Mouse CD226 (DNAM-1) is a 65 kd glycoprotein of a member of Ig super-family adhesion molecule containing 2 immunoglobulin-like domains. It is associated with leukocyte function associated antigen-1 (LFA-1) involving in TCR-mediated signal transduction for T cell proliferation and differentiation. CD226 is also involved in NK cell and T cell mediated cytotoxicity against certain tumors. CD226 (DNAM-1) is constitutively expressed on naïve CD8+ and CD4+ T cells, macrophages, and NK cells. It was reported that CD226 expression is up-regulated on Th1 cells, but down-regulated on Th2 and Th0 cells. CD155 and CD112 are the ligands for CD226.