Erythrocyte and glomerular C4d deposits as a biomarker for active lupus nephritis

Introduction: Lupus nephritis (LN) is a serious manifestation of systemic lupus erythematosus (SLE) and histologically evident even in those without clinical manifestations of renal disease. Aim of the work: To assess C4d on erythrocytes (E-C4d) and glomerular deposits (G-C4d) in SLE patients and study its association to LN and disease activity. Patients and methods: 61 subjects were enrolled including 15 with LN (study group); 15 with renal disease not due to SLE (control A group); 16 SLE patients with no renal affection (control B group) and 15 healthy individuals (control C group). Flow cytometry system was used for C4d immunohistochemical staining. SLE disease activity index (SLEDAI) was assessed for SLE patients. Results: The age was comparable among groups; for LN patients was 28.3 +/- 8.2 years; group A (35.9 +/- 13.3); group B (27.1 +/- 8.8) and group C (29.4 +/- 7.1) (p = .06). Patients were mostly females. The disease duration of LN patients was 1-2 years; group A (3-5 years) and group B (5-10 years). E-C4d and G-C4d deposits were significantly higher in LN patients (8.08 +/- 2.93 and 2.3 +/- 0.97) in comparison to the control groups (A/B/C) (A: 3.78 +/- 0.38 and 0.6 +/- 1.12; B: 3.72 +/- 0.32; C: 3.55 +/- 0.44 p <.001, p < .001, p < .001 MFI respectively). E-C4d and G-C4d significantly correlated with LN activity (r = 0.8, p < .001 and r = 0.7, p = .005) and with SLEDAI (r = 0.9, p = .005 and r = 0.8, p = .002, respectively). Conclusion: Erythrocytic C4d correlated significantly with the LN activity which might serve as a potential biomarker for renal activity in the future instead of biopsy and may further help in the optimum follow up of LN patients. (C) 2017 Egyptian Society of Rheumatic Diseases. Publishing services provided by Elsevier B.V.