Comparative analysis of the morphological, cytochemical, immunophenotypical, and functional characteristics of normal human peripheral blood lineage (-)/CD16(+)/HLA-DR+/CD14(-/lo) cells, CD14(+) monocytes, and CD16(-) dendritic cells

Human peripheral blood (PB) CD14(lo)/HLA-DR+ cells were initially described as a subset of mature monocytes. Recently, it has been suggested that thes e represent a part of a new subset of dendritic cells (DC), characterized b y the coexpression of MDC-8/HLA-DR/CD16. The aim of the present paper was t o analyze the morphological, cytochemical, phenotypical, and functional cha racteristics of PB CD16(+)/HLA-DR+ cells compared to both PB CD14(+) monocy tes and CD16(-) DC. In contrast to CD14(+) monocytes, purified CD16(+)/ HLA -DR+ cells displayed cytoplasmic veils and lacked cytoplasmic myeloperoxida se and a-naphthyl acetate esterase. Normal human PB CD16(+)/HLA-DR+ cells a lso displayed phenotypic characteristics different from those of CD14(+) mo nocytes: they lacked the CD64 Fc gamma receptor, showed lower levels of CD3 2, and expressed higher amounts of CD16 compared to CD14(+) monocytes. They also displayed a different pattern of expression of other antigens, includ ing CD14, HLA-DR, CD45RA, CD45RO, complement receptors and complement regul atory surface proteins, adhesion and costimulatory molecules, and cytokine receptors, among others. When compared to CD16(-) DC, CD16(+)/HLA-DR+ cells showed reactivity for CD16, dim positivity for CD14, higher expression of both Ig- and complement-receptors and lower reactivity for HLA-DR, adhesion , and costimulatory molecules (with the exception of CD86). The CD16(+)/HLA -DR+ cell subset displayed a higher Ig/complement-mediated phagocytic/oxida tive activity than CD16(-) DC, although this activity was significantly low er than that of mature monocytes. Regarding cytokine production at the sing le cell level, LPS plus IFN-gamma -stimulated PB CD16(+)/HLA-DR+ cells prod uced significant amounts of IL1 beta, IL6, IL12, TNF alpha, and IL8; howeve r, the percentage of cytokine-producing cells and the amount of cytokine/ce ll were lower in CD16(+)/HLA-DR+ cells than in CD14(+) monocytes. In additi on, upon comparing CD16(+)/HLA-DR+ cells with CD33(+++)/CD16(-) DC, we foun d that the percentage of cytokine-producing cells and the amount of cytokin e/cell were significantly different in both cell subsets. In summary, our r esults show that CD16(+)/HLA-DR+ cells clearly display different morphologi c, cytochemical, immunophenotypical, and functional characteristics compare d to both mature monocytes and CD16(-) DC. Interestingly, these cells are m ore frequent than other DC in normal human adult PB and cord blood samples, while they are less represented in normal bone marrow. (C) 2001 Academic P ress.