– CD112 is a type I transmembrane glycoprotein belonging to the Immunoglobulin superfamily. It comprises one Ig-like V-type domain and two Ig-like C2-type domains in the extracellular region. The V domain is believed to mediate nectin binding to its ligands. Nectin2 is known to bind the pseudorabies virus, and herpes simplex virus2 (HSV2), involving in cell to cell spreading of these viruses. It does not bind poliovirus. As a homophilic adhesion molecule, CD112 is found concentrated in adherens junctions, and exists on neurons, endothelial cells,epithelial cells and fibroblasts. CD112 has been identified as the ligand for DNAM-1 (CD226), and the interaction of CD226/CD112 mediates cytotoxicity and cytokine secretion by T and NK cells. The costimulatory responses may be a critical component in allergic reactions and may therefore become targets for anti-allergic therapy.