Evidence for a particular binding capacity of rat peritoneal macrophages to rat glomerular mesangial cells in vitro

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Abstract
The adhesion of normal rat peritoneal macrophages to normal rat glomerular epithelial or mesangial cells was studied in vitro after a 60-min incubation at 37.degree. C. After washing, the cell preparations were examined by phase contrast or scanning electron microscopy. Quantitative studies were also performed using macrophages labeled with 99mTc tin colloids. Peritoneal macrophages predominantly adhered to the cultured mesangial cells. The percentage of labeled macrophages adhering to these cells was .apprx. 10 times higher than that of labeled macrophages adhering to the cultured epithelial cells. This percentage increased proportionally to the number of labeled macrophages added and was strongly reduced by the prior incubation of macrophagic cells with aggregated IgG, with antifibronectin IgG or with F(ab'')2 fragments of antifibronectin IgG. The macrophage-mesangial cell interaction was significantly reduced by the prior incubation of mesangial cells with antifibronectin IgG or with F(ab'')2 fragments of antifibronectin IgG. Normal rat peritoneal macrophages preferentially adhere in vitro to normal rat glomerular mesangial cells, and this binding may be modulated, at least by the Fc receptor binding activity of macrophages or the fibronectin molecules available at the surface of macrophages and of mesangial cells.