Immunohistochemical characterization of glomerular IgA deposits in IgA nephropathy

To characterize the IgA deposits found in glomeruli of IgA nephropathy, frozen sections of renal biopsy specimens from 191 consecutive patients with IgA nephropathy were examined by immunofluorescent microscopy. All 191 specimens were positive for IgA1 in glomeruli. IgA2 was detected in 3 out of these 191 specimens. Both kappa and lambda light chains were also detected in the glomeruli of all specimens. The presence of J chain was represented in 113 specimens after acid-urea pretreatment. Secretory component (SC) was detected in 13 out of the 191 specimens, but not in controls. Both J chain and SC were detected in 2 out of 3 specimens positive for IgA2 but not for IgM. These results suggest that IgA deposited in glomeruli in some patients with IgA nephropathy is perhaps mucosally derived IgA.     

Immunohistochemical analysis of extracellular components on the glomerular sclerosis in patients with glomerulonephritis and diabetic nephropathy

Immunofluorescence and immunoperoxidase staining were carried out to determine the correlations between the progression of glomerular sclerosis and changes in the amount and distribution of glomerular extracellular components, such as Type I, III, IV, V, VI collagen, laminin (LN) and fibronectin (FN) in patients with various types of glomerulonephritis and diabetic nephropathy. Six patients with IgA nephropathy, four patients with membrano-proliferative glomerulonephritis, four patients with rapidly progressive glomerulonephritis and six patients with diabetic nephropathy were examined. The intensity and distribution of Type IV collagen, LN and FN were similar between the glomeruli from normal individuals and patients with mild stages of glomerulonephritis and diabetic nephropathy. However, staining of Type I, III or V collagen was not observed in the glomeruli from normal individuals and such patients. In more advanced stages of glomerulonephritis and diabetic nephropathy, the amounts of Types IV and VI collagen, LN and FN were increased markedly in the mesangium, and their distribution extended along the glomerular capillary walls. The intensity of Type IV collagen, LN or FN in the nodular sclerotic lesions of glomeruli was decreased significantly in patients with glomerulonephritis and diabetic nephropathy. On the other hand, staining of Types I, III and V collagen was observed focally in the sclerotic or hyalinotic glomeruli and around such glomeruli in these patients. In light microscopic examinations, the patients who had marked staining of Type I, III or V collagen by immunofluorescence showed severe damage of the basement membrane in Bowman's capsules. It is concluded that hyperproduction and/or infiltration of interstitial collagens, i.e. Types I, III and V collagen, is closely linked to the progression of glomerular sclerosis and hyalinosis in patients with various types of glomerulonephritis and diabetic nephropathy.     

Immunohistochemical analysis of extracellular components in the glomerular sclerosis of patients with glomerulonephritis

Immunofluorescence and immunoperoxidase staining was carried out to determine correlations between the progression of glomerular sclerosis and changes in the amount or distribution of glomerular extracellular components, including type I, III, IV, and VI collagens, laminin and fibronectin, in patients with IgA nephropathy, membranoproliferative glomerulonephritis and rapidly progressive glomerulonephritis. Staining of type I and III collagens was not observed in glomeruli from normal individuals or patients with mild glomerulonephritis. In the advanced stages of glomerulonephritis, the staining of type IV and VI collagens, laminin and fibronectin was marked in the glomerular mesangium, and the distribution of fibronectin extended to the glomerular capillary walls in the sclerotic lesions of glomeruli. However, the staining intensity of type IV collagen, laminin and fibronectin was gradually decreased during the progression of glomerular sclerosis. On the other hand, the staining of type I and III collagens was observed focally in sclerotic or hyalinotic glomeruli and around such glomeruli in those patients. Light microscopic examination revealed that patients who showed marked staining of type I and III collagens by immunofluorescence had severe damage of Bowman's capsules. These results suggest that the hyperproduction and/or invasion of interstitial collagens, i.e., types I and III, are closely linked to the progression of glomerular sclerosis and hyalinosis in patients with various types of glomerulonephritis.     

