Abstract: Ｏｂｊｅｃｔｉｖｅ：To explore the correlation between anti-angiotensin Ⅱ Type 1 receptor antibody (AT1R-AA) and clinicopathological characteristics of patients with lupus nephritis (LN).
Ｍｅｔｈｏｄｏｌｏｇｙ：98 patients with active LN confirmed by renal biopsy were evaluated for lupus activity using SLE-DAI. Renal tissue activity index (AI) and chronicity index (CI) were semi-quantitatively scored. Serum AT1R-AA was detected by ELISA (>17 U／mL defined as positive). Involvement of 3 or more other systems due to lupus activity was defined as multi-system involvement. According to whether AT1R-AA and anti-dsDNA or anti-C1q antibodies were simultaneously positive, they were divided into two groups: single positive and double positive antibodies. 18 healthy individuals matched for gender and age with LN patients were selected as normal controls. AT1R-AA was retested in 14 patients who achieved remission after immunosuppressive therapy.
Ｒｅｓｕｌｔｓ：The median SLE-DAI score of 98 LN patients was 13 (10,16), nearly half had multi-system involvement, and the median serum AT1R-AA level in LN patients was significantly higher than that in the normal control group (17.6 U／mL vs 7.93 U／mL, P<0.001). 51％ of patients had positive serum AT1RAA, and there were no difference in AT1R level and positivity rate among different pathological types. Correlation analysis showed that AT1R-AA level was positively correlated with SLE-DAI (r=0.490, P<0.001) and negatively correlated with C3 (r=-0.279, P=0.005) and C4 (r=-0.270, P=0.007) levels. Compared with AT1R-AA negative patients, AT1R-AA positive patients had significantly higher SLE-DAI scores (P<0.001), number of organ systems involved (P<0.001), and proportion of multiorgan system damage (P<0.001), significantly decreased serum C3 levels (P=0.021) and CI scores (P=0.049), and no significant difference in renal injury indicators between the two groups. Compared with the single antibody positive group, the double antibody positive group had significantly higher SLE-DAI scores (P<0.001), multiorgan system involvement (P=0.037), and acute kidney injury ratio (P=0.016), while serum C3 (P=0.021) and C4 (P=0.022) levels were significantly lower. After treatment, the serum AT1R-AA level (22.9 U/mL vs 12.4 U/mL, P=0.001) and positivity rate (78.6％ vs 21.4％, P=0.008) of 14 patients who achieved renal remission were significantly reduced.
Ｃｏｎｃｌｕｓｉｏｎ：AT1R-AA is a new serological marker for active lupus nephritis patients, which is correlated with SLE-DAI score and system involvement. Lupus activity, organ system involvement and renal injury degree are significantly increased in patients with co-positive AT1R-AA and anti-dsDNA or anti-C1q antibodies.