Lin Duan's research while affiliated with Peking Union Medical College Hospital and other places

Background: The role of IgG subclass in idiopathic membranous nephropathy (IMN) was unclarified. Recent study found IgG subtype switches from IgG1 to IgG4 in the early pathological stage in IMN. The profile of IgG subclass in phospholipase A2 receptor- (PLA2R-) related and PLA2R-unrelated IMN was unrevealed. Our study is aimed at testifying whether IgG subclass switch existed in PLA2R-related and PLA2R-unrelated IMN, respectively. Methods: Our study retrospectively enrolled 157 Chinese patients with biopsy-confirmed IMN between September 2017 and November 2019. We measured glomerular PLA2R antigen and serum anti-PLA2R antibody to classify the patients into PLA2R-related (n = 132) and PLA2R-unrelated (n = 25) subgroup. We evaluated glomerular IgG subclass by immunofluorescence (IF) predominance. Our study defined IgG subclass deposition as predominant if the IF score was higher than the other three and ≥1 +, or as codominant if the IF intensity was equal to any other and ≥1 +. We explored the relationship between IF predominance of glomerular IgG subtype and electron microscopic (EM) stages of IMN. Results: We did not find statistical difference of predominant or codominant rate (pre/co-rate) among EM stages in any subclass (P > 0.05). Pre/co-rate of IgG3 linearly associated with EM stage in total and PLA2R-related subgroup (P = 0.044, P = 0.013). PLA2R-related subgroup showed higher IgG4 intensity (2.1 ± 0.6 vs. 1.6 ± 0.7, P = 0.001) and pre/co-rate of IgG4 in stage 1 (97% vs. 57%, P = 0.015) than PLA2R-unrelated group. We found no difference of IgG subclass pre/co-rate in different EM stages or linear association between pre/co-rate of IgG1, IgG2, IgG4, and EM stages (P > 0.05). Conclusions: Pre/co-rate of IgG3 declined with EM stage in total and PLA2R-related subgroup. We did not find IgG subclass switches from IgG1 to IgG4 in either IMN patients or subgroups.

Background and Aims Antibody to phospholipase A2 receptor (PLA2R) was widely detected for a decade as a diagnostic marker of idiopathic membranous nephropathy. Recently, several studies reported that a lower cut-off of serum PLA2R antibody (PLA2RsAb) could improve diagnostic efficacy. The recommend cut-off ranged from 2.0 to 2.7 RU/ml which was considered largely improving the sensitivity of the assay. Other reported that although sensitivity of the measurement might loss to some extent cut-off at 14 RU/ml might of the best clinical performance. However, the lower cut-off was slightly higher than the minimum detection limit, that was 2.0 RU/ml. There was no study evaluated the test efficiency of low titer antibody of the measurement. Method The reference range of PLA2RsAb was validated by testing 40 serum from health volunteer, male/female ratio was 20/20. The samples for intra and inter-batch precision test were prepared by mixing low titer PLA2RsAb serum. The intra-batch precision was performed by repeating six times of the validation sample in one plate. The inter-batch precision was performed by repeating four times of validation samples in one plate on five days. Results The medium age of male was 34 (31, 53) and 46 (31, 54) for female, respectively. PLA2RsAb was ranged from 2.0 to 4.3 RU/ml for male and 2.0 to 4.0 RU/ml for female. The average of intra-batch validation sample was 8.1 ± 1.2 RU/ml. The intra-batch precision was presented by coefficient of variation, that was 15%. The average of inter-batch validation samples were 4.0 ± 0.4 RU/ml and 5.2 ± 0.5 RU/ml, respectively. The inter-batch precision was 10% for both validation serum. Conclusion Healthy population showed low titer PLA2RsAb positive according to a lower cut-off. The validation showed relative high coefficient of variation on intra and inter-batch precision of low titer PLA2RsAb.

Background: To evaluate renal expression of C4d, a complement component in the classical/mannose binding lectin (MBL) pathway, in patients with primary Sjögren's syndrome (pSS)-associated renal impairments. Methods: We retrospectively reviewed the clinical and pathological data from 39 patients with pSS presenting with renal impairments. C4d was examined in paraffin-embedded biopsy tissues using immunohistochemistry. Glomerular C4d positive was defined when > 75% glomeruli were globally stained. Tubulointerstitial C4d (TI-C4d) were scored semi-quantitatively as 0 (absent), 1 (spotty or weak), 2 (patchy) and 3 (diffuse). A TI-C4d score ≥ 2 was considered TI-C4d positive and included in the TI-C4d+ group and vice versa. Peritubular capillary (PTC) C4d was scored as 0 (absent), 1 (0~10%, minimal), 2 (10%~ 50%, focal), and 3 (> 50%, diffuse). Results: Glomerular C4d deposition was observed in all 8 patients with pSS-related membranous nephropathy (MN) without obvious C1q deposition. Two of 5 patients with mesangial proliferative glomerulonephritis and 1 of 2 patients with IgA nephropathy had mild mesangial C4d deposition. Sixteen patients (6 glomerular dominant and 10 tubulointerstitial dominant) presented TI-C4d score ≥ 2. Patients in the TI-C4d+ group exhibited a higher serum creatinine level at the time of renal biopsy (TI-C4d+ 132.5 [89.7, 165.5] vs. TI-C4d- 83.0 [70.7, 102.0] μmol/L, P = 0.008). PTC C4d was observed in 12 patients, with each of minimal, focal and diffuse staining being noted in 4 patients. Conclusions: The MBL pathway of complement activation was potentially involved in pSS-related MN. Tubulointerstitial C4d might be a pathological marker of severe renal injury in patients with pSS-related renal impairments.