Participation of complement components in glomerular deposition in IgA nephropathy

To clarify the role of complement components in glomerular deposition in IgA nephropathy, clinicopathological and immunohistological studies were performed on 299 patients (171 males and 128 females; age, 9-71 years). Glomerular IgA deposition with IgG and/or IgM was observed more frequently in patients with Clq and/or C4 than in those with only C3 deposition (P less than 0.001). Patients with glomerular deposition of Clq and/or C4 showed more severe proteinuria (1 g/24 hr less than), a lower glomerular filtration rate (GFR), a higher incidence of duplication of capillary walls and more severe proliferation of mesangial cells and an increase in mesangial matrix (P less than 0.05), as compared to those without both Clq and C4. Patients with glomerular C3 deposition had significantly lower serum CH50 levels at the time of renal biopsy (P less than 0.02) and a significantly higher incidence of sclerotic lesions (P less than 0.05). Patients with C3 deposition in the mesangium and peripheral capillaries had significantly higher serum IgA levels (P less than 0.02), a significantly higher incidence of adhesion (P less than 0.01), duplication and endocapillary proliferation (P less than 0.05) and a more severe increase in mesangial cells (P less than 0.01) than those with C3 deposition only in the mesangium. The above findings demonstrate that analysis of the complement system in glomeruli is important for the evaluation of glomerular damage, clinical findings and prognosis.     

Changes in the glomerular density and size in serial renal biopsies during the progression of IgA nephropathy

BACKGROUND: Although there have been many reports on clinicopathological studies of IgAN, information is limited regarding the long-term evolution of a renal histology by analysing samples obtained not only during normal renal function but also after the establishment of an impaired renal function in individual patients. METHODS: We analysed 18 pairs of serial biopsy specimens from 18 patients with IgA nephropathy (IgAN) in whom the first renal biopsies were performed while normal renal function was still present and the second biopsies were performed after impaired renal function was established. The glomerular density (GD, number of non-sclerotic glomeruli per renal cortical area) and mean glomerular area (MGA) were compared between the specimens. RESULTS: The GD at the first biopsy of each patient showed a striking variation (1.3-5.2/mm(2)). As a whole, the GD decreased (2.7 +/- 1.2 versus 1.4 +/- 0.7/mm(2)) and the MGA increased (19.7 +/- 4.2 x 10(3) versus 23.5 +/- 4.5 x 10(3) mm(2)) between the biopsies, respectively. The degrees of change in the GD and the MGA between the biopsies differed remarkably among the individuals. The patients with a high GD in the first biopsy progressed slowly, but showed a large decrease in the GD and a large increase in the MGA between the biopsies, respectively. The patients with a low GD, who already had enlarged glomeruli in the first biopsy, tended to progress rapidly. CONCLUSIONS: Our results suggest that both the nephron number and glomerular enlargement play a crucial role as compensatory mechanisms against renal functional deterioration in progressive IgAN. The GD during normal renal function may determine these compensatory changes and thereby make it possible to predict the renal prognosis in IgAN.     

Apoptotic cells in six patients with IgA nephropathy in repeat biopsies

SUMMARY: Programmed cell death is a selective process of physiological cell deletion and is known as apoptosis. The purpose of the present study was to determine the relationship between the existence of apoptotic cells in glomeruli and the clinical or histopathological findings obtained in repeat renal biopsies of patients with IgA nephropathy. Repeat renal biopsy specimens were obtained from six patients with IgA nephropathy. The nick end labelling method (TUNEL) was used for the detection of apoptotic cells. Clinical laboratory data, i.e. urinary protein excretion, creatinine clearance (Ccr), blood urea nitrogen (BUN) and serum creatinine, (s‐Cr) were obtained from these patients. At the first renal biopsy, apoptotic cells in the glomeruli were observed in three out of six patients using TUNEL. These patients were classified as the severe glomerular damage group. The other three patients without apoptotic cells were in the mild glomerular damage group. Mean levels of urinary protein excretion at the first renal biopsy in the patients with apoptotic cells were slightly higher than those in patients without apoptotic cells. Levels of Ccr in patients with apoptotic cells were lower than those in patients without apoptotic cells. There were no significant differences in the levels of BUN and s‐Cr in patients with or without apoptotic cells. Two patients with apoptotic cells in glomeruli at the first renal biopsy did not show apoptotic cells at the second renal biopsy. These two patients showed improvement not only in clinical laboratory findings but also in histological findings at the second biopsy. Only one patient with apoptotic cells at the first and second biopsies exhibited deterioration at the second biopsy. All three patients without apoptotic cells at the first renal biopsy also showed deterioration of the clinical laboratory and histopathological findings. It is postulated that various factors other than apoptosis might induce progression of renal injuries in such patients. It appears that the clinical laboratory data, i.e. proteinuria, renal function and histopathological findings, might be influenced by apoptosis in patients with IgA nephropathy. It is postulated that apoptosis may induce reduction of excess proliferative glomerular mesangial cells and/or infiltrating cells and tissue repair.     

