Assessments for IgA anti-GBM were not available on admission. (IgG), immunoglobulin A (IgA), 3(IV) collagen chain Introduction Anti-glomerular basement membrane (anti-GBM) disease is usually a rare autoimmune condition responsible for rapidly progressive glomerulonephritis, which is usually mediated by circulating autoantibodies. The principal autoantigen is the 345 network of collagen IV, expression of which is usually restricted to target tissues . Typically, linear deposition of immunoglobulin along the glomerular basement membrane (GBM) is seen. In most Gallic Acid cases, the causative antibody is usually IgG [2,3]. Rarely, however, anti-GBM disease is usually mediated by immunoglobulin A (IgA) or immunolgobulin M (IgM) antibodies [4C7]. Here, we describe a new case of anti-GBM disease mediated by immunolgobulin G (IgG) and IgA. Case report A 37-year-old woman was admitted to the renal unit for rapidly progressive glomerulonephritis. Medical history included fracture of the left clavicle 10?years ago. She has no smoking or alcohol, no history of hydrocarbon exposure, chemicals or heavy metal exposure, etc. The results of physical examination on admission, including blood pressure (110/65?mmHg), were normal. Serum creatinine had risen from 72?mol/L to 310?mol/L over the past 2?weeks. Urinary examination disclosed microscopic hematuria and proteinuria within the nephrotic range (8.11?g/day). She had hypoproteinemia (albumin 24?g/L) with no anemia (hemoglobin 124?g/L). Routine ELISAs were positive for anti-GBM (104?RU/mL, normal range <20?RU/mL) (EA 1251-9601?G; Euroimmun Medizinische Labordiagnostika (China), Beijing, China). Assessments for IgA anti-GBM were not available on admission. Other laboratory investigations showed normal C3 and C4 levels and unfavorable anti-nuclear antibody, anti-phospholipid antibody, and anti-neutrophil cytoplasmic antibody (ANCA). Immunoglobulins G, M, and A were normal and no paraprotein was found in serum or urine. Ultrasound showed normal kidneys. Computed tomography (CT) excluded alveolar hemorrhage. Kidney biopsy was performed. Immunofluorescence analysis indicated bright capillary wall staining for IgA (2+ to 3+) (Physique 1(A)) and IgG (2+ to 3+) (Physique 1(B)). There was weakly capillary wall staining for , and (+), and segmental staining for IgM (1+) and FRA (2+). C3, C1q, HbsAg, HbcAg, and HCV-Ag were negative. All the four IgG subclassed deposition along GBM were detected. There was bright capillary wall staining for IgG1 (2+ to 3+) and IgG3 (2+), and PTGER2 weakly capillary wall staining for IgG2 (+) and IgG4 (+). Light microscopy showed segmental fibrinoid necrosis in five of 36 glomeruli (Physique 1(C,D)), and fibrinoid necrosis with crescent formation in seven of 36 glomeruli (Physique 1(E)). Epithelial cell foot process fusion was present, and no electron-dense deposits were found Gallic Acid by electron microscopy (Physique 1(F)). The findings of renal biopsy suggested anti-GBM disease. Open in a separate window Physique 1. Diagnosis of anti-GBM disease mediated by IgG and IgA in the renal biopsy specimen. (A) Direct immunofluorescence analysis showed strong (2+ to 3+) linear capillary loop IgA (original magnification, 200). (B) Direct immunofluorescence analysis showed strong (2+ to 3+) linear capillary loop IgG (original magnification, 200). (C) Light microscopy showed segmental fibrinoid necrosis (PASM, 200). (D) Light microscopy showed segmental fibrinoid necrosis (PASM, 400). (E) Light microscopy showed fibrinoid necrosis with crescent formation (PASM, 200). (F) Epithelial cell foot process fusion was detected, and no electron-dense deposits were found on electron microscopy (original magnification, 5000). Informed consent was obtained for analysis of the patients serum. One human serum sample was used as a negative control, and another serum sample from an IgG anti-GBM patient was used as a positive control. Human kidney cortex basement membranes and non-collagenous (NC1) hexamers of type IV collagen were prepared as described previously [8C11]. Another commercial ELISA kit (EA 1251-9601?G; Euroimmun Medizinische Labordiagnostika (China), Beijing, China) using bovine kidney 3 (IV) collagen NC1 domain name as an antigen was used to Gallic Acid detect the presence of IgG anti-GBM autoantibodies in the patients serum. The recombinant human 3 (IV)NC1 (2?g/L) were coated into the 96-well plates at 4?C overnight. After blocking and washing, diluted blood samples (1:100) were added at 37?C for 60?min. After washing, horseradish peroxidase (HRP)-conjugated mouse anti-human IgA antibodies (Sigma-Aldrich, St. Louis, MO) diluted at 1:5000 were added at 37?C for 60?min. 3,3,5,5-Tetramethylbenzidine (TMB) liquid was applied as substrate and the color development was terminated by 1?mM sulfuric acid after 20?min. The plates were read at 450?nm and absorbance value Gallic Acid Gallic Acid of each sample was calculated. The patients serum contained IgA (82?RU/mL, normal range <20?RU/mL) and IgG (78?RU/mL, normal range <20?RU/mL) anti-GBM autoantibodies. Further analysis was performed by Western blotting.