Human Inducible T-Cell Co Stimulator Ligand (ICOSLG) Protein

Background

Inducible T-cell costimulator ligand (ICOSLG), also known as B7-H2 or CD275, is a critical immunoregulatory protein in the B7 family that provides costimulatory signals to T cells. ICOSLG serves as a ligand for ICOS (Inducible T-cell Costimulator), a receptor expressed on activated T cells. Through its interaction with ICOS, ICOSLG plays an essential role in modulating adaptive immune responses, particularly influencing T-cell differentiation, proliferation, and the formation of memory T cells. This interaction is crucial for both protective immunity and immune tolerance, enabling the immune system to respond robustly to pathogens while preventing autoimmunity. ICOSLG is primarily expressed on antigen-presenting cells (APCs), such as B cells, dendritic cells (DCs), macrophages, and certain epithelial cells in mucosal tissues. Its expression is inducible and can be upregulated during inflammation or immune activation by signals from pro-inflammatory cytokines like interferon-gamma (IFN-γ). The ICOS/ICOSLG axis is especially important for the regulation of germinal center formation in lymphoid tissues, where it facilitates B cell differentiation and antibody production. ICOSLG is also implicated in the maintenance of regulatory T cells (Tregs) and T-helper 17 (Th17) cells, thereby contributing to immune homeostasis and controlling inflammation.