Full name: Inducible T-cell costimulator ligand

Aliases:1 ICOSLG, B7H, B7H2, GL50, B7-H2, B7RP1, CD275, ICOSL, LICOS, and B7RP-1

Family:2,3 B7 family member

Receptors:3,4 T-cell–specific cell surface receptor

Major cellular sources:2-6 B cells, monocytes, macrophages, DCs, nonlymphoid cells

Major cellular targets:4 Tfh cell

Disease states associated with:6 Systemic lupus erythematosus

Major physiologic functions:

  • ICOS-L binds to ICOS exclusively and activates a cascade of signal transduction pathways that inhibit the production of cytokines, including IFN-γ, IL-4, IL-5, and IL-13.4,7,8

  • ICOS-L expression has been shown to be downregulated following interaction with ICOS.4

  • ICOS/ICOS-L interactions stimulate Tfh-cell differentiation in the lymphoid tissue, promote the survival of effector memory cells as well as B-cell selection, Ig class switching, and progression to plasma cells in germinal centers.4

  • Elevated expressions of ICOS and ICOSL have been found in patients with systemic lupus erythematosus.6,9

B7H: B7 homolog; B7RP: B7-related protein; CD: cluster of differentiation; DC: dendritic cell; ICOS: inducible T-cell costimulator; ICOSLG: inducible T-cell costimulator ligand; IFN-γ: interferon gamma; Ig: immunoglobulin; IL: interleukin; LICOS: ligand inducible T-cell costimulator; Tfh: T follicular helper.


  • 1.

    NCBI. Gene. ICOSLG inducible T cell costimulator ligand [Homo sapiens (human)].  www.ncbi.nlm.nih.gov/gene/23308. Accessed March 11, 2021.

  • 2.

    Yoshinaga SK, Zhang M, Pistillo J, et al. Int Immunol. 2000;12:1439-1447.

  • 3.

    Dong C, Temann UA, Flavell RA. J Immunol. 2001;166:3659-3662.

  • 4.

    Wikenheiser DJ, Stumhofer JS. Front Immunol. 2016;7:304.​

  • 5.

    Janke M, Witsch EJ, Mages HW, Hutloff A, Kroczek RA. Immunology. 2006;118:353-360.​

  • 6.

    Her M, Kim D, Oh M, Jeong H, Jeong H, Choi I. Lupus. 2009;18:501-517.​​

  • 7.

    Coyle AJ, Lehar S, Lloyd C, et al. Immunity. 2000;13:95-105.​​

  • 8.

    Vieira PL, Wassink L, Smith LM, et al. Eur J Immunol. 2004;34:1282-1290.​​

  • 9.

    Simpson N, Gatenby PA, Wilson A, et al. Arthritis Rheum. 2010;62:234-244.​​