Anti-ROBO4 antibodies are used in the immunodetection of the protein roundabout guidance receptor 4. In humans, the canonical protein has a reported length of 1007 amino acid residues and a mass of 107.5 kDa. Alternative splicing is reported to yield 3 different isoforms for this protein. It is notably expressed in endothelial cells. A member of a the ROBO protein family, ROBO4 is a known receptor for Slit proteins, at least for SLIT2, and seems to be involved in angiogenesis and vascular patterning. Post-translational modifications have been described, including glycosylation. Synonyms for this target antigen include ECSM4, MRB, roundabout homolog 4, roundabout homolog 4, magic roundabout, roundabout, axon guidance receptor, homolog 4, and AOVD3.