Generation and characterization of monoclonal antibodies to human type-5 tartrate-resistant acid phosphatase: Development of a specific immunoassay of the isoenzyme in serum

We have characterized four monoclonal antibodies (mAbs) to the purple ('tartrate-resistant,' band 5) acid phosphatase of the human osteoclast (TRAP) and used these to develop a specific serum immunoassay. All four mAbs are of high affinity (K(a) = 1-5 x 10⁸ L/mol) with a very fast K(assoc) (0.2-2.0 x 10⁵ L mol^-1 s^-1) and a moderate K(dissoc) (1-3 x 10^-3 s). Two of the mAbs were selected to develop a time-resolved fluorescence immunoassay to measure serum concentrations of TRAP. The mean serum immunoreactive TRAP in a group of healthy premenopausal women and men was 3.7 ± 1.8 μg/L (mean ± SD) and 3.5 ± 1.6 μg/L, respectively. Significantly higher concentrations of TRAP were found in postmenopausal women (6.3 ± 2.3 μg/L) and in eight patients with Gaucher disease (19.3 ± 4.7 μg/L). Further studies are required to investigate the value of serum TRAP as a marker of bone resorption.