Tubular and interstitial expression of ICAM-1 as a marker of renal injury in IgA nephropathy

BACKGROUND: The upregulated renal expression of intercellular adhesion molecule 1 (ICAM-1) is associated with glomerular and interstitial infiltration of leukocytes. AIM: To test the hypothesis that renal expression of ICAM-1 may be predictive in the highly variable IgA nephropathy (IgAN). METHODS: ICAM-1 (CD54) in tubular epithelium and interstitial leukocytes, macrophages (CD14), and T cells (CD3) were assessed using avidin-biotin-peroxidase in renal biopsy specimens from 45 patients with IgAN and from 29 patients with no glomerulonephritis. RESULTS: In IgAN, tubular ICAM-1+ was seen in 25 of 45 (55%) biopsy specimens, associated with glomerular hypercellularity, glomerulosclerosis involving less than 50% of the glomerular area, interstitial cellular infiltration, tubular atrophy, and proteinuria (U = 44, p = 0.005). Interstitial ICAM-1+ leukocytes were correlated with glomerulosclerosis involving less and more than 50% of the glomerular area, tubular atrophy, interstitial fibrosis, and serum creatinine concentration (r = 0.6343, p < 0.001). In patients with an increase of 50% in the serum creatinine concentration, interstitial ICAM-1+ leukocytes and CD14+ and CD3+ cells were significantly more numerous than in patients with a stable creatinine concentration. In patients with no glomerulonephritis, tubular ICAM-1+ was seen in 7 of 29 (24%) biopsy specimens, inversely correlated with the number of normal glomeruli and associated with glomerulosclerosis covering more than 50% of the glomerular area, tubular atrophy, and creatinine. CONCLUSIONS: Tubular and interstitial expression of ICAM-1 can be a marker of tubulointerstitial disturbance in IgAN. Interstitial ICAM-1 may be an adverse predictor of disease progression.     

Asymptomatic low molecular weight proteinuria: a report on 5 cases

In children with asymptomatic proteinuria, a high proportion of low molecular weight (LMW) proteins is an indicator of tubular malfunction. In a routine screening program covering the last 15 years and involving 280,000 children, aged between 3 and 19 years, we have identified 5 boys with LMW proteinuria. In 4 of these, renal biopsy was histologically normal on the first presentation. Follow-up for 4-16 years showed normal growth curves, but further evidence of tubular dysfunction appeared: glycosuria and hypophosphatemia in 2 patients; one of them had also aminoaciduria and rising serum creatinine (greater than 1.2 mg/100 ml). Another patient had only increased serum creatinine. The other two, still less than 13 years old, show so far no other abnormality than persistent LMW proteinuria. It is suggested that early identification of LMW proteinuria may presage gradual development of progressive tubular dysfunction with age and that such patients should be followed up indefinitely.     

The morphological compensatory change of peritubular capillary network in chronic allograft rejection

Abstract:  To clarify the compensatory hemodynamic alterations in the interstitium of renal allograft biopsies with chronic rejection, we evaluated the morphological changes in the peritubular capillary (PTC) network. Seven renal biopsy specimens from recipients with chronic rejection presenting with elevation of serum creatinine of 1.9 ± 0.5 mg/dL were examined. Renal biopsy specimens from their counterpart donors were used as normal controls. In each specimen, non-pathological interstitial areas without fibrosis, tubular atrophy or cell infiltration were compared with pathological areas (PA) showing fibrosis and/or tubular atrophy using a computer image analysis. Morphological measurements revealed that the mean cut surface area of the PTC in the non-pathological and pathological interstitial areas in the recipient biopsies were significantly larger than that of the normal controls (p < 0.001 and 0.001, respectively). In the recipient biopsies, both of the mean cut surface areas of the tubules and PTC in the non-pathological areas were significantly higher than those in the PA (p < 0.001). The mean glomerular diameter in the recipient biopsies was also significantly higher than that of the donors (p < 0.01). In this study, we provided pathological evidence for the compensatory interstitial and glomerular hemodynamic alterations in kidney graft with chronic rejection and the condition as single kidney.     

