#1707 Antiphospholipid antibodies in lupus nephritis
Authors: Monova Daniela , Todorov Todor , Monov Simeon 
Published: May 2024

Abstract

Background and Aims
Antiphospholipid antibodies (aPL) constitute a heterogeneous family of antibodies against anionic phospholipids or phospholipid-binding proteins. They may occur in association with autoimmune diseases, infections, and sometimes in the general population. Lupus nephritis (LN) is a major manifestation of systemic lupus erythematosus (SLE).
The aim of this study was to investigate the association of aPL with clinical activity, renal damage, renal activity and outcomes in patients with LN.

Method
A total of 157 patients (11 male, 146 female, age between 17 and 58 years) with LN were included in this study. The International Society of Nephrology/Renal Pathology Society (ISN/RPS) 2003 classification of LN was used to classify the patients into LN subsets. Histopathological renal activity and damage were estimated using the Activity Index (AI) and Chronicity Index (CI), respectively. Levels of anticardiolipin (aCL) antibodies, anti-β2-glycoprotein I (anti-β2-GPI) antibodies and lupus anticoagulant (LAC) were measured, and other clinical and pathological data were also obtained. Long-term renal outcome was determined by the estimated glomerular filtration rate (eGFR) and the Chronic Kidney Disease stage, after a median follow-up of 20,5 ± 8, 7 years, counting from the occasion of the first renal biopsy. Renal and extra-renal symptoms were analyzed. Patients which have more than one class LN features, were excluded from the study. The treatment includes standard treatment for LN, inhibitors of the angiotensin system in patients with hypertension and proteinuria, steroids, anticoagulants, cyclophosphamide, mycophenolate mofetil, azathioprine.

Results
LN patients were classified according to the baseline renal biopsies as patients with: minimal mesangial LN (4), mesangial-proliferative LN (30), focal proliferative LN (31), diffuse proliferative LN (48), membranous LN (44). aPL antibodies were detected in 89 (56,69%) patients, aCL antibodies – in 72 (45,86%), anti-β2-GPI antibodies – in 58 (36,94%) and LAC were detected in 46 (29,30%) patients. None of these patients had a concomitant diagnosis of antiphospholipid syndrome nephropathy. Follow-up was similar between aPL-positive and aPL-negative patients.
LN patients with positive aPL antibodies had significantly higher SLEDAI (p &lt; 0,05), anti-dsDNA levels (p &lt; 0,05), anti-ribosomal-P antibodies levels (p &lt; 0,05), anti-C1q antibodies (p &lt; 0,05), lower serum C3 (p &lt; 0,005) and C4 (p &lt; 0,05) levels, and higher intensity of complement C3 (p &lt; 0,05) deposits in kidney tissue than the aCL antibody–negative LN patients. aPL-seropositivity was associated with more rapid decline in eGFR (–1,06 mL/min/year compared to –0,45 mL/min/year in aPL-seronegative patients) and showed inferior patient survival (89,8% and 67,9% at 10 and 15 years, respectively, compared to 97,3% and 76% in aPL-seronegative patients). No significant correlation was found between serum aPL antibodies levels and activity or chronicity index scores in renal biopsies at baseline, ANA levels, or age.

Conclusion
We concluded that aPL-seropositivity are correlated with clinical activity in patients with LN and are associated with inferior long-term patient survival.