Cell surface heterogeneity of human blood neutrophils and monocytes

Until recently, human blood neutrophils (PMN) and monocytes have been considered to be homogeneous cell populations. However, much evidence has accumulated on their functional heterogeneity. This functional heterogeneity suggests the existence of different subsets of myeloid cells analogous to T and B subsets of lymphoid cells. The goal of this study was to investigate this question of myeloid subsets by examining myeloid cells for cell surface reactivity for IgG and complement (C). Normal PMN and monocytes were examined from 60 subjects for the presence of two types of IgG-Fc receptors and two activated C components, C3b and C3d. Most PMN and monocytes showed Fc receptor activity for rabbit IgG (Fc-R). In addition, the majority of monocytes but very few PMN reacted with human IgG (anti-Rh0) coated Rh-positive erythrocytes (Fc-H). Most PMN and monocytes showed C receptor reactivity for C3b, but only a minor subpopulation of both myeloid cells had C3d receptors. These data provide evidence that human blood myeloid cells may be composed of subsets with different membrane marker reactivities.