Human recombinant granulocyte-macrophage colony-stimulating factor augments viability and cytotoxic activities of human monocyte-derived macrophages in long-term cultures.

In the present study we investigated the effect of human recombinant granulocyte-macrophage CSF (GM-CSF) on the in vitro maturation of human monocytes into macrophages, and followed the biochemical and functional changes in the cells during this process. Adherent human peripheral blood monocytes cultured for up to 3 weeks in the presence of GM-CSF were examined for viability and adherence, beta-glucosaminidase activity, oxidative burst activity, expression of fucosyl-mannosyl receptors, and TNF-alpha production. The cultured monocytes increased in size and protein content and matured into macrophages within 12 to 18 days. GM-CSF treatment increased by 2.5-fold the number of adherent cells after 2 weeks in culture, but did not change the beta-glucosaminidase and oxidative burst activities of the cells compared to nontreated controls. GM-CSF increased the capacity of monocyte-derived macrophages to bind yeasts and bacteria via fucosyl-mannosyl receptors, by both augmenting the viability of the adherent cell population and by elevating the expression of such receptors per cell. GM-CSF-treated macrophage cultures also showed elevated production of TNF-alpha. The results described here showed that GM-CSF facilitated the long-term maturation of monocytes into macrophages, augmented their capacity to capture bacterial and fungal cells, and elevated the release of cytokines involved in inflammatory and granulomatous reactions.