Correlation between glomerular morphology and renal haemodynamic response to amino-acid administration in patients with IgA nephropathy

RATIONALE.: To establish relationship, if any, between renal morphologyand renal haemodynamic response to amino acids. DESIGN AND METHODS.: We investigated the correlation between renal haemodynamic regulationand morphology in a group of 15 patients with primary IgA nephropathy(IgAN) (age 26±2 years, BMI 24.4±1, GFR 64±5ml/min, RPF 377±34 mI/mm, FF 0.17±0.02). Twelvenormal subjects (age 30±3 years, BMI 24±1, GFR82±6 ml/min, RPF421±42 ml/min, FF 0.19±0.02)were studied as controls. IgA patients were divided into twogroups according to the histological staging of glomerular lesions:group I (n=7) stage II, and group II (n=8) stage III–IV. RESULTS.: In the basal state GFR was similar in the two groups and averaged64±9 and 64±6 ml/mm respectively. In contrast,FF was significantly lower in group II(0.14±0.01) (P<0.05)in comparison to group I (0.21±0.03) and controls (0.19±0.02).In order to evaluate the renal functional reserve, all studygroups underwent to an intravenous amino-acid infusion designedto increase plasma amino acid levels twofold (total from 2096±145to 4301±221 µmol/l in IgA nephropathy patientsand from 2272±83 to 3844±238 µmol/l in controls).In response to amino-acid infusion, GFR rose significantly ingroup I (GFR 20±2% and RPF 37±4% versus basal)and controls (GFR 20±2% and RPF 20±3% versus basal)(both P<0.01 vs basal). In contrast, in patients with moresevere glomerular lesions (group II) neither GFR nor RPF rosesignificantly (GFR –1±4% and RPF –8±6%versus basal) (P NS versus basal, P<0.01 versus group I andcontrols). CONCLUSIONS.: The data show that in IgA nephropathy: severe forms of glomerularlesions are associated with a complex alteration of glomerularhaemodynamic regulation, characterized by lower basal FF andloss of haemodynamic response to hyperaminoacidaemia.     

Immuno-histological analysis of dendritic cells in nasal biopsies of IgA nephropathy patients.

BACKGROUND: IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Intranasal vaccination of patients with IgAN has shown mucosal and systemic IgA hyporesponsiveness. Here, we investigated whether this IgA hyporesponse in IgAN patients can be explained by reduced numbers or altered subset distribution of dendritic cells (DCs) in nasal mucosa. METHODS: Eighteen IgAN patients and 18 healthy volunteers were recruited for this study. Nasal biopsies were taken, after local anaesthesia, from the lower edge of the inferior turbinate. Staining for different subsets of DCs was performed using specific monoclonal antibodies. To detect myeloid DCs, we used CD1a, DC-SIGN and blood dendritic cell antigen-1 (BDCA-1) as a marker and for plasmacytoid DCs we used BDCA-2. DC-cell numbers in the epithelium and in lamina propria were counted separately and expressed as positively stained cells per mm(2). RESULTS: Both myeloid and plasmacytoid DC could be demonstrated in nasal biopsies. Quantification showed that IgAN patients contained significantly more DC-SIGN-positive cells in the lamina propria compared to controls. In addition, in IgAN patients, we observed more CD1a-positive cells in the epithelium. No differences in BDCA-1 and BDCA-2-positive cells were found between patients and controls. The number of positively stained cells in the epithelial layer correlated strongly with the number of positively stained cells in the lamina propria. CONCLUSIONS: Patients with IgAN have higher numbers of CD1a-positive cells in the epithelial layer and more DC-SIGN-positive cells in the lamina propria. Therefore, the earlier observed IgA hyporesponsiveness in IgAN patients after mucosal vaccination cannot be explained by lower numbers of nasal DCs.     