Morphologic evaluation and integrin expression profile of renal tubular cells cultured from percutaneous renal biopsy specimen

Kidney biopsy is an indispensible procedure for making a pathologic diagnosis of renal diseases by fixing and staining the biopsy specimen. However, it is not a routine procedure to culture the cells from a renal biopsy specimen directly, or to utilize the cultured cells for any kind of diagnostic or functional evaluation. In this study, primary culture of the renal tubular epithelial cells was tried from a piece of percutaneous kidney biopsy specimen. Successive passages of the cells were possible until fourth passage. With these cells, morphologic characteristics of the cultured cells and integrin expression profiles were investigated. On light and electron microscopy, these cells were characterized by the cobblestone-like growth, presence of microvilli and tight junction, and the preservation of polarity. Immunohistochemical studies demonstrated the epithelial nature of these cells and particularly their differentiation from renal tubular epithelial cells, of either proximal or distal nephronic segment. The integrin profile confirms the epithelial nature of the cell. We hope that our results facilitate the understanding of pathophysiology of renal tubular cells from the patient directly.     

Interaction of acidic fibroblast growth factor and transforming growth factor-beta in normal and transformed glia in vitro.

The mitogenic and morphological effects of acidic fibroblast growth factor (aFGF) and transforming growth factor-beta (TGF-beta) were assessed on cultured fetal rat astrocytes and C6 rat glioma cells in the presence and absence of serum. Astrocytes incubated with aFGF exhibited an increase in mitotic activity and characteristic morphological changes involving extensive process formation and rounding of cell bodies. Astrocytes incubated with TGF-beta underwent a slight decrease in mitotic activity and remained morphologically unchanged. Cells exposed to a combination of aFGF and TGF-beta demonstrated an attenuation of both the mitogenic and morphological changes observed in the presence of aFGF alone. The C6 glioma cells cultured in the presence of aFGF underwent a characteristic morphological change from a rounded piling cell mass to a more spindle-shaped bipolar cell layer, accompanied by an increase in mitotic activity. In contrast to the astrocyte cultures, increased growth and similar morphological effects were produced by TGF-beta. The combination of aFGF and TGF-beta did not result in attenuation of the mitogenic and morphological changes (as seen in astrocytic cells). These results suggest that, in normal fetal rat astrocytes, TGF-beta is capable of attenuating the mitogenic and morphological changes induced by aFGF in vitro. In the transformed C6 glioma cell line, aFGF and TGF-beta elicit similar mitogenic and morphological changes, without evidence of an antagonistic interaction as seen in normal astrocytes.     

Analysis of histological findings of testicular biopsies in male infertility

Histological findings of testicular biopsy were studied following the Johnsen's score count method in 68 cases of idiopathic male infertility, and the relation between serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), and testosterone (T) and histological findings were analyzed in the same cases. In oligozoospermia, there were no cases showing a Johnsen's score lower than 4. The score counts ranged widely from 1 to 9 in azoospermia. The cases with the Johnsen's score count lower than 4 revealed high values of serum LH and FSH and a low level of serum T. There was no relationship between Leydig cell accumulations or thickness of the seminiferous tubular walls and score values. Further examination using ABC (avidin biotin complex) method was carried out to find the localization of FSH and T in the testicular tissues. Immunohistochemical localization FSH was not noted in normal testicular tissues obtained the autopsy cases and testicular biopsy specimens of idiopathic male infertility. The localization of T was found in the Leydig cells and the Sertoli cells of normal and infertile testes. In the cases with the thickness of tubular walls, Sertoli cells were not stained. This fact might indicate that absence of T in Sertoli cells is related to spermatogenetic maturation only with the thickness of seminiferous tubular walls.     

Absence of H(+)-ATPase in cortical collecting tubules of a patient with Sjogren's syndrome and distal renal tubular acidosis.

Distal urinary acidification abnormalities may arise from transepithelial voltage defects, permeability defects, or proton-secretory defects, but tests to determine the cellular mechanisms underlying secretory abnormalities have not previously been reported. A patient with Sjogren's syndrome and distal renal tubular acidosis due to a secretory defect is described, whose kidney biopsy was examined by fluorescent immunocytochemistry with an antibody to the M(r) 31,000 subunit of the mammalian kidney vacuolar H(+)-ATPase and was compared with normal human kidney. Staining with the anti-H(+)-ATPase antibody in normal human kidney was detected in the brush border microvilli and subvillar invaginations of the proximal tubule and in intercalated cells in the collecting duct. A biopsy sample from the patient was devoid of any anti-H+-ATPase staining in the intercalated cells. Staining was also absent from the proximal tubule brush border microvilli but was present in the subvillar invaginations. Although autoantibodies to normal human kidney membrane proteins were detected in the serum by immunoblot analysis, no immunocytochemical evidence for anti-intercalated cell autoantibodies was observed in the patient's serum. This report demonstrates that the basis for the proton secretory defect in some patients with distal renal tubular acidosis is likely the absence of H(+)-ATPase in the intercalated cells. It also illustrates the potential diagnostic utility of anti-H(+)-ATPase antibodies in the classification of distal renal tubular acidoses.     

