Clinical Significance of an Impaired Mononuclear Phagocyte System Immune Clearance in Human Nephritis

Dr D. Roccatello, Divisione Nefrologia e Dialisi, Nuova Astanteria Martini, P.za del Donatore di Sangue 3, I-10154 Torino (Italy) Dear Sir, Experimental models [1] suggest a critical role of the mononuclear phagocyte system (MPS) in the removal of immunologically active substances. The application of widely accepted techniques [2] to the study of the MPS function in immunologically mediated glomerulonephritis (GN) has provided a major step in understanding the pathogenesis of these diseases. However, conflicting results have been obtained even by using the same methodological approaches in similar samples of patients, making difficult to derive definitive conclusions for clinical purposes. To assess the prevalence and the clinical significance of a defective MPS function, we have reexamined our own four-year experience in detecting the splenic MPS immune clearance of IgG-sensitized 51Cr-labelled auto-logous red blod cells (RBC) [3] in patients with biopsy-proven GN. Patients included 17 cases of lupus nephritis, 10 of cryoglobulinaemia-associated GN, 6 of systemic vasculi-tis-associated GN, 9 Henoch-Schönlein, 1 of vascular amyloidosis, 28 of membranous GN, 10 of membrano-proliferative GN, 33 of primary IgA nephropathy, 10 of focal and segmental glomerulosclerosis, 5 of IgM mesan-gial GN, 1 of rapidly progressive postinfectious GN. Among the 43 patients with multisystem disorders with renal involvement, 29 cases with obvious urinary abnormalities ( > 1.5 g proteinuria/day and > 15 RBC/high-power microscopic field) associated with at least two systemic signs were found to have a prolongation of MPS immune clearance as compared to those with minimal urinary abnormalities ( < 0.7 g proteinuria/day and < 5 RBC/high-power microscopic field) without systemic manifestations (p < 0.05). In the lupus subgroup the MPS impairment was found to be related (p < 0.05) to the levels of IgG immune complexes detected by the Clq solid-phase test [4]. Moreover among the 87 patients with primary GN, 69 cases with obvious urinary abnormalities (as defined above) were found to have a significant decrease in MPS function as compared to those with minimal or no urinary signs (p < 0.02). This relationship was particulary strong (p < 0.01) in primary IgA nephropathy (32 cases), in which MPS dysfunction and IgA immune complex levels, detected by the conglutinin solid phase test [5], were