The number of CD10-positive glomerular epithelial cells reflects renal prognosis in IgA nephropathy patients

BACKGROUND: The glomerular epithelial cells play an important role in glomerular filtration of the kidney. The disruption of these cells contributes to the development of glomerulosclerosis. The present study was performed to elucidate whether loss of the glomerular epithelial cells is associated with renal injury in patients with IgA nephropathy. PATIENTS AND METHODS: Thirty renal biopsy specimens from IgA nephropathy, 12 from minor glomerular abnormalities and 5 from normal controls were observed. The specimens from IgA nephropathy were divided into 2 groups: Group IgA-1, including 11 patients who had received a follow-up renal biopsy because of deterioration of renal function, and Group IgA-2, consisting of the remaining 19 patients without follow-up biopsy. Immunohistochemistry was performed using a monoclonal antibody against CD10 antigen that appears on mature epithelial cells of glomeruli. RESULTS: The average number of CD10-positive glomerular epithelial cells (GECs) was significantly lower in IgA nephropathy than in either minor glomerular abnormalities or the normal controls. In IgA nephropathy, there were significant correlations of the GECs with renal functions. The GECs were reduced along with the progression of histopathological damage. In group IgA-1, the GECs were significantly reduced at the second biopsy compared with the first biopsy, and significantly fewer in group IgA-1 than in group IgA-2 at the first biopsy. The GECs showed a significant correlation with renal prognosis during the follow-up period. CONCLUSIONS: The reduction of GECs was associated with renal dysfunction, histopathological damage and renal prognosis. The GECs may be a useful predictor of renal prognosis in IgA nephropathy.     

Effect of immunoglobulin depositions of glomerular sialic acids in patients with IgA nephropathy

A study of double immunofluorescence-staining of immunoglobulins and sialic acids in the glomeruli from patients with IgA nephropathy is described. Renal biopsy specimens from patients with IgA nephropathy were stained with rhodamine-labeled antihuman IgA, IgG or IgM antisera and then stained with FITC-labeled Limulus polyphemus (LPA), Tricum vulgaris (WGA) or antihuman C3 antisera. Marked positive stainings of IgA and C3 and positive binding of LPA or WGA were observed in the glomerular mesangial areas from patients with IgA nephropathy. LPA or WGA were not bound with glomerular capillary walls from patients with moderate and advanced stages of IgA nephropathy, although depositions of IgA and C3 were markedly observed in such walls. There was a significant inverse correlation between the deposition of IgA and the binding of LPA or WGA in glomerular capillary walls obtained from these patients with IgA nephropathy. The levels of proteinuria from patients with moderate and advanced stages of IgA nephropathy were significantly higher than those with minimal and slight stages of such disease. It is suggested that the decrease of sialic acids in glomerular capillary walls might be due to a deposition of IgA in some patients with IgA nephropathy. It is concluded that high levels of proteinuria might be due to the decrease of sialic acids in glomerular capillary walls from patients with moderate and advanced stages of IgA nephropathy.     

The glomerular response to IgA deposition in IgA nephropathy

Compelling evidence points to a role for IgA receptors in the pathogenesis of IgA nephropathy. The soluble form of the type I IgA receptor (FcalphaRI or CD89) forms complexes with IgA that can be found in patients' serum and that initiate the disease in CD89 transgenic mice. A nonclassic IgA receptor, identified as the transferrin receptor (TfR), is highly expressed in patients' mesangium and colocalizes with IgA deposits. TfR preferentially binds polymeric IgA1 complexes, but not monomeric IgA1 or IgA2. The TfR-IgA1 interaction is dependent on carbohydrate moieties because hypoglycosylated IgA1 has superior binding to TfR than normally glycosylated IgA1. Polymeric IgA1 binding enhances mesangial cell TfR expression and results in cell proliferation and inflammatory and profibrogenic cytokine and chemokine production, suggesting a pivotal role in mesangial cell proliferation, matrix expansion, and recruitment of inflammatory cells. We propose that, as a second event, activation of the classic, FcRgamma-associated transmembrane FcalphaRI expressed on circulating myeloid leukocytes takes place. FcalphaRI/gamma2 cross-linking in human FcalphaRI transgenic animals promotes disease progression by enhancing leukocyte chemotaxis and cytokine production, and IgA immune complexes from IgA nephropathy patients induce FcalphaRI-dependent cell activation. This review therefore details the functional consequences of IgA/receptor interactions and discusses proposed mechanisms to explain the development and chronicity of the disease.     

