Background/Aim Autoantibodies against C1q (anti-C1q) have been found in a number of autoimmune and renal diseases. They are fully investigated in adult patients with systemic lupus erythematosus (SLE), and a positive correlation between the level of anti-C1q and severity of lupus nephritis (LN) has been detected. The importance of anti-C1q in children with SLE has not yet been fully investigated. Furthermore, the clinical importance of anti-C1q in other forms of glomerulonephritis remains to be elucidated. The aim of this study was to investigate anti-C1q in children with acute poststreptococcal glomerulonephritis (APSGN) and LN. To investigate and to find the relationship between its presence and the severity and the prognosis of the disease. Methods: This section study was carried out on 44 cases and 20 control aged from 4 to 18 years. The cases were admitted to the Nephrology Department in Mansoura University Child Hospital. Investigations were performed in Microbiology and Immunology Department of Benha Faculty of Medicine. Children under study were classified into three groups: Group I: included 28 cases (19 males and 9 females) suffering from APSGN. Group II: included 16 cases (5 males and 11 females) suffering from LN. Group III: (Control) included 20 age and sex matched controls. Patients and controls were subjected to: Indirect immunofluorescence assay (IFA) was used for detection of circulating antinuclear antibodies (ANA). Serum level of anti-C1q antibodies was detected by enzyme-linked immunosorbant assay (ELISA), while complement C3 and C4 levels were measured by radial immunodiffusion method. Results: 22 (50%) cases were positive for anti-C1q compared to 0 of 20 healthy controls. Anti-C1q was detected in 15 patients (53.6 %) with APSGN and 7 cases (43.7%) with LN and was associated with activity in LN and with disease severity in patients with APSGN. C3 level was decreased in all APSGN cases, as compared to 11 cases (68.7 %) with LN. Regarding C4, 8 cases (28.5%) with APSGN showed decreased level as compared to 8 cases (50%) with LN.
In conclusion: Anti-C1q is associated with active LN in children and can be a useful marker for detection of renal affection and the prognosis of the disease.
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