Figure 1. Renal biopsy findings for a PMN/IgAN patient. Immunofluorescence showing IgG (A) and IgG4 (B) in granular pattern. Immunofluorescence showing IgA (C) deposition in mesangial along with capillary area. Light microscopy showing glomerular basement membrane thickening and fuchsinophilic proteins in mesangial region (D,E). Electron micrograph showing subepithelial and mesangial electron-dense (F). (A–C: Original magnification ×200; D,E: Original magnification ×400; F: Original magnification ×5000).

Figure 1. Renal biopsy findings for a PMN/IgAN patient. Immunofluorescence showing IgG (A) and IgG4 (B) in granular pattern. Immunofluorescence showing IgA (C) deposition in mesangial along with capillary area. Light microscopy showing glomerular basement membrane thickening and fuchsinophilic proteins in mesangial region (D,E). Electron micrograph showing subepithelial and mesangial electron-dense (F). (A–C: Original magnification ×200; D,E: Original magnification ×400; F: Original magnification ×5000).

Figure 2. Flowchart of the recruitment process.

Figure 2. Flowchart of the recruitment process.

Figure 3. Representative images of immunofluorescence staining for KM55 in patients with PMN/IgAN, (A) Negative, (B) 1+ intensity, (C) 2+ intensity, (D) 3+ intensity. Positive staining of KM55 3+ (F) by immunofluorescence along the glomerular mesangial and capillary area in the same section with IgA positive staining (E). (G) KM55 and IgA colocalized completely along the glomerular mesangial and capillary area. The corresponding two-dimensional (2D) fluorograms have been included to confirm the degree of co-localization (H: Pearson’s correlation 0.9182, Overlap coefficient 0.9245;). (A–G: original magnification ×200).

Figure 3. Representative images of immunofluorescence staining for KM55 in patients with PMN/IgAN, (A) Negative, (B) 1+ intensity, (C) 2+ intensity, (D) 3+ intensity. Positive staining of KM55 3+ (F) by immunofluorescence along the glomerular mesangial and capillary area in the same section with IgA positive staining (E). (G) KM55 and IgA colocalized completely along the glomerular mesangial and capillary area. The corresponding two-dimensional (2D) fluorograms have been included to confirm the degree of co-localization (H: Pearson’s correlation 0.9182, Overlap coefficient 0.9245;). (A–G: original magnification ×200).

Figure 4. Comparison of the level of serum IgA (A) and Gd-IgA1 (B) between KM55+ and KM55− subgroup in PMN/IgAN patients. (A) The level of serum IgA in KM55+ subgroup was higher than KM55− subgroup in PMN/IgAN patients. (B) There was no significant difference in the level of serum Gd-IgA1 in KM55+ subgroup and KM55− subgroup, similar to the PMN/IgA deposition group.

Figure 4. Comparison of the level of serum IgA (A) and Gd-IgA1 (B) between KM55+ and KM55− subgroup in PMN/IgAN patients. (A) The level of serum IgA in KM55+ subgroup was higher than KM55− subgroup in PMN/IgAN patients. (B) There was no significant difference in the level of serum Gd-IgA1 in KM55+ subgroup and KM55− subgroup, similar to the PMN/IgA deposition group.

Figure 5. Positive staining for glomerular PLA2R (A), NELL-1 (B) and THSD7A (C) by immunohistochemistry, respectively. (Original magnification ×400).

Figure 5. Positive staining for glomerular PLA2R (A), NELL-1 (B) and THSD7A (C) by immunohistochemistry, respectively. (Original magnification ×400).

Figure 6. Kaplan-Meier analysis. Cumulative poor event-free renal survival rate between the KM55+ and KM55− subgroups.

Figure 6. Kaplan-Meier analysis. Cumulative poor event-free renal survival rate between the KM55+ and KM55− subgroups.

Table 1. Demographics and clinical features of patients with PMN/IgAN and PMN/IgA deposition.

Table 1. Demographics and clinical features of patients with PMN/IgAN and PMN/IgA deposition.