Macroscopic hematuria and proteinuria preceding renal IgA deposition in patients with IgA nephropathy

Although the clinical onset of IgA nephropathy is frequently impossible to define, macroscopic hematuria apparently heralds the onset of the disease in some patients. We describe the clinical course and renal histologic findings of four adults with IgA nephropathy who were diagnosed by the characteristic immunohistologic features in a second renal biopsy specimen. IgA was not detected in the initial renal biopsy specimens obtained 9 months to 4 years earlier. The first renal biopsy had been performed to evaluate macroscopic hematuria (recurrent in three patients), accompanied by pathologic proteinuria in two patients. Our observations suggest that the pathognomonic immunohistologic findings of IgA nephropathy may follow the clinical onset and raise questions about the presumed pathogenetic role of IgA in the early stages of this disease.     

Selective elevation of monomeric IgA1 in IgA nephropathy patients with normal renal function

The molecular form of the pathognomonic IgA in IgA nephropathy (IgAN) remains controversial. Because characterization of the molecular form of IgA molecules can lend insight into their origin (systemic v mucosal), we developed immunoassays to measure both total and J chain-containing (polymeric) IgA1 and IgA2. These assays were used to measure IgA in sera from two groups of IgAN patients (with normal or decreased renal function), as well as from a group of normal individuals. IgA1 levels were higher in both groups of patients with IgAN when compared with the controls. The elevation appeared to be restricted to non-J chain-containing (monomeric) IgA1 in patients with normal renal function, whereas polymeric IgA1 was also slightly elevated in patients whose renal function was diminished. While there were no significant differences between the groups in terms of the levels of total IgA2, the patient group with normal kidney function appeared to have lower levels of polymeric IgA2. The observation that the elevation in serum IgA appears to be restricted to the monomeric form of IgA1, at least when renal function is normal, implies a systemic origin of the pathognomonic IgA in IgAN and further suggests an abnormality in the regulation of IgA secretion by immunoglobulin-producing cells in bone marrow, the site of systemic IgA synthesis.     

肾功能不全的IgA肾病患者临床表现与病理特点分析

目的分析肾脏活体组织检查（简称：肾活检）时肾功能异常的IgA肾病患者的临床表现与病理特点。方法选择我院经肾活检确诊的190例IgA肾病患者为研究对象,以其患者血肌酐（SCr）130μmol／L为界分为2组：肾功能正常组（SCr〈130μmol／L）128例和肾功能异常组（SCr≥130μmol／L）62例。同时对其肾脏病理进行半定量评分,比较2组患者的临床病理特点,并且通过回归分析与其肾功损害相关的因素。结果与肾功能正常组相比,肾功能异常组男性比例明显增高（72．6％1;L28．9％,P〈0．01）,年龄更大[（34±10）岁比（30±9）岁,P〈0．01],病程更短[（11±17）]个月比（20±41）个月],同时收缩压更高[（141±19）比（123±17）mmHg,P〈0．01],24h尿蛋白定量增多[（3．31±2．70）g比（2．25±2．19）g,P〈0．01]。同时其患者肾脏病理反映慢性病变的指数均明显增高。多因素分析还显示,与肾活检时肾功能异常密切相关的危险因素包括男性,年龄增大,收缩压增高,24h尿蛋白定量增多,以及肾小管萎缩和间质纤维化指数增高。结论肾活检时肾功能异常的IgA。肾病患者临床表现和肾脏病理改变均明显加重,肾小管萎缩和间质纤维化指数增高与IgA肾病患者肾活检时肾功能异常独立相关。     

Minimum requirements for renal biopsy size for patients with IgA nephropathy.

In order to clarify the minimum requirements for renal biopsy size for a more accurate interpretation of renal biopsy information by light microscopy, we reanalyzed 92 open renal biopsy specimens in 92 patients with IgA nephropathy retrospectively. The mean number of functioning glomeruli per square millimeter in open renal biopsy specimens from 38 patients with a poor outcome was 1.2 +/- 0.4. In contrast, the mean number in 54 biopsy specimens from 54 patients with stable conditions for 10 years was 3.0 +/- 0.6. Therefore, there was a significant reduction (p less than 0.0001) in the numbers of functioning glomeruli in patients with a poor outcome. We found that the most important point in predicting the severity of tissue damage was detection not of the total numbers of glomeruli but of the density of glomeruli in given specimens in patients with IgA nephropathy. A biopsy sample of 1 mm x 7 mm in size of cortical origin is the minimum necessary to confidently interpret biopsy specimens from patients with IgA nephropathy.