ICOS / AILIM / CD278 is related to the CD28 superfamily and is highly expressed on activated T cells as well as regulatory T cells and is crucial for the survival and function of T cells, Th2 cell differentiation and for lung inflammatory responses. ICOS/ICOS ligand immune checkpoint pathway with binding ICOS / AILIM / CD278 to ICOS Ligand / B7-H2 activates a cascade of intracellular signaling molecules that prevent apoptosis and lead to the production of cytokines such as IL-4 and IL-13. To date, ICOS Ligand / B7-H2 has been reported to be expressedby B cells, non-lymphoid cells, and lung epithelial cells but not by T cells or innate lymphoid cells and is downregulated upon binding to ICOS as an immunoregulatory mechanism.
Maazi H et al. ICOS:ICOS-Ligand Interaction Is Required for Type 2 Innate Lymphoid Cell Function, Homeostasis, and Induction of Airway Hyperreactivity. Immunity. 2015 Mar 17;42(3):538-51