Detection of Bone‐type Alkaline Phosphatase by Monoclonal Antibodies Reacting with Human Osteosarcoma‐associated Antigen

The antigen detected by monoclonal antibodies reacting with human osteosarcoma‐associated antigen was shown to he a phosphatidyl‐inositol (Pl)‐glycan‐anchored protein, which can be released from the cell surface by PI‐specific phospholipase C‐treatment. The antigen detected by 2D3 and 2H10 antibodies exhibited alkaline phosphatase activity. Both antibodies strongly reacted with bone‐type alkaline phosphatase. However, importantly, immunohistochemical analysis demonstrated that 2D3 and 2H10 did not react with alkaline phosphatase present in kidney or liver. In addition, neither placental nor intestinal alkaline phosphatase was recognized by 2D3 and 2H10 antibodies. These results indicated that two monoclonal antibodies, 2D3 and 2H10, are highly specific for bone‐type alkaline phosphatase and can distinguish bone alkaline phosphatase from liver alkaline phosphatase in spite of the fact that liver and bone alkaline phosphatase are encoded by the same gene.