Functional analysis of monocyte-macrophages derived from nonadherent cord blood progenitor cells: correlation with the ontogeny of cell surface proteins

In this study we examine some of the phenotypic and functional characteristics that accompany the differentiation of monocyte-macrophages from nonadherent precursors present in cord blood. Class II major histocompatibility complex (MHC) molecules identified by monoclonal antibody (mAb) L243 were the earliest monocyte-macrophage-associated antigens to be expressed. CD14 molecules, identified by mAb MO.2, and the transferrin receptor, identified by mAb OKT9, increased linearly over the 21-day culture period. In contrast, Fc gamma R were not expressed on these cells until 14 days of culture. Fc gamma RI was present on approximately 80% of the cells, whereas Fc gamma RII and Fc gamma RIII were present on 30% and 20% of the cells, respectively. Functional activity of the nonadherent cell-derived monocyte-macrophages paralleled the phenotypic maturation of these cells. The capacity to stimulate a mixed leukocyte reaction paralleled the expression of class II MHC molecules. Similarly, the capacity to phagocytose Escherichia coli and Staphylococcus aureus paralleled the appearance of CR3. Indeed, phagocytosis of these organisms was partially blocked by mAb OKM-1. These studies demonstrate that monocyte-macrophages derived from cord blood nonadherent mononuclear cells are a useful population with which to characterize human macrophage differentiation and functional and phenotypic heterogeneity.