Tubular proteinuria in IgA glomerulonephritis

In the renal biopsy samples of some patients with IgA glomerulonephritis (IgA GN), tubulointerstitial changes and a significant correlation between these changes and the serum creatinine levels had been observed earlier. In order to get an insight into the function of the tubules, 45 patients with IgA GN have been examined for proteinuria with special reference to low molecular weight (LMW) proteins, also called tubular proteins using sodium-dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE). Thirty-seven of the 45 patients had proteinuria (200-1890 mg/day). On the basis of the middle molecular weight/high molecular weight (MMW/HMW) protein ratio, the proteinuria was non-selective in 28. Twenty-nine patients had 40-200 mg LMW protein/day in the urine. There was a statistically significant correlation between the tubulointerstitial changes seen in the renal biopsy samples (characterized by the tubulointerstitial index) and the tubular proteinuria. On the basis of these results it is suggested that in most patients with IgA GN there is, in addition to the glomerular lesion, also morphological and functional tubulointerstitial damage, which is in connection with the progression of the disease.     

改良的大鼠近端肾小管上皮细胞分离纯化方法

目的　建立纯度高、操作简便的大鼠近端肾小管上皮细胞分离纯化方法。 方法 Wistar大鼠无菌取肾前先心脏抽血替代原位肾脏灌注，分离肾皮质，经Ⅰ型胶原酶消化后用45% Percoll分离液制备细胞悬液直接连续密度梯度离心。所得细胞用含10%胎牛血清的DMEM-F12培养基原代培养并传代，根据细胞形态、细胞角蛋白18（CK18）和水通道蛋白1（AQP1）免疫细胞化学染色及碱性磷酸酶化学染色进行鉴定。 结果 此简化方法获得的肾小管细胞中肾小球掺杂明显减少，培养4～5 d后细胞融合长满，呈典型上皮样细胞的鹅卵石状，其CK18、AQP1免疫细胞化学染色及碱性磷酸酶化学染色几乎均呈阳性，证实所培养细胞为近端肾小管上皮细胞。 结论 改良后的分离纯化方法可获得大量高纯度近端肾小管上皮细胞，操作简便。     

Clinical value of "zero-hour" biopsy in kidney transplantation

We have performed 115 "zero-hour" biopsies of transplanted kidneys since 1994. Donor kidneys were divided into five groups, based on the morphological findings of "zero-hour" biopsies. No morphological abnormalities were found in 38.26% of the cases (group 1). Arteriolosclerosis was present in 22.61% of donor kidneys (group 2). Specific morphological alterations, i.e. acute tubular necrosis (24.35%), tubulointerstitial nephritis (5.22%) or glomerulonephritis (9.56%) were detectable in the remaining cases (groups 3-5). During an average of 644 days after transplantation clinical and histological follow-up were performed. According to our observations: 1. Higher creatinine was found in patients with grafts with arteriolosclerosis (group 2). 2. There were more non-viable grafts and longer periods of delayed graft function in patients with acute tubular necrosis (group 3). 3. Higher serum creatinine, more frequent rejections with the need of secondary hemodialysis were observed in patients who received a kidney with "zero-hour" biopsy of tubulointerstitial nephritis (group 4). 4. The only complication observed in patients with glomerulonephritis donor kidneys was delayed functioning of the graft (group 5). Biopsies did not cause complication in any of our patients. In conclusion, "zero-hour" biopsies can be useful and safe tools to predict early graft function. Besides, "zero-hour" biopsies help histological interpretation of consecutive graft re-biopsies.     

