The SKII.4 monoclonal antibody specifically binds to the Poliovirus Receptor (PVR) which is also known as CD155, or Nectin-like protein 5 (NECL5). PVR is a ~70 kDa nectin-like type I transmembrane glycoprotein that belongs to the PVR-related (PRR) family within the Ig superfamily. In addition to two cell surface PVR isoforms (alpha and delta), two secreted PVR isoforms (beta and gamma) have been reported that share the same three Ig domains but differ in their C-termini. PVR is expressed on monocytes, macrophages, endothelial cells, epithelia cells, CD34+ thymocytes, and neurons. In addition to serving as a receptor for poliovirus and cytomegalovirus, PVR functions as an adhesion molecule involved in cell-cell and cell-matrix adhesion through interaction with CD96 (TACTILE), Nectin 1-3 (CD111, CD112, CD113), CD226, and vitronectin. PVR promotes natural killer (NK) cell adhesion to and lysis of target cells.