Role of marrow-derived monocytes and mesangial cells in removal of immune complexes from renal glomeruli.

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Abstract
Phagocytosis of i.v. administered immune complexes by cells in the mesangium was investigated. The model used was that of exchange marrow transplantation between Chediak-Higashi (CH) mice and syngeneic partners after X-irradiation. This model was chosen since marrow-derived marcrophages could be differentiated from resident mesangial cells by the presence of the characteristic giant lysosomes in phagocytic cells of the CH mice. Injected immune complexes were cleared normally and localized in the glomerular mesangium in CH or C57BL/6J mice receiving C57BL/6J or CH marrow. C57BL/6J mice with CH marrow injected with immune complexes prepared with reduced and alkylated antibodies accumulated many cells within the mesangium that contained giant lysosomes and electron dense deposits. Deposits were not found in cells with subplasmalemmal microfilaments and peripheral dense bodies. The cells in the mesangium of CH mice with C57BL/6J marrow that contained electron dense deposits were devoid of giant lysosomes. Marrow-derived monocytes contribute to mesangial hypercellularity after deposition of immune complexes. Phagocytosis of immune complexes localized in the glomerular mesangium was by marrow-derived monocytes rather than by mesangial cells.