Stimulation of mesangial phagocytes does not influence the removal of established glomerular immune complex deposits

To test the hypothesis that mesangial phagocytes are involved in the removal of established glomerular immune complex deposits, either puromycin aminonucleoside (PAN) or polyvinyl alcohol (PVA) was given to rats as they recovered from chronic serum sickness glomerulonephritis. Both these substances increase the number and activity of mesangial macrophages. The nephritis was induced with radiolabelled cationized bovine serum albumin (BSA). After 10 days of such treatment, the animals were killed and the amount of isotope in whole renal cortex and in isolated glomeruli was measured. The volume fraction of subepithelial and mesangial electron-dense deposits was assessed by morphometric methods. Neither PAN nor PVA caused any significant alteration in any of these parameters. These results suggest that the methods by which well established glomerular immune complex deposits are removed do not involve mesangial macrophages to any major extent, and therefore differ from the systems which handle particulate matter and immune complexes as they arrive at the glomerular filter. The morphologic appearances of the deposits at the end of the experiment suggest extracellular dissolution in situ.