Renal proximal tubular metabolism of protein-linked pentosidine,an advanced glycation end product

BACKGROUND: Pentosidine, an advanced glycation end product, accumulates in plasma proteins of uremic patients. Its fate is, however, yet to be fully understood. METHODS: Three cell lines, JTC-12 (proximal tubular cells), MDCK (distal tubular cells), and BALB3T3 (nonrenal cells), were cultured in a double chamber system and were exposed to uremic serum, and the contents of protein-linked pentosidine derived from uremic sera were determined in each medium by HPLC assay. The presence of pentosidine in the cytoplasm of these cells was assessed by immunoperoxidase staining. RESULTS: When the apical cell membrane was exposed to uremic serum (fortified in the upper chamber), the contents of protein-linked pentosidine in the upper medium decreased by up to 30% after 24- and 48-hour incubations of JTC-12 cells but not of other cells. On the other hand, the contents of protein-linked pentosidine in the lower medium did not change. By contrast, exposure of the basolateral cell membrane of the three cell lines to uremic serum (fortified in the lower chamber) did not change the contents of protein-linked pentosidine both in the upper and lower medium after a 24-hour incubation. Pentosidine was detected immunohistochemically in the cytoplasm of JTC-12 cells, but not of BALB3T3 and MDCK cells, the apical membranes of which were exposed to uremic sera for 8 h. The immunoreaction disappeared 48 h after exposure. Pentosidine was not detected in the cytoplasm of JTC-12 cells, the basolateral membranes of which were exposed to uremic sera. The relevance of the in vitro results to humans was demonstrated by immunohistochemical studies in normal human kidney tissues showing that pentosidine was identified in the proximal renal tubules. CONCLUSION: These results suggest that the proximal tubular cells play a role in the disposal of plasma pentosidine.     

Modulators of growth in primary culture of rat proximal tubular cells

Summary: The effects of known growth factors and circulating serum factors in animals following unilateral nephrectomy on cellular hypertrophy and hyperplasia were studied in primary culture of rat proximal tubular cells. the cultured cells were derived from normal rat kidney, as well as from rat kidneys which had undergone compensatory renal hypertrophy. Cellular thymidine incorporation was stimulated with insulin-like growth factor 1 (IGF-1; P <0.001), epidermal growth factor (EGF; P <0.01) and additively by the combination of IGF-1+EGF ( P <0.0001). Transforming growth factor β₁ (TGF β₁) potently inhibited thymidine incorporation in the presence or absence of these growth factors. Cellular protein content was increased in the presence of IGF-1 ( P <0.01). the addition of 10% serum harvested from sham operated (Sx) animals to cell cultures derived from Sx animals significantly increased cell protein content ( P <0.02), and stimulated cellular thymidine incorporation ( P <0.005). the addition of 10% serum harvested from unilaterally nephrectomized (Nx) animals further enhanced the growth response. In cell cultures derived from Nx rats, a further marked stimulation of thymidine incorporation and cellular protein was observed in the presence of both Sx and Nx serum, indicating an increased sensitivity of these cells to serum-derived factors. In summary, the growth factors tested have direct effects in regulating rat renal tubular cell growth. Circulating factors stimulating proximal tubular cell growth are present in animals which have undergone nephrectomy. Renal tubular cells derived from animals with compensatory renal hypertrophy are sensitized to the effects of the manipulations which enhance proximal tubular cell growth.     

p62/SQSTM1 prominently accumulates in renal proximal tubules in nephropathic cystinosis

Background

Nephropathic cystinosis, a lysosomal storage disorder, is associated with generalized proximal tubular dysfunction and progressive renal failure. The underlying molecular and cellular mechanisms leading to renal tubular injury remain largely unknown. Abnormal induction of autophagy has been shown in cystinosis. We have studied the autophagic flux in cystinosis by evaluating autophagy-specific substrates.

Methods

LC3 and p62 expression was evaluated by (1) immunohistochemistry performed on kidney biopsies obtained from four nephropathic cystinosis patients, four patients with renal injury due to causes other than cystinosis, and four normal kidney tissues and (2) fluorescence imaging in cultured renal proximal tubular epithelial (RPTE) cells obtained from four nephropathic cystinosis patients and two lots of normal primary RPTE cells, both in basal and starvation conditions. p62 expression was also corroborated by western blot analysis in RPTE cells.

Results

There was a significant buildup of p62 protein in patients with nephropathic cystinosis, specifically in the proximal tubules in kidney biopsies and RPTE cells (p?=?0.0004), and the accumulation was further enhanced upon starvation. Cystinotic RPTE cells exhibited a significant co-localization of p62 with LC3.

