Human Inducible T-Cell Costimulator (ICOS) Protein

Background

Inducible T-cell costimulator (ICOS), a member of the CD28 family of costimulatory receptors, is expressed on activated T cells and plays a crucial role in modulating immune responses. ICOS, encoded by the ICOS gene, provides an essential costimulatory signal that promotes T cell activation, differentiation, and cytokine production. Upon activation by its ligand, ICOS ligand (ICOSLG or CD275), which is found on antigen-presenting cells (APCs) like B cells, dendritic cells, and macrophages, ICOS triggers intracellular signaling pathways that enhance T-cell effector functions. ICOS is crucial for both humoral and cell-mediated immunity. It enhances T-helper cell responses, particularly in the germinal centers of lymphoid tissues, where it influences B cell differentiation and supports antibody production. ICOS signaling also helps maintain the balance between effector and regulatory T cells, impacting inflammation control and immune tolerance. The ICOS/ICOSLG pathway is vital in the immune system's ability to fight infection and respond to vaccination, as well as in controlling immune tolerance to prevent autoimmune diseases.