Two types of myeloperoxidase-antineutrophil cytoplasmic autoantibodies with a high affinity and a low affinity in small vessel vasculitis.
OBJECTIVE
Myeloperoxidase (MPO) -anti-neutrophil cytoplasmic autoantibodies (ANCAs) are detected at a high rate in microscopic polyangiitis and renal-limited vasculitis. MPO-ANCA titers are not always reflected in the disease activity. We studied the titer and affinity of MPO-ANCA in sera from patients in relation to vasculitis activity.


METHODS
Blood samples were collected from 27 newly diagnosed or relapsed patients with MPO-ANCA-associated vasculitides. The MPO-ANCA titer was determined by a direct enzyme-linked immunosorbent assay (ELISA) using homogeneously purified human MPO of leukocytes. The MPO-ANCA affinity was expressed as IC50 that was determined by a competitive inhibition method using the ELISA.


RESULTS
The MPO-ANCA affinity of 27 sera from 27 patients could be classified into a high-affinity type (14 sera) and a low-affinity type (13 sera). The mean values for IC50 in the two types were 0.15+/-0.06 microg/ml and 0.54+/-0.15 microg/ml, and the difference was statistically significant (p<0.0000000684). Between the two groups of patients divided by the affinity, there were differences in the Birmingham Vasculitis Activity Score (BVAS): and in C-reactive protein (CRP): (p<0.00093 and p<0.00129, respectively). However, the difference in titer was not statistically significant (p<0.0265). The affinity remained steady from the disease onset to remission or relapse.


CONCLUSIONS
The affinity of MPO-ANCA from patients with MPO-ANCA-associated vasculitides were largely distinguished into a high and a low affinity, irrespective of the level of MPO-ANCA titers, and may be helpful for assessment of vasculitis activity affecting mainly the kidney and the lung.
Yoshida
M
M
Renal Unit of Internal Medicine, Hachioji Medical Center, Tokyo Medical University, Japan. myoshida@tokyo-med.ac.jp
Sasaki
M
M
Nakabayashi
I
I
Akashi
M
M
Tomiyasu
T
T
Yoshikawa
N
N
Kojima
T
T
Ohno
N
N
Yamada
M
M
D000368:Aged; D000369:Aged, 80 and over; D056648:Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / Q000276:immunology* / Q000473:pathology / Q000503:physiopathology; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D000915:Antibody Affinity / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005921:Glomerulonephritis / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D054988:Idiopathic Interstitial Pneumonias / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D007676:Kidney Failure, Chronic / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D007962:Leukocytes / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D009195:Peroxidase / Q000276:immunology* / Q000378:metabolism; D012128:Respiratory Distress Syndrome / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D012720:Severity of Illness Index
D019268:Antibodies, Antineutrophil Cytoplasmic; D009195:Peroxidase