Icos
Function
Stimulatory receptor expressed in activated or antigen-experienced T-cells that plays an important role in the immune response (PubMed:11343123). Upon binding to its ligand ICOSL expressed on antigen presenting cells (APCs), delivers costimulatory signals that enhances all basic T-cell responses to a foreign antigen, namely proliferation, secretion of lymphokines including IL10, up-regulation of molecules that mediate cell-cell interaction, and effective help for antibody secretion by B-cells (PubMed:10657606). Acts also as a costimulatory receptor critical for the differentiation of T follicular regulatory cells upon immune challenges such as viral infection (PubMed:36754569). Mechanistically, potentiates TCR-induced calcium flux by augmenting PLCG1 activation and actin remodeling (PubMed:27693916). In addition, activates PI3K signaling pathways independently of calcium flux (PubMed:19915142, PubMed:27693916). Essential both for efficient interaction between T and B-cells and for normal antibody responses to T-cell dependent antigens. Prevents the apoptosis of pre-activated T-cells. Plays a critical role in CD40-mediated class switching of immunoglobin isotypes (PubMed:11343122).
Post-translational modifications
N-glycosylated.
Tissue Specificity
Expressed on activated T-cells and resting memory T-cells. High expression seen in the thymic medulla and in the germinal centers and T-cell zones of lymph nodes and Peyer patches. Expressed at low levels in the spleen.
Cellular localization
- Cell membrane
- Single-pass type I membrane protein
Alternative names
CD278, Ailim, Icos, Inducible T-cell costimulator, Activation-inducible lymphocyte immunomediatory molecule, CD28 and CTLA-4-like protein, CD28-related protein 1, CCLP, CRP-1