CharacteristicsPMN/IgAN
(n = 85)PMN/IgA Deposition
(n = 132)p Valuemale n (%)58 (68.2)85 (64.4)0.560Age (year)46.3 ± 14.748.5 ± 12.90.267duration of illness (month)3.0 (1.0, 10.5)3.0 (1.0, 8.0)0.766hypertension n(%)33 (38.8)61 (46.6)0.262microscopic hematuria n(%)44 (51.8)64 (48.9)0.676Proteinuria (g/24h)5.0 (2.9, 8.8)5.2 (3.5, 8.0)0.547serum albumin (g/L)27.4 (22.4, 33.5)25.9 (21.2, 29.6)0.049nephrotic syndrome n (%)53 (62.4)102 (77.3)0.018serum creatinine (μmol/L)70.4 (54.6, 84.4)66.0 (56.0, 79.2)0.297eGFR-EPI (ml/min/1.73 m2)104.0 (89.6, 116.7)102.6 (89.9, 114.6)0.901triglycerides (mmol/L)2.1 (1.4,2.8)2.1 (1.4, 3.4)0.296total cholesterol (mmol/L)6.7 (5.3, 7.9)7.0 (5.7, 9.0)0.071LDL-C (mmol/L)4.1 (2.9, 5.1)4.4 (3.3, 6.1)0.091uric acid (μmol/L)378.7 ± 85.9358.9 ± 84.60.104serum IgA (g/L)2.5 (1.8, 3.4)2.1 (1.6, 2.9)0.015serum IgG (g/L)6.7 (5.0, 9.2)5.7 (3.9, 7.4)0.004serum IgM (g/L)0.9 (0.6, 1.3)1.0 (0.7, 1.3)0.110serum C3 (g/L)1.2 ± 0.31.2 ± 0.20.094serum C4 (g/L)0.3 (0.2, 0.4)0.3 (0.2, 0.4)0.952

Table 2. Pathological features of patients with PMN/IgAN and PMN/IgA deposition.

Table 2. Pathological features of patients with PMN/IgAN and PMN/IgA deposition.

Pathological FeaturesPMN/IgAN
(n = 85)PMN/IgA Deposition
(n = 132)p ValueChurg stage of MN 0.019stage I n (%)31 (36.5)33 (25.0) stage II n (%)37 (43.5)83 (62.9) stage III n (%)16 (18.8)16 (12.1) stage IV n (%)1 (1.2)0 (0) glomerular IgG positive n (%)85 (100)132 (100)-glomerular IgG1 positive n (%)34 (40.5)66 (50.4)0.155glomerular IgG2 positive n (%)9 (10.7)12 (9.2)0.708glomerular IgG3 positive n (%)18 (21.4)18 (13.7)0.141glomerular IgG4 positive n (%)76 (90.5)127 (96.9)0.065glomerular IgG4 predominant positive n (%)72 (85.7)122 (93.1)0.074glomerular IgM positive n (%)25 (29.4)20 (15.2)0.011glomerular C1q positive n (%)7 (8.2)4 (3.0)0.115glomerular C3 positive n (%)74 (87.1)106 (80.3)0.196interstitial fibrosis,%, n (%) 0.678<2573 (85.9)117 (88.6) 25–5010 (11.8)14 (10.6) 50–752 (2.4)1 (0.8) >750 (0)0 (0)

Table 3. Disease-specific pathogenic biomarkers for patients with PMN/IgAN.

Table 3. Disease-specific pathogenic biomarkers for patients with PMN/IgAN.

CharacteristicsPMN/IgAN
(n = 85)PMN/IgA Deposition (n = 132)p Valueserum anti-PLA2R (RU/mL)8.2 (0.0, 46.1)47.1 (6.6, 118.3)<0.001positive rates of anti-PLA2R n (%)37 (43.5)81 (61.4)0.010glomerular PLA2R positive n (%)65 (76.5)130 (98.5)<0.001glomerular KM55 staining mesangial KM55 positive n (%)20 (23.5)0/29 (0)0.0041+8 (9.4)0 (0) 2+10 (11.8)0 (0) 3+2 (2.4)0 (0) mesangial KM55 negative n (%)65 (76.5)29/29 (100)

Table 4. Demographics and clinical features in PMN/IgAN patients based on the staining of glomerular KM55.

Table 4. Demographics and clinical features in PMN/IgAN patients based on the staining of glomerular KM55.

