The51D6 monclonal antibody recognizes human CD167a also known as discoidin domain receptor, DDR1, neuroepithelial tyrosine kinase, epithelial-specific receptor kinase, tyrosine kinase receptor E (trkE), cell adhesion kinase (CAK), PTK3, and RTK6. CD167a is a membrane type II receptor kinase, containing a factor VIII-like domain. Three isoforms of CD167a have been reported. Predicted molecular weights are: isoform 1, approximately 101.5 kD, isoform 2, approximately 101 kD, and isoform 3 approximately 97 kD. CD167a is expressed on epithelial cells, keratinocytes, leukocytes, monocytes and has been reported to be overexpressed in some breast carcinomas. CD167a expression can be upregulated by p53. CD167a has been reported to interact with a variety of proteins including collagen type II alpha 1, collagen type III alpha 1, collagen type V alpha 2, collagen type XI alpha 1, phospholipase gamma 1, SHC, and the lipid-anchored docking protein FRS2. CD167a can be phosphorylated on Y513. Animal studies suggest that CD167a is involved in arterial wound healing. The51D6 antibody has been shown to be useful for flow cytometric detection of human CD167a as well as immunoprecipitation.