We studied the effect of low-fluence photodynamic treatment with Photosence preparation on functional properties of macrophages and endothelium in vitro. It was shown that low-intensity photodynamic treatment did not affect viability of these cells. Exposure (0.25 J/cm(2)) of endothelial cells loaded with Photosence did not change the expression of adhesion molecules, but reduced adhesion of peripheral blood mononuclears to these cells. The same low-intensity exposure inhibited phagocytic activity of macrophages and reduced activity of matrix metalloproteinase-9 produced by them.