Biochemical characterization of human myeloperoxidase using three specific monoclonal antibodies

We have developed three monoclonal antibodies (moAbs), MA1, MA3 and MB1, which react with different antigenic determinants of human myeloperoxidase (MPO). In MPO-positive culture cell lines, HL-60 and NKM1, analysis of MPO by pulse-chase experiments followed by immunoprecipitation with these moAbs revealed that MPO was composed of subunits of 59K, 18K and 14.8K dalton polypeptides which are plausibly derived from the 89 K precursor. MA1 and MB1 react with both the precursor and the mature forms of MPO. MA3 reacts with only the mature forms of MPO. Blocking experiments on MPO-related functions revealed that the three moAbs could be divided into two groups. MA1 and MA3 inhibit MPO activities such as tetraguaiacol formation, iodide oxidation and luminol-dependent chemiluminescence, while MB1 shows no such inhibition.