ANTINEUTROPHIL CYTOPLASMIC AUTOANTIBODIES (ANCA) AND THEIR TARGET ANTIGENS IN CHINESE PATIENTS WITH LUPUS NEPHRITIS

Background. ANCA have been found in patients with systemic lupus eryth ematosus (SLE); however, the prevalence of ANCA and their target antig ens is still not certain. This study is to investigate the prevalence of ANCA and their target antigens in Chinese patients with lupus nephr itis. Methods. Ninety-five serum samples were collected from 95 renal- biopsy-proven lupus nephritis patients. Indirect immunofluorescence us ing ethanol-fixed leukocytes as substrate and ELISA using six highly p urified known ANCA antigens as solid-phase ligands were performed. The specific ANCA antigens included proteinase 3, myeloperoxidase, bacter icidal/permeability-increasing protein, human leukocyte elastase, cath epsin G, and lactoferrin. The prevalence of ANCA in patients with (n = 65) and without (n = 30) active renal pathological lesions was also c ompared to reveal whether ANCA correlates with disease activity. Resul ts. (i) None of the sera recognized proteinase 3, myeloperoxidase, and human leukocyte elastase, and only one serum recognized bactericidal/ permeability-increasing protein. The striking finding was that 59/95 ( 62.1%) sera recognized cathepsin G and the titres of some sera reached 1/3200. Eight of 95 sera (8.4%) recognized lactoferrin. (ii) The perc entage of anticathepsin G antibody positive samples in patients with a ctive renal lesions was significantly higher than in patients without active lesions (73.4 vs 36.7%, P < 0.0001), whereas, anti-lactoferrin antibodies had no correlation with active renal lesions. (iii) By indi rect immunofluorescence, only 22% of the 95 sera were ANCA positive. C onclusions. Our results suggest that the majority of lupus nephritis p atients have ANCA and that the major target antigens is cathepsin G. A nti-cathepsin G antibodies seem to be correlated with renal disease ac tivity.