The monoclonal antibody clone 555 recognizes CD171, a single pass type I membrane glycoprotein belonging to the immunoglobulin superfamily. Also known as L1CAM (L1 cell adhesion molecule) or NCAM-L1, CD171 belongs to a subgroup of cell adhesion molecules, which consists of six Ig-like domains, five fibronectin type III (FNIII)-like domains, a transmembrane region and a cytoplasmic domain. Expression of CD171 is found on tetanus-toxin positive neurons1, endothelial cells, certain epithelial cells, reticular fibroblasts and several malignant tumors including colon and breast carcinomas, colon melanoma, tumor cells of neuronal and mesothelial origin, where a role of CD171 in augmenting tumor growth has been demonstrated. Thus, CD171 is considered a novel marker for carcinoma progression.
CD171 displays binding to a number of ligands including homophilic interaction with itself and heterophilic binding to integrins, other cell adhesion molecules, extracellular matrix molecules and thus plays a vital role in cell adhesion and signal transduction. It is involved in the development of the nervous system and regulates processes such as neuron–neuron adhesion, myelination, axonal guidance, and neuronal migration.
