Inducible T cell co-stimulator receptor (ICOS)

The Inducible T cell co-stimulator receptor (ICOS, also known as CD278) is a cell surface co-stimulatory molecule belonging to the immunoglobulin superfamily, highly homologous to CD28. It is not expressed on resting T cells but is rapidly upregulated following T cell receptor (TCR) engagement and/or CD28 co-stimulation. ICOS provides a crucial secondary signal that promotes the activation, differentiation, and survival of both CD4+ and CD8+ T cells, and is particularly essential for the formation and function of T follicular helper cells, supporting B cell affinity maturation within germinal centers. Its main ligand, ICOSL (ICOS ligand), is predominantly expressed on antigen-presenting cells. The ICOS-PI3K signaling pathway is central to its effects on T cell cytokine gene induction, proliferation, and mediating class-switch recombination in B cells. Pharmacological modulation of ICOS signaling is explored for cancer immunotherapy, autoimmunity, and chronic inflammation due to its pivotal role in adaptive immune responses[1][2][4][6].

Other names

Inducible costimulatorInducible co-stimulatory moleculeCD278

Modulation of T cell activation by providing a secondary co-stimulatory signal in concert with the T cell receptor (TCR)[2][1] Activation of phosphoinositide 3-kinase (PI3K) pathway, leading to downstream Akt activation and cytokine gene expression; particularly important for the generation of follicular B helper T cells and germinal center reaction[4] Promotes proliferation, survival, and cytokine production in activated T cells[1][2][4]