Expression of the M-CSF/CSF-1 Gene in Normal Human Alveolar Macrophages

Abstract

Among the factors which control the proliferation and differentiation of hematopoietic cells, macrophage colony stimulating factor (M-CSF) selectively stimulates the survival and growth of mononuclear phagocytes [1]. Whereas the exact in vivo function of M-CSF in humans has not yet been elucidated, it could be shown in vitro that human M-CSF induces blood monocytes (BM) to produce different cytokines, indicating a role in macrophage activation [2]. Furthermore, cultivated BM can be stimulated to produce M-CSF in an auto- stimulatory manner [3]. In this study we analyzed two subpopulations of normal human tissue macrophages for their M-CSF/CSF-1 gene expression as well as that of the corresponding growth factor receptor gene, probably encoded by the proto-oncogene c-fms [4]. We previously demonstrated that cultivated BM transform phenotypically as well as with regard to their isoenzyme pattern of a-naphthylacetate esterase in PM-like cells [5] and acquire during prolonged culture enzyme-cytochemical properties only found in AM such as positivity for tartrate-resistant acid phosphatase [6]. In addition to tissue macrophages, BM matured in vitro into PM- and AM-like cells were analyzed for their M-CSF/CSF-1 and c-fms gene expression in order to investigate whether autostimulation represents a regularly occurring phenomenon during normal human macrophage maturation.