Immunostimulators induce granulocyte/macrophage colony-stimulating activity and block proliferation in a monocyte tumor cell line.

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Abstract
Monocyte tumor [mouse] cell line PU5-1.8 does not normally produce colony-stimulating activity (CSA) required by granulocyte and macrophage progenitors to proliferate and mature in agar. CSA is induced in the culture line by as little as 10 ng/ml [Salmonella typhosa] endotoxic lipopolysaccharide (LPS), with maximum CSA production and release to the medium between 2 and 3 days of incubation. Derived lipid A, but not alkali-treated LPS, is also active. Induction requires RNA and protein synthesis, but is not blocked by mitomycin C or Colcemid. Other inducers of CSA include Mycobacterium BCG, tuberculin protein preparation purified protein derivative, zymosan and phorbol myristate. All inducing agents are specific inhibitors of the monocyte tumor cell proliferation in vitro. Latex beads, another macrophage-activating agent, are rapidly phagocytosed by PU5-1.8 cells, but neither inhibit growth nor induce CSA.

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