Granulocyte-macrophage colony-stimulating activity in the serum of mice stimulated with homogenates of Trypanosoma gambiense.

Infection of mice with Trypanosoma gambiense induced a rapid and transient increase in levels of serum granulocyte-macrophage colony-stimulating activity (GM-CSA) followed by an increase in the numbers of circulating neutrophils and large mononuclear cells. Similar phenomena were observed in mice injected with a trypanosomal homogenate. In such mice, levels of GM-CSA were markedly elevated as early as 1-2 days after administration of the homogenate and then rapidly decreased. Numbers of circulating neutrophils and large mononuclear cells increased within 2 and 3 days after injection of the homogenate, respectively. Induction of GM-CSA by the trypanosomal homogenate promoted colony formation by normal spleen cells, but did not support colony formation by spleen cells from mice treated with 5-fluorouracil. Serum levels of GM-CSA were elevated by injection of crude trypanosomal membrane fractions, but not by soluble components found in supernatants from centrifuged trypanosomal homogenates. GM-CSA-inducing ability of the crude membrane fraction was sensitive to heating at 60 degrees C for 30 min, treatment at pH 2.0, pronase digestion, periodate oxidation, and exposure to 0.1% sodium dodecyl sulphate. This biological activity was also reduced by trypsinization of living trypanosomes before preparation of membrane fractions. These findings suggest that the active component of parasites to induce GM-CSA is associated with a glycoprotein in the surface coat of T. gambiense. GM-CSA may be related to the haematological and immunopathological alterations that occur in African trypanosomiasis.