Human non-transformed monocyte-derived macrophage cell lines

Expression of membrane C1q in human monocyte-derived macrophages is developmentally regulated and enhanced by interferon-gamma

The present study investigated when during "in vitro" maturation macrophages (MPhi) express membrane C1q (mC1q), and whether cell activation affects expression and function of mC1q. Although C1q mRNA was repeatedly detected in freshly isolated monocytes using reverse transcriptase-polymerase chain reaction, C1q protein was observed only in developing MPhi from day 1 to 4 on using immunodetection and flow cytometry. However, the quantity of mC1q and other MPhi membrane proteins differed strikingly in cells from different donors. We report here for the first time that CD14(+) and CD14(-) mC1q-bearing MPhi can develop, and that interferon-gamma increases mC1q display at the cell surface, and mC1q-mediated phagocytosis.

Autologous human macrophages and anti-tumour cell therapy

Most technical problems concerning the production of human macrophages have been resolved by cultures in hydrophobic plastic, gas-permeable bags. This process enables collection of non-adherent macrophages and is well adapted to the safety requirements of cell therapy. Under optimized culture conditions, about one billion macrophages are currently obtained from a single leukapheresis product. In most clinical trials, macrophages have been activated by interferon-gamma (IFNgamma). The injections have little or no toxic effect. The anti-tumour activity of the intravenous (i.v.) administrations is more pronounced in certain protocols than in others. The mechanism remains poorly understood. In vitro, the cytolytic effect of macrophages requires cell-to-cell contact but macrophages injected i.v. show no particular tropism for tumour tissue. This could result from modifications in adhesion molecules occurring during monocyte-macrophage differentiation which might modify recruitment in inflammatory foci. Macrophages can, however, infiltrate tumour cell clusters, which could explain their improved efficacy when injected intratumorally (i.t.). Moreover, several arguments would favour the use of macrophages as human tumour antigen-presenting cells (APCs). In vitro, macrophages are as efficient as monocyte-derived dendritic cells (MDDCs) in stimulating cytotoxic T lymphocyte (CTL) clones or circulating CTL precursors.

Establishment of mononuclear phagocyte cell lines

Macrophage cell lines have been derived from cells residing in a number of tissues from a variety of species. In this report, the methods used to obtain these cell lines are reviewed and a simple and efficient method for generating nonvirus-transformed lines from individual cloned progenitors located in mouse tissues is described.

Monocyte proliferation in a cytokine-free, serum-free system

The aim of this study was to establish a cytokine-free, serum-free system which would enable the long-term survival and proliferation of human peripheral blood monocytes. Monocytes were isolated from peripheral blood mononuclear cells (PBMC) by adherence to untreated plastic petri dishes and maintained up to 6 weeks in serum-free medium (SFM) consisting of IMEM, insulin, transferrin, sodium selenite and BSA. Maximal cell proliferation occurred during the first 2 weeks of culture and corresponded to the appearance of large numbers of pure, nonadherent culture-derived macrophages. Monocyte maturation was characterised by the modulation of specific cell surface antigens. The percentage of cells staining for the transferrin receptor increased with time, whereas the percentages of cells expressing CD11b, CD11c and HLA-DR remained greater than 60% for the 15 days studied. The mean fluorescent intensities (MFI) of all these antibodies increased significantly with time. The only differences found between the adherent and nonadherent cells, using the above antibodies, were with the MFI for CD11b and CD11c. In both cases, the intensity of staining was significantly greater in the adherent cells. Estimation of cytokine production by cells maintained for 5 weeks in SFM found that they constitutively produced large amounts of macrophage colony-stimulating factor (M-CSF) in the absence of any exogenous stimuli. These cells were also found to secrete high levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) during the 1st week and granulocyte macrophage colony-stimulating factor (GM-CSF) during the 3rd week. However, the addition of exogenous GM-CSF (5 U/ml, S5) was found to significantly inhibit monocyte proliferation up to 17 days. This is the first report of proliferation associated with long-term survival of culture derived macrophages in a serum-free, cytokine-free system.

Human cytomegalovirus productively infects primary differentiated macrophages

Monocytes are one of the predominant cell types in the peripheral blood that are infected by human cytomegalovirus (HCMV). Although virus can be detected in these cells in vivo, HCMV replication in cultured monocytes has been unsuccessful. In this study, we demonstrate efficient HCMV replication in cultured monocytes. HCMV permissiveness in these cells was dependent on nonadherent cell-induced stimulation of the monocyte, with subsequent morphological differentiation into macrophages. Approximately 40% of the cells infected by virus were detected by immunofluorescent staining with both immediate-early and late antibodies. In addition, viral plaque assays demonstrated significant productive infection of macrophages. These observations are consistent with the suggestion that the monocyte/macrophage serves as a source of viral amplification and dissemination.