[Antigens of antineutrophil cytoplasmic autoantibodies in recognizing a novel neutrophil granule antigen in lupus nephritis and its association with photosensitivity and oral ulceration].
OBJECTIVE
To investigate whether there are some unknown target antigens of antineutrophil cytoplasmic autoantibodies (ANCA) in patients with lupus nephritis (LN) and the prevalence and the clinical significance of these unknown target antigens.


METHODS
Serum was collected from 72 renal-biopsy-proven lupus nephritis (LN) patients. Mixed neutrophil granules were separated from normal human peripheral neutrophils and soluble acid extracts in non-reducing conditions were used as antigens in Western-blot analysis to detect ANCA in the serum sample of LN patients.


RESULTS
Serum from seme LN patients could blot a few bands. Interestingly, serum from 14/72 (19.4%) of the patients recognized a novel 69,000 protein band and that from 10/72 (13.9%) sera recognized a 55,000 protein band that might be the bactericidal/permeability-increasing protein (BPI). The 69,000 target antigen was different from the known target ANCA antigens such as cathepsin G and lactoferrin. Further study revealed that the percentages of patients with photosensitivity and oral ulcer in anti-69,000 autoantibody positive group were significantly higher than those in the anti-69,000 autoantibody negative group (57.1% vs 12.1%, P < 0.005, and 50.0% vs 17.2%, P < 0.05, respectively).


CONCLUSIONS
A novel 69,000 protein in human neutrophil granules is identified as a target antigen of ANCA in LN patients. The anti-69,000 autoantibodies may be associated with photosensitivity and oral ulcer in LN patients.
Chen
Min
M
Renal Division, The First Hospital & Institute of Nephrology, Peking University, Beijing 100034, China.
Zhao
Minghui
M
Zhang
Youkang
Y
Wang
Haiyan
H
D000293:Adolescent; D000328:Adult; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology; D001324:Autoantigens / Q000276:immunology*; D003594:Cytoplasmic Granules / Q000276:immunology; D005260:Female; D006801:Humans; D008181:Lupus Nephritis / Q000276:immunology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000276:immunology*; D019226:Oral Ulcer / Q000276:immunology*
D019268:Antibodies, Antineutrophil Cytoplasmic; D001323:Autoantibodies; D001324:Autoantigens