Anti-neutrophil cytoplasmic antibodies (ANCA) in systemic lupus erythematosus: prevalence, clinical associations and correlation with other autoantibodies.

Aim: This study was undertaken to clarify the nature of anti-neutrophil cytoplasmic antibodies (ANCA) along with other autoantibodies in lupus nephritis (LN) patients and in systemic lupus erythematosus (SLE) patients without nephritis and to know their correlation with clinical manifestations and presence of other autoantibodies.

Material And Methods: Fourty one LN patients and 18 SLE patients without nephritis were studied. LN patients were subdivided into diffuse proliferative glomerulonephritis (DPGN), focal proliferative glomerulonephritis (FPGN), rapidly progressive glomerulonephritis (RPGN) and membranoproliferative glomerulonephritis (MPGN). Anti-neutrophil cytoplasmic antibodies (ANCA) were detected by indirect immunofluorescence and confocal laser scanning microscope using PMN and HL60 cells. ANCA specificities like anti-myeloperoxidase (anti-MPO), anti-proteinase 3 (anti-PR3), anti-lactoferrin (anti-LF) and anti-cathepsin G (anti-CG) were detected by ELISA. Other autoantibodies like anti-nuclear antibodies (ANA), anti-double stranded DNA (anti-dsDNA), anti-single stranded DNA(anti-ssDNA), anti-ribonucleoproteins (anti-nRNP), anti-Smith antibodies (anti-Sm) and rheumatoid factor (RF) were also tested.

Results: ANCA was detected in 37.3% patients. The predominant ANCA pattern was perinuclear (p-ANCA). ANCA positivity was higher in LN patients and when confirmed by ELISA, 54.5% ANCA positives had anti-myeloperoxidase (anti-MPO). The cytoplasmic ANCA (c-ANCA) pattern was not seen in any patient. Two patients having FPGN with crescents showed atypical 'X-ANCA' pattern with dual specificity to anti-MPO and anti-PR3 by ELISA. The titers of ANCA were more in LN as compared to SLE without nephritis. LN cases having DPGN, FPGN, RPGN with crescents had higher titer p-ANCA positivity with corresponding anti-MPO antibodies, along with ANA, anti-dsDNA, anti-ssDNA and anti-Sm + anti-nRNP and also high SLEDAI scores.

Conclusion: ANCA in SLE may be used as a serological marker along with clinical and histopathological assessment to differentiate vasculitides in LN cases from SLE without nephritis.