IMMUNOPHENOTYPIC CHARACTERIZATION OF HUMAN PERITONEAL AND ALVEOLAR MACROPHAGES AND OF HUMAN BLOOD MONOCYTES DIFFERENTIATED IN THE PRESENCE OF EITHER GM-CSF OR M-CSF OR A COMBINATION OF GM-CSF M-CSF

In vivo, circulating blood monocytes (Mo) migrate into the various tissues where they undergo terminal maturation into macrophages (Mphi) with morphological and sometimes functional properties that are characteristic for the tissue in which they reside. This tissue-specific Mphi heterogeneity results from the immediate microenvironment, but may also originate from genetically distinct Mo subpopulations. The in vitro transformation of Mo to Mphi is thought to reflect the events of the in vivo maturation and thus is widely used as a model to analyse Mphi development. To study the heterogeneity within the mononuclear phagocyte system, we have investigated the phenotypic characterisation of mature tissue Mphi, blood Mo and Mo-derived Mphi cultured in medium with either GM-CSF, M-CSF or a combination of both cytokines. Tissue peritoneal and alveolar Mo showed different antigenic specificities, particularly concerning the transferrin receptor and CD68 and CD14 antigens. M-CSF-derived Mphi when compared to the other Mphi populations also exhibited a significantly increased expression of transferrin receptor and CD68 antigen. In contrast, GM-CSF treated cells which exhibited a better long term survival, showed notably more positivity for CD11b and CD32 antigens. These results show that the phenotypic heterogeneity of the different Mphi populations is limited and appears to result from discrepancies in the differentiation and/or activation of the cells. The location of the CD68 antigen, which is generally considered to be an intracellular protein, was investigated at the ultrastructural level and found to be exclusively situated at the outer cell membrane.