2 secretion or the activation of similar signaling pathways between ICOS and IL-2. In terms of Th1 and Th2 cytokine secretion, ICOS-/- CD4+ T cell activated in vitro reduced IL-4 secretion, while maintaining similar IFN-g secretion. Similarly, CD4+ T cells purified from ICOS-/- mice immunized with the protein keyhole limpet hemocyanin (KLH) in alum or complete Freund's Adjuvant have attenuated IL-4 secretion, but similar IFN-g and IL-5 secretion when recalled with KLH.

These data are similar to an airway hypersensitivity model showing similar IL-5 secretion, but reduced IL-4 secretion in response to sensitization with Ova protein, indicating a defect in Th2 cytokine secretion, but not a defect in Th1 differentiation as both IL-4 and IL-5 are Th2-associated cytokines. In agreement with reduced Th2 responses, ICOS-/- mice expressed reduced germinal center formation and IgG1 and IgE antibody titers in response to immunization.

Combination therapy

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Ipilimumab patients expressed increased ICOS+ T cells in tumor tissues and blood. The increase served as a pharmacodynamic biomarker of anti-CTLA-4 treatment. In wild-type C57BL/6 mice, anti-CTLA-4 treatment resulted in tumor rejection in 80 to 90% of subjects, but in gene-targeted mice that were deficient for either ICOS or its ligand (ICOSLG), the efficacy was less than 50%. An agonistic stimulus for the ICOS pathway during anti-CTLA-4 therapy resulted in an increase in efficacy that was about four to five times as large as that of control treatments. This combination therapy incorporating ICOS costimulation and CTLA-4 blockade effectively remodels tumor-associated macrophages (TAMs) towards an antitumor phenotype, demonstrating promising therapeutic potential in cancer treatment.[12] As of 2015 antibodies for ICOS were not available for clinical testing.[13]

References

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  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000163600Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000026009Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ Hutloff A, Dittrich AM, Beier KC, Eljaschewitsch B, Kraft R, Anagnostopoulos I, et al. (Jan 1999). "ICOS is an inducible T-cell co-stimulator structurally and functionally related to CD28". Nature. 397 (6716): 263–6. Bibcode:1999Natur.397..263H. doi:10.1038/16717. PMID 9930702. S2CID 4415254.
  6. ^ Yoshinaga SK, Whoriskey JS, Khare SD, Sarmiento U, Guo J, Horan T, et al. (Dec 1999). "T-cell co-stimulation through B7RP-1 and ICOS". Nature. 402 (6763): 827–32. Bibcode:1999Natur.402..827Y. doi:10.1038/45582. PMID 10617205. S2CID 4360410.
  7. ^ a b "Entrez Gene: ICOS inducible T-cell co-stimulator".
  8. ^ Rudd CE, Schneider H (Jul 2003). "Unifying concepts in CD28, ICOS and CTLA4 co-receptor signalling". Nature Reviews. Immunology. 3 (7): 544–56. doi:10.1038/nri1131. PMID 12876557. S2CID 19833513.
  9. ^ Dong C, Juedes AE, Temann UA, Shresta S, Allison JP, Ruddle NH, et al. (Jan 2001). "ICOS co-stimulatory receptor is essential for T-cell activation and function". Nature. 409 (6816): 97–101. Bibcode:2001Natur.409...97D. doi:10.1038/35051100. PMID 11343121. S2CID 11891841.
  10. ^ Akiba H, Takeda K, Kojima Y, Usui Y, Harada N, Yamazaki T, et al. (August 2005). "The role of ICOS in the CXCR5+ follicular B helper T cell maintenance in vivo". Journal of Immunology. 175 (4): 2340–2348. doi:10.4049/jimmunol.175.4.2340. PMID 16081804.
  11. ^ Brennan FR (2014). "T Cell Inhibitors in Phase 1 and 2 Clinical Studies for Immunological Disorders". In Dübel S, Reichert JM (eds.). Handbook of Therapeutic Antibodies (2nd ed.). Weinheim, Bergstr: Wiley-VCH. pp. 1088–9. ISBN 978-3-527-32937-3.
  12. ^ Sharma N, Fan X, Atolagbe OT, Ge Z, Dao KN, Sharma P, et al. (April 2024). "ICOS costimulation in combination with CTLA-4 blockade remodels tumor-associated macrophages toward an antitumor phenotype". The Journal of Experimental Medicine. 221 (4). doi:10.1084/jem.20231263. PMC 10959121. PMID 38517331.
  13. ^ Sharma P, Allison JP (Apr 2015). "The future of immune checkpoint therapy". Science. 348 (6230): 56–61. Bibcode:2015Sci...348...56S. doi:10.1126/science.aaa8172. PMID 25838373. S2CID 4608450.

Further reading

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This article incorporates text from the United States National Library of Medicine, which is in the public domain.