observations in patients with a well-tolerated homotransplanted kidney: possibility of a new secondary disease

[Thrombotic microangiopathy/haemolytic uraemic syndrome. Histopathology update]

Thrombotic microangiopathy (TMA) encompasses different entities known as haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). The histopathological characteristics have remained constant since the initial description and consist in glomerular-type affectation with the presence of double contours, mesangiolysis and microthrombi. It is generally accepted that the vascular damage is related to the prognosis. Ultrastructure, together with conventional histology, shows notable changes in both capillaries and endothelial cells. A comprehensive histopathological study of the renal biopsy, using electronmicroