The TX42.1 monoclonal antibody specifically recognizes CD226 which is also known as DNAX accessory molecule-1 (DNAM-1), Platelet and T-cell activation antigen 1 (Pta1), or T lineage-specific activation antigen 1 (TLiSA1). CD226 is an ~65 kDa type I transmembrane glycoprotein that is encoded by Cd226 (CD226 antigen) which belongs to the immunoglobulin superfamily (IgSF). The N-terminal extracellular region of CD226 (DNAM-1) contains two C2 type Ig-like domains which are followed by a transmembrane region and a cytoplasmic tail with predicted phosphorylation sites involved in signaling. This adhesion molecule is expressed on subsets of CD4+ and CD8+ T cells and B cells, NK cells, monocytes, macrophages, and platelets. CD226 (DNAM-1) associates with leukocyte function associated antigen-1 (LFA-1) and is involved in TCR-mediated signal transduction for T cell proliferation and differentiation. Interactions between the CD226 (DNAM-1) activating receptor and its ligands, CD112 and CD155, results in cellular signaling that promotes innate and adaptive immune responses, including the activation, differentiation and survival of cytotoxic cells.