title: Granulocyte-macrophage colony-stimulating factor is a major macrophage fusion factor present in conditioned medium of concanavalin A-stimulated spleen cell cultures.
abstract: In 1983, we reported that the conditioned medium (CM) of spleen cell cultures treated with Con A greatly induced fusion of mouse alveolar macrophages within 2 to 3 days at a very high rate of more than 80% (Proc. Natl. Acad. Sci. USA 80:5583, 1983). In the course of examining macrophage fusion factors (MFF) present in Con A-CM, we found that IL-4 induced fusion of alveolar macrophages with a time course similar to that induced by Con A-CM. However, the maximal fusion rate induced by IL-4 (4 ng/ml) was about 35%. Furthermore, the fusion induced by Con A-CM was blocked only partially by adding IL-4 antibody, indicating that there are unknown MFF other than in Con A-CM. Of several other cytokines produced by Con A-stimulated spleen cells, IL-6 (20 ng/ml), IFN-gamma (45 ng/ml) and granulocyte-macrophage (GM)-CSF (10 ng/ml) greatly potentiated the fusion induced by 4 ng/ml of IL-4. The assay of these cytokines in Con A-CM proved that it contained 0.44 +/- 0.04 ng/ml of IL-4, 1.0 +/- 0.24 ng/ml of IL-6, 9.1 +/- 0.07 ng/ml of IFN-gamma, and 11.6 +/- 1.66 ng/ml of GM-CSF. When the potentiating effects of IL-6, IFN-gamma and GM-CSF on macrophage fusion were examined in the presence of 0.4 ng/ml of IL-4, only GM-CSF increased the fusion rate to the maximal level induced by Con A-CM at its physiologic concentration (10 ng/ml). The macrophage fusion induced by Con A-CM was greatly suppressed by adding antibody against GM-CSF. GM-CSF had a biphasic effect on growth and fusion, depending on its dose levels used: 0.01 to 0.1 ng/ml increased proliferation without inducing fusion and 10 ng/ml preferentially induced fusion. There was a negative relationship between macrophage growth and fusion. IL-4 was a potent inhibitor of proliferation of macrophages induced by GM-CSF. These results clearly indicate that GM-CSF is a major MFF present in Con A-CM.
authors.affiliation: Department of Biochemistry, School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Abe
authors.forename: Y
authors.initials: Y
authors.lastname: Ishimi
authors.forename: C H
authors.initials: CH
authors.lastname: Jin
authors.forename: M H
authors.initials: MH
authors.lastname: Hong
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: T
authors.initials: T
authors.lastname: Suda
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002459:Cell Fusion; D003208:Concanavalin A / Q000494:pharmacology; D003470:Culture Media; D004357:Drug Synergism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000008:administration & dosage / Q000502:physiology*; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis; D015847:Interleukin-4 / Q000008:administration & dosage / Q000096:biosynthesis; D008262:Macrophage Activation; D008264:Macrophages / Q000166:cytology*; D051379:Mice; D011650:Pulmonary Alveoli / Q000166:cytology; D013154:Spleen / Q000166:cytology
chemical_list: D003470:Culture Media; D003208:Concanavalin A; D015847:Interleukin-4; D007371:Interferon-gamma; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D002117:Calcitriol