Conclusions

Our findings indicate a potential block in the autophagic flux in cystinosis, thus providing key insights into the underlying mechanisms of tubular injury in cystinosis.     

Biologically active ADAMTS13 is expressed in renal tubular epithelial cells

ADAMTS13 mRNA, which encodes the von Willebrand factor-cleaving protease, has been detected in a variety of tissues, including the kidney. The aim of our study was to characterize tubular expression and bioactivity of ADAMTS13. ADAMTS13 mRNA was detected in cultured primary human renal tubular epithelial cells (HRTEC) and in A498 cells, a human renal carcinoma cell line, by real-time PCR. Protein was detected using immunofluorescence and immunoblotting. Immunoblots demonstrated that the protein was secreted. The protease was proteolytically active in both cell lysates and cleaved the FRETS–VWF73 substrate. ADAMTS13 was demonstrated in situ in the renal cortex by immunohistochemistry. Protease was detected in both the proximal and distal renal tubules in normal renal tissue (n = 3) as well as in patients with tubular disorders (n = 3). Immunoblotting revealed that ADAMTS13 was present in the urine of patients with tubulopathy (n = 5) but not in normal urine. ADAMTS13 in urine had a molecular size similar to that in plasma, which indicates that the protease originates in the tubuli because such large proteins do not normally pass the glomerular filter. In conclusion, human renal tubular epithelial cells synthesize biologically active ADAMTS13 which may, after release from tubuli, regulate hemostasis in the local microenvironment.     

间隙连接蛋白43表达改变对肾小管上皮细胞转分化的影响

目的 研究肾小管上皮细胞-肌成纤维细胞转分化（TEMT）过程中间隙连接蛋白43（connexin 43）表达和细胞间通讯功能的变化,以及上调connexin 43水平对TEMT的影响。方法 用转化生长因子（TGF）β1刺激人肾小管上皮细胞系（HKC）,检测connexin 43、上皮细胞标志物E-钙黏蛋白（E-cadherin）和肌成纤维细胞标志物α-SMA、vimentin的表达。用激光共聚焦显微镜荧光漂白恢复（FRAP）技术检测HKC细胞间通讯功能。通过pLNCX2- connexin 43病毒质粒转染HKC上调connexin 43的表达,检测以上各指标的变化,观察对TEMT的影响。结果 HKC经TGF-β1刺激后．其α-SMA和vimentin mRNA和蛋白质表达增强,而E-cadherin和connexin 43表达下降（P＜0．05）,细胞间通讯功能降低（P＜0．05）。connexin 43高表达后,TEMT程度明显减轻。结论 上调肾小管上皮细胞间通讯功能可部分减轻TEMT程度。     

Inhibition of Intracellular Clusterin Attenuates Cell Death in Nephropathic Cystinosis

Nephropathic cystinosis, characterized by accumulation of cystine in the lysosomes, is caused by mutations in CTNS. The molecular and cellular mechanisms underlying proximal tubular dysfunction and progressive renal failure in nephropathic cystinosis are largely unclear, and increasing evidence supports the notion that cystine accumulation alone is not responsible for the end organ injury in cystinosis. We previously identified clusterin as potentially involved in nephropathic cystinosis. Here, we studied the expression of clusterin in renal proximal tubular epithelial cells obtained from patients with nephropathic cystinosis. The cytoprotective secretory form of clusterin, as evaluated by Western blot analysis, was low or absent in cystinosis cells compared with normal primary cells. Confocal microscopy revealed elevated levels of intracellular clusterin in cystinosis cells. Clusterin in cystinosis cells localized to the nucleus and cytoplasm and showed a filamentous and punctate aggresome-like pattern compared with diffuse cytoplasmic staining in normal cells. In kidney biopsy samples from patients with nephropathic cystinosis, clusterin protein expression was mainly limited to the proximal tubular cells. Furthermore, expression of clusterin overlapped with the expression of apoptotic proteins (apoptosis-inducing factor and cleaved caspase-3) and autophagy proteins (LC3 II and p62). Silencing of the clusterin gene resulted in a significant increase in cell viability and attenuation of apoptosis in cystinosis cells. Results of this study identify clusterin as a pivotal factor in the cell injury mechanism of nephropathic cystinosis and provide evidence linking cellular stress and injury to Fanconi syndrome and progressive renal injury in nephropathic cystinosis.     

