C3dg and MAC complement depositions in the renal histopathology of patients with lupus nephropathy

BACKGROUND: Childhood-onset systemic lupus erythematosus (SLE) refers to SLE with an onset before 18 years old. The key to the pathogenesis of SLE tissue inflammation and injury is complement activation. The presence of complement split C3dg and membrane attack complex (MAC) may indicate a worse prognosis for lupus nephritis (LN). This study investigated whether complement split C3dg and MAC depositions in the pathogenesis of LN are potential biomarkers of disease severity and tissue injury. METHODS: The data on patients with LN were retrospectively analyzed in our center between April 2018 and December 2020. The depositions of C3dg and MAC were detected by immunofluorescence staining. RESULTS: C3dg and MAC were both detected in specimens from 61.5% of patients. Patients with MAC depositions had a greater proportion of neurological disorders than those without MAC depositions (22.9% vs. 3.3%; P=0.044). We found significant differences in serum creatinine, urinary protein, and estimated glomerular filtration rate (eGFR) in all four groups of patients with differing degrees of C3dg and MAC depositions. CONCLUSIONS: This study suggests that C3dg and MAC depositions may be potential biomarkers for disease severity and tissue injury in LN. MAC and C3dg staining may be useful in routine studies of lupus biopsies to identify patients who need more aggressive treatment.