Enhancement of the Frequency of Tumor-associated Macrophages Capable of in Vitro Proliferation by Colony-stimulating Factors and Heterologous Erythroc

Abstract

Limiting dilution analysis was used to analyze the effects of colony-stimulating factors on the in vitro proliferation of tumor-associated mac~ophages and resident peritoneal macrophages. Specifically, _macrophage colonystimulating factor and granulocyte/macrophage colony- ' ' stimulating factor were examined as both crude natural and recombinant forms for enhancement of proliferative responses of these two populations. Sheep erythrocytes were also assayed for their ability to stimulate proliferation. Analysis of data showed little significant difference between proliferation of resident peritoneal macrophages and tumor~ associated macrophages with the factors that were assayed. Further analysis of supernate isolated from cultured tumor cells indicated the production of colony-stimulating factors by the tumors. This suggests that some tumors may stimulate macrophage proliferation.