Silicon nephropathy: a possible occupational hazard

A 37-year-old white male, working in a tile factory, presented proteinuria with no obvious tubular dysfunctional. Renal biopsy disclosed a mild focal segmental proliferative glomerulonephritis. Distinct alterations were found by electron microscopy, especially in the proximal tubular cells. Because of a history of heavy dust exposure the silicon content was determined in the kidney biopsy tissue. The finding of 150 mg/kg silicon on tissue dry weight supports the diagnosis of silicon nephropathy.     

FK506-induced kidney tubular cell injury.

Some renal changes associated with cyclosporine, such as tubular vacuolization and glomerular thrombosis, have also been reported with FK506. Furthermore, FK506 therapy is associated with a decrease in glomerular filtration rate and renal plasma flow and an increase in renal vascular resistance. We studied the in vitro tubular cell sensitivity to FK506 in comparison with CsA, the ultrastructural changes induced by FK506 and CsA, and the effect of both drugs on tubular cell growth in vitro. We also investigated whether FK506 and CsA induced endothelin-1 (ET-1) secretion of cultured tubular cells and whether this stimulatory effect coincided with a change in the endothelin systemic synthesis. Exposure of tubular cells to high concentrations of FK506 or CsA (10, 50, 100 microM) induced a time- and dose-dependent cell injury in vitro. The damage induced by FK506 and CsA was characterized by a direct cytotoxic effect on tubular cells, as expressed by release of 3H thymidine from prelabeled cells, N-acetyl-beta-D-glucosaminidase release, and cell detachment. Ultrastructural changes (vacuolizations, swelling, and mitochondrial enlargement) and inhibition of the growth of cultured tubular cells were also observed at high concentrations of FK506 and CsA. Low concentrations of FK506 and CsA (1, 0.1, 0.01, 0.001 microM) were not cytotoxic and induced only a minimal inhibitory effect on the growth of tubular cells in vitro. We demonstrated that FK506 (1, 0.1, 0.01 microM) time-dependently stimulated the secretion of endothelin by cultured tubular cells. CsA 10, 1, 0.1, 0.01 also exerted an enhancing effect on ET-1 secretion in cultured tubular cells. We observed that the concentration of CsA that induced the most important enhancing effect was 10 or 100 times higher than that required for FK506 to observe the same effect. The concentrations of FK506 or CsA that induced ET-1 secretion were not cytolytic for tubular cells in vitro. FK506- or CsA-treated rats showed an increase in serum level of ET-1 in comparison with the control. Through the stimulatory effect on endothelin secretion by tubular cells, FK506 and CsA may induce a perturbation of renal hemodynamics. Concentrations of FK506 and CsA, higher than established serum levels but close to those reached in tissues, are cytotoxic for tubular cells and induced ultrastructural changes and a significant delayed regeneration.     

Severe crescentic BK virus nephropathy with favourable outcome in a transplanted patient treated with Leflunomide

Herein reported is a severe case of BK virus nephropathy, probably caused by an intense/overimmunosuppression and identified 17 months after transplantation. The diagnostic biopsy showed extracapillary proliferation and typical cytopathic lesions, both in tubular epithelial cells and in those of the glomerular crescents. Severe inflammatory infiltrates, tubulitis, tubular atrophy and fibrosis were also observed. Immunohistochemistry and molecular biology disclosed the presence of an AS variant of the BK virus with a high viral load, both in renal tissue and urine. Immunosuppression was reduced and Leflunomide therapy administered for a month. Although this led to an improvement in the renal function, the therapy had to be suspended due to the onset of a skin rash. A second biopsy was performed 7 months later. The cellular crescents were no longer present and there was no evidence of either histologic or immunohistochemical findings consistent with an active BK virus infection. Tubular atrophy and interstitial fibrosis were still present. In addition, fibrotic crescents, which may be interpreted as late scarring changes of previous epithelial proliferation, were found. Although molecular investigation still showed the presence of the BK virus, the viral load in renal tissue, urine and serum was greatly reduced. Indeed, serum and urine viral load was still low at the last control, five months after the second biopsy. The morphologic and clinical evolution are reported and the possible role of the therapy is discussed.