BIMODAL DISTRIBUTION OF PROTEINASE-3 (PR3) SURFACE EXPRESSION REFLECTS A CONSTITUTIVE HETEROGENEITY IN THE POLYMORPHONUCLEAR NEUTROPHIL POOL

Proteinase 3, which is known as an intracellular serine protease of ne utrophils, was detected at the surface of a subpopulation of freshly i solated PMN. The proportion of PR3-positive and -negative PMN, observe d by flow cytometry with anti-PR3 mAbs or ANCA autoantibodies, varies among individuals but is extremely stable for each individual over pro longed time periods, After PMN degranulation by FMLP with cyt, B, memb rane PR3 expression increases but the proportion of low and high PR3-e xpressing cells remains stable, The existence of a subset of PMN which spontaneously expresses PR3 and varies among individuals, may be rele vant to the pathogenesis of anti-PR3 ANCA autoantibody-related vasculi tis.