CharacteristicsKM55+
(n = 20)KM55−
(n = 65)p Valuemale n (%)14 (70.0)44 (67.7)0.846Age (year)47.3 ± 13.246.0 ± 15.20.722duration of illness (month)3.5 (1.0, 21.8)2.0 (1.0, 7.0)0.138hypertension n (%)12 (60.0)21 (32.3)0.026microscopic hematuria n (%)9 (45.0)35 (53.8)0.489Proteinuria (g/24h)3.8 (2.2, 6.3)5.8 (3.0, 9.3)0.040serum albumin (g/L)28.5 (23.0, 33.1)27.3 (22.3, 34.2)0.562nephrotic syndrome n (%)12 (60.0)41 (63.1)0.708serum creatinine (μmol/L)75.0 (58.8, 85.2)68.8 (54.0, 80.2)0.242eGFR-EPI (ml/min/1.73 m2)99.9 (81.8, 112.1)104.4 (91.4, 118.1)0.325triglycerides (mmol/L)2.2 (1.5, 3.7)2.0 (1.3, 2.7)0.357total cholesterol (mmol/L)6.6 (5.5, 7.1)6.7 (5.1, 8.0)0.713LDL-C (mmol/L)3.5 (3.0, 4.4)4.4 (2.9, 5.6)0.168uric acid (μmol/L)389.7 ± 77.0375.1 ± 88.90.510serum IgA (g/L)3.2 (2.4, 3.9)2.2 (1.7, 3.2)0.026serum IgG (g/L)7.1 (4.6, 8.1)6.5 (5.0, 9.7)0.782serum IgM (g/L)0.8 ± 0.51.0 ± 0.40.192serum C3 (g/L)1.2 ± 0.21.2 ± 0.30.719serum C4 (g/L)0.3 (0.3, 0.4)0.3 (0.2, 0.3)0.095

Table 5. Pathological features in PMN/IgAN patients based on the staining of glomerular KM55.

Table 5. Pathological features in PMN/IgAN patients based on the staining of glomerular KM55.

Pathological FeaturesKM55+
(n = 20)KM55−
(n = 65)p ValueChurg stage of MN 0.017stage I n (%)2 (10.0)29 (44.6) stage II n (%)13 (65.0)24 (36.9) stage III n (%)5 (25.0)11 (12.2) stage IV n (%)0 (0)1 (0.8) glomerular IgG positive n (%)20 (100)65 (100)-glomerular IgG1 positive n (%)5 (25.0)29/64 (45.3)0.106glomerular IgG2 positive n (%)1 (5.0)8/64 (12.5)0.679glomerular IgG3 positive n (%)5 (25.0)13/64 (20.3)0.756glomerular IgG4 positive n (%)18 (90.0)58/64 (90.6)1.000glomerular IgG4 predominant positive n (%)18 (90.0)54/64 (84.4)0.722glomerular IgM positive n (%)5 (25.0)20 (30.8)0.620glomerular C1q positive n (%)0 (0)7 (10.8)0.191glomerular C3 positive n (%)17 (85.0)57 (87.7)0.715interstitial fibrosis,%, n (%) 0.009<2518 (90.0)55 (84.6) 25–500 (0)10 (15.4) 50–752 (10.0)0 (0) >750 (0)0 (0)

Table 6. Disease-specific pathogenic biomarkers in PMN/IgAN patients based on the staining of glomerular KM55.

Table 6. Disease-specific pathogenic biomarkers in PMN/IgAN patients based on the staining of glomerular KM55.

CharacteristicsKM55+
(n = 20)KM55−
(n = 65)p Valueserum anti-PLA2R (RU/mL)15.3 (0.5, 76.3)5.9 (0, 39.4)0.241positive rates of anti-PLA2R n (%)9 (45.0)28 (43.1)0.879glomerular PLA2R positive n (%)17 (85.0)48 (73.8)0.379glomerular PLA2R negative n (%)3 (15.0)17 (26.2) glomerular 7A positive n (%)0(0)1 (5.9) glomerular NELL-1 positive n (%)2 (66.7)1 (5.9) serum Gd-IgA1 (ug/mL) *4.3 ± 1.44.9 ± 2.80.332

Table 7. Follow-up data in PMN/IgAN patients based on the staining of glomerular KM55.

Table 7. Follow-up data in PMN/IgAN patients based on the staining of glomerular KM55.

CharacteristicsKM55+
(n = 14)KM55−
(n = 26)p Valueremission n (%)9 (64.3)19 (73.1)0.720complete remission n (%)4 (28.6)6 (23.1)0.718partial remission n (%)5 (35.7)13 (50.0)0.386immunosuppressive therapy n (%)14 (100.0)23 (88.5)0.539prednisone and cyclosporin remission n (%)2/3 (66.7)3/5 (60.0)1.000cyclosporin remission n (%)5/7 (71.4)9/12 (75.0)1.000other remission n (%)2/4 (50.0)5/6 (83.3)0.500composite outcome n (%)5 (35.7)1 (3.8)0.014