The Prevalences and Clinical Characteristics of Anti-Neutrophil Cytoplasmic Antibodies(ANCAs) in Lupus Nephritis(LN)

Chin, Ho Jun; Ahn, Curie; Lim, Chun Soo; Park, In Suk; Chung, Hee Kyoung; Song, Yong Wook; Lee, Hyun Soon; Han, Jin Suk; Kim, Suhnggwon; Lee, Jung Sang

Abstract

To elucidate the prevalence and clinical implications of antineutrophil cytoplasmic antibody(ANCA) in lupus nephritis(LN), we examined ANCA by indirect immunofluorescence and by ELISA against anti-MPO antibody and anti-lactoferrin antibody. To discriminate pANCA with antinuclear antibody(ANA), all the ANCA positive sera were tested again after incubating patients' sera with single stranded(ss) and double stranded(ds) DNA. To exclude possible cross-reactivity of anti-MPO antibody with lactoferrin, we also performed anti-MPO ELISA with sera preincubated with lactoferrin. These results were correlated with clinicopathologic manifestations and clinical courses of LN. ANCA was positive in 19(37.3%) out of the 51 LN patients. Among these LN patients, 3 had cANCA and 16 had pANCA. ANCA were not found in 8 SLE patients without nephritis and 30 normal controls. The presence of ANCA, particularly pANCA, was associated with the presence of nephritis(19/51 cases vs 0/8 cases, P<0.05), especially diffuse proliferative lupus nephritis(WHO class IV)(17/18 cases vs 21/31 cases, P<0.05) as well as the presence of anti-ds DNA antibody(17/19 cases vs 18/30 cases, P<0.05). Patients with ANCA more frequently had deterioration of renal function than those without it(3/16 vs 0/26 cases). Anti-lactoferrin antibody was positive in 13 patients. Among those, 5 didn't have ANCA, 7 had pANCA, and 1 had cANCA. The presence of anti-lactoferrin antibody was correlated to the low initial creatinine level[serum creatinine(mg/dl):0.78(0.6-1.0) vs 1.43(0.5-5.0), P<0.05]. Anti-MPO antibody was positive in one patient with cANCA and 6 patients with pANCA. However, in 6 patients, the anti-MPO activity was inhibited if tested after preincubation of the serum with lactoferrin. These data suggested that compared with lactorerrin, MPO is a rare antigen for ANCA in LN.