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Gene

ICOS

inducible T cell costimulator

Summary

Cytogenetic location
2q33.2
Coordinates
Chromosome 2: 203,936,763–203,961,577 (GRCh38)
Exons
5 exons across 24.8 kb
Protein
199 amino acids
Also known as
AILIM, CD278
MANE Select transcript
ENST00000316386.11NM_012092.4
Locus type
gene with protein product
  • Very high
  • Confident
  • Low
  • Very low

Reference genomeGRCh38

Positions on gene and variant pages follow this choice, in this browser.

Curated reports relevant to this gene

  • Common Variable Immunodeficiency (Monogenic CVID)

    • Common variable immunodeficiency

      Low IgG with low IgA and/or IgM and poor vaccine responses; single-gene forms include NFKB1, NFKB2, ICOS, CD19, CD81, CR2, IKZF1, IRF2BP2, SEC61A1 and TNFRSF13B (TACI).

      • ClinGen rates the link definitive
      • 1 GenCC submitter rates it definitive or strong
      What knowing changes

      Immunoglobulin replacement and early treatment of infections are standard; a genetic cause can guide monitoring for autoimmunity, lymphoma and lung disease, and some forms (such as LRBA deficiency) respond to targeted therapy.

Broader groupings

  • Other Inborn Errors of Immunity

    • Inborn error of immunity

      One of 114 genes linked to it

      Inherited disorders of the immune system caused by changes in single genes, affecting how the body fights infection or regulates inflammation.

      • ClinGen rates the link definitive
      • 1 GenCC submitter rates it definitive or strong
    • Immunodeficiency Disease

      One of 170 genes linked to it

      Disease in which there is a deficiency or defect in the mechanisms of immunity, either cellular or humoral.

      • ClinGen rates the link definitive
      • 1 GenCC submitter rates it definitive or strong
      What knowing changes

      HSCT for SCID and severe PIDs; immunoglobulin replacement (IVIG/SCIG) for antibody deficiencies; leniolisib (Joenja, FDA 2023) for APDS; gene therapy for ADA-SCID; abatacept for CTLA4/LRBA deficiency; prophylactic antibiotics; G-CSF for CGD

How ICOS is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Known disease-causing sites
  • Stretches short reads find hard
Chromosome 2, with a bracket where ICOS sits. ICOS and 3 genes near it on chromosome 2, from 203,449,170 to 204,449,169.Chromosome 22q33.2p25.3p25.2p25.1p24.3p24.2p24.1p23.3p23.2p23.1p22.3p22.2p22.1p21p16.3p16.2p16.1p15p14p13.3p13.2p13.1p12p11.2p11.1q11.1q11.2q12.1q12.2q12.3q13q14.1q14.2q14.3q21.1q21.2q21.3q22.1q22.2q22.3q23.1q23.2q23.3q24.1q24.2q24.3q31.1q31.2q31.3q32.1q32.2q32.3q33.1q33.2q33.3q34q35q36.1q36.2q36.3q37.1q37.2q37.3203.6 Mb203.8 Mb204 Mb204.2 Mb204.4 MbRAPH1: 203,394,345–203,535,478, reverse strandRAPH1CD28: 203,706,517–203,739,756, forward strandCD28CTLA4: 203,853,888–203,873,965, forward strandCTLA4ICOS: 203,936,763–203,961,577, forward strandICOSDiagram of ICOS: 5 exons on the forward strand of chromosome 2Exon 1: 1 known disease-causing siteExon 2: 10 known disease-causing sitesExon 1: 203,936,763–203,936,872, 110 basesExon 2: 203,955,636–203,955,971, 336 basesExon 3: 203,956,659–203,956,765, 107 basesExon 4: 203,957,799–203,957,883, 85 basesExon 5: 203,959,586–203,961,577, 1,992 bases123455′3′

Exons of the gene's MANE Select transcript (release v1.5), from NCBI and EMBL-EBI, on the GRCh38 reference genome.

Chromosome bands from UCSC's GRCh38 ideogram (2022-10-29).

Nearby genes from Ensembl release 116, on GRCh38.

Exons make up 2.6 kb of the gene's 24.8 kb; 600 of those bases code for the protein.

How a genome test reads ICOS

13

positions in ICOS where ClinVar classes a change as pathogenic or likely pathogenic

None of them falls in a region short reads find hard.

A whole genome covers all 24.8 kb of ICOS, introns included, not only the 2.6 kb of exons.

Where this comes from

  • HGNC: the gene's symbol, name, other symbols and location.
  • MANE Select v1.5, from NCBI and EMBL-EBI: the transcript, its exons and coding sequence.
  • GenCC and ClinGen, released 2026-10-16: which conditions the gene is linked to, and how strongly.
  • The ACMG secondary findings list, SF v3.2.
  • ClinVar and the GIAB stratifications: known disease-causing sites, and the regions short reads find hard.
  • The Human Phenotype Ontology, release 2026-09-01: the traits linked to the gene. Find out more at hpo.jax.org.
  • Data release 2026.10.16-c6eea6bf.

Cite this page

APA

Dante Labs. (n.d.). ICOS gene: inducible T cell costimulator. Retrieved 17 October 2026, from https://dantelabs.com/genes/icos

Vancouver

Dante Labs. ICOS gene: inducible T cell costimulator [Internet]. [cited 17 October 2026]. Available from: https://dantelabs.com/genes/icos

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