Studies on the control of macrophage division during the inflammatory process.

It has been suggested that the regulation of macrophage division may be afforded by the release of soluble mitogenic factors into inflammatory exudate. We have examined for macrophage mitogenic activity in exudates and sera obtained from animals with chronic inflammatory lesions and compared them with fluids from an acute lesions. Both acute and chronic exudates were able to promote DNA synthesis, however acute exudate had higher activity. Although we were able to detect mitogenic activity in the sera obtained from animals with acute pleurisy, we were unable to detect any activity greater than control in sera obtained from animals with chronic inflammatory lesions. We propose the presence of mitogenic factors for macrophages in both animals with acute and chronic lesions may help to explain the increasing predominance of mononuclear cells seen during the progression of acute to chronic inflammation.