The phylogeny of proteinase 3/myeloblastin, the autoantigen in Wegener's granulomatosis, and myeloperoxidase as shown by immunohistochemical studies on human leukemic cell lines.

Proteinase 3/myeloblastin (Pr3/MBN) is a serine protease found in primary granules of neutrophilic granulocytes and monocytes in man. This enzyme has been identified as the main autoantigen in Wegener's granulomatosis. Pr3/MBN was earlier identified in the promyelocytic cell line HL-60 and was assumed to be at least partly responsible for controlling proliferation and differentiation within the granulocytic-monocytic system. We have investigated 98 leukemic cell lines representing all lineages of the hemopoietic system. Pr3/MBN was found to appear in mature myeloblastic precursors and in CD34+ immature monoblastic cells and was restricted to the granulocytic and monocytic lineage. Myeloperoxidase (MPO) was found to be expressed earlier in development in the granulocytic lineage, but appeared later than Pr3/MBN in the monocytic lineage. The identification of cell lines which contained Pr3 only or MPO only may make them useful for demonstration of anti-neutrophil cytoplasmic antibodies in primary vasculitides.