Objectives To evaluate renal expression of C4d, a complement component in the classical/mannose binding lectin (MBL) pathway, in patients with primary Sjögren’s syndrome (pSS)-associated renal impairments. Methods We retrospectively reviewed the clinical and pathological data from 39 patients with pSS presenting with renal impairments. C4d was examined in paraffin-embedded biopsy tissues using immunohistochemistry. Glomerular C4d positive was defined when >75% glomeruli were globally stained. Tubulointerstitial C4d (TI-C4d) were scored semi-quantitatively as 0 (absent), 1 (spotty or weak), 2 (patchy) and 3 (diffuse). A TI-C4d score ≥2 was considered TI-C4d positive and included in the TI-C4d ⁺ group and vice versa. Peritubular capillary (PTC) C4d was scored as 0 (absent), 1 (0∼10%, minimal), 2 (10%∼50%, focal), and 3 (>50%, diffuse). Results Glomerular C4d deposition was observed in all 8 patients with pSS-related membranous nephropathy (MN) without obvious C1q deposition. Two of 5 patients with mesangial proliferative glomerulonephritis and 1 of 2 patients with IgA nephropathy had mild mesangial C4d deposition. Sixteen patients (6 glomerular dominant and 10 tubulointerstitial dominant) presented TI-C4d score ≥2. Patients in the TI-C4d ⁺ group exhibited a higher serum creatinine level at the time of renal biopsy (TI-C4d ⁺ 132.5 [89.7, 165.5] vs. TI-C4d ⁻ 83.0 [70.7, 102.0] μmol/L, P=0.008). PTC C4d was observed in 12 patients, with each of minimal, focal and diffuse staining being noted in 4 patients. Conclusions The MBL pathway of complement activation was potentially involved in pSS-related MN. Tubulointerstitial C4d might be a pathological marker of severe renal injury in patients with pSS-related renal impairments.

Objective: To investigate the clinicopathological features and prognosis of idiopathic membranous nephropathy (IMN) in adolescents. Methods: This was a retrospective study on IMN patients hospitalized between June 2012 and December 2014, and a total of 33 IMN patients aged between 13 and 24 years old were enrolled in the study. Meanwhile, 33 IMN patients aged more than 24 years old were selected randomly as control group during the same period. Diagnosis was confirmed by renal biopsy, and the secondary causes of membranous nephropathy were ruled out. Data collected from medical record and biopsy were analyzed. Results: In the adolescent IMN group, the mean age at renal biopsy was (20 ± 3) years old, and the male/female ratio was 22/11. Twenty-three cases presented as nephrotic syndrome. Systolic and diastolic pressures were (127 ± 13) mmHg and (77 ±9) mmHg, respectively. The median 24-hour urine protein was 5.14 (3.39, 9.31) g/d, and the median serum creatinine was 62 (52, 73) μmol/L The positive rate of serum anti-phospholipase A2 receptor in adolescent group was 54%. Compared with control group, the adolescent patients had lower incidence of hypertension and higher baseline estimated glomerular filtration rate level [15.2% vs. 39.3%, χ² = 4.889, P = 0.03; 125 ml/(min · 1.73m²) vs. 100 ml/(min · 1.73m²), U = 137.5, P < 0.001]. According to IMN staging criteria in electron microscopy, adolescent patients were classified as one case in stage 1, 21 in stage II, and 11 in stage HI or higher. The positive rates of IgG1, IgG2, IgG3 and IgG4 subclass staining in glomeruli were 46.9%, 3.1%, 56.3%, and 87.5%, respectively. Compared with control group, the adolescent patients had lower incidence of renal interstitial fibrosis and arteriolar lesions (6.1% vs. 66.7%, χ² = 26.19, P < 0.001; 15.2% vs. 66.7%, χ² = 18.11, P < 0.001). Three patients lost to follow-up while others started steroid combined with cyclosporine A (n = 20), cyclophosphamide (n = 7), or mycophenolate (n = 1) or solely (n = 2). After a median follow-up of 18 (12, 24) months, the median proteinuria decreased to 0.20 (0.10, 0.42) g/d, whereas serum creatinine level remained stable [69 (56.8, 81.3) μmol/L]. Seventeen patients (56.7%) achieved complete remission (CR), and the remaining 13 patients (43.4%) achieved partial remission (PR). The median time of CR and PR were three and six months, respectively. Only one patient relapsed during the follow-up. Also, 21 cases received maintenance therapy including cyclosporine A (n = 18), azathioprine (n = 2) and mycophenolate (n = 1). Conclusions: The immunofluorescence IgG subclass in glomeruli and distribution of serum anti-phospholipase A2 receptor in adolescent IMN patients are similar to those in older IMN patients. IMN patients in adolescents responded well to immunosuppressive therapy. Cyclosporine A in low dose as maintenance therapy is effective after achieving remission, and will not increase risk of nephrotoxicity.