Complement System and C4d expression in cases of Membranous nephropathy / Sistema complemento e expressão de C4d em casos de Glomerulopatia Membranosa

Abstract Introduction: Membranous nephropathy (MN) is one of the major causes of nephrotic syndrome. The complement system plays a key role in the pathophysiology of MN. Objectives: To identify the complement pathway possibly activated in MN cases and correlate the presence of C4d with more severe clinical and histological markers. Methods: Sixty nine cases from renal biopsy with membranous nephropathy were investigated. The presence of C1q was analyzed by direct immunofluorescence; and expression of C4d by immunohistochemistry. Clinical and epidemiological data were obtained upon biopsy request. Results: The presence of focal segmental glomerulosclerosis, global glomerulosclerosis, vascular lesions and tubulointerstitial fibrosis were collected by anatomopathological report. C4d(+) was found in 58 (84%), and C1q(+) was found in 12 (17%) of the cases. Twelve patients had C4d(+)/C1q(+), 46 had C4d(+)/C1q(-), and 11 patients had C4d(-)/C1q(-), probably indicating the activation of the classical, lectin and alternative pathways, respectively. Conclusion: C4d was associated with increased interstitial fibrosis, but not with clinical markers of poor prognosis. Through the deposition of C4d and C1q we demonstrated that all complement pathways may be involved in MN, highlighting the lectin pathway. The presence of C4d has been associated with severe tubulointerstitial lesions, but not with clinical markers, or can be taken as a universal marker of all cases of MN.

Resumo Introdução: A Glomerulopatia membranosa (GM) é uma das principais causas da síndrome nefrótica. O sistema do complemento desempenha um papel chave na fisiopatologia do GM. Objetivos: Identificar a via do complemento possivelmente ativada nos casos de GM e correlacionar a presença de C4d com marcadores clínicos e histológicos mais graves. Métodos: Foram investigados 69 casos de biópsia renal com GM. A presença de C1q foi analisada por imunofluorescência direta e a expressão de C4d por imunohistoquímica. Dados clínicos e epidemiológicos foram obtidos mediante solicitação de biópsia renal. Resultados: A presença de glomerulosclerose segmentar focal, glomeruloesclerose global, lesões vasculares e fibrose tubulointersticial foi coletada por relato anatomopatológico. C4d (+) foi encontrado em 58 (84%), e C1q (+) foi encontrado em 12 (17%) casos. Doze pacientes tinham C4d (+)/C1q (+), 46 tinham C4d (+)/C1q (-) e 11 pacientes tinham C4d (-)/C1q (-), indicando provavelmente a ativação da via clássica, da lectina e da alternativa, respectivamente. Conclusão: O C4d foi associado ao aumento da fibrose intersticial, mas não com marcador clínico de mau prognóstico. Através da deposição de C4d e C1q, demonstrou-se que todas as vias do complemento podem estar envolvidas em GM, destacando a via da lectina. A presença de C4d tem sido associada a lesões tubulointersticiais graves, mas não com marcadores clínicos, ou pode ser tomada como um marcador universal de todos os casos de GM.

Immunological studies in HBV-related chronic liver diseases.

Humoral immune response in chronic sequelae of HBV infection was assessed in the present study. Serum immunoglobulins (IgG, IgM, IgA) serum complement component C3 and C4 and circulating immune complex (CIC) were estimated in forty cases of HBsAg positive chronic active hepatitis and cirrhosis and sixty cases of age and sex matched healthy control subjects. Hypergammaglobulinemia was observed in chronic liver diseased state. All the three immunoglobulins, IgG, IgA and IgM were elevated significantly. The complement C3 and C4 were significantly decreased in patient group, while the levels of CIC were significantly increased. The increased immunoglobulin levels may be attributed to disorganised Kupffer cell system and also to B cell hyperactivity. The decreased complement levels may be attributed to decreased synthesis and/or increased consumption by increased CIC. A primary or an acquired defect in infected host to generate immune response might result in defective elimination of infected hepatocytes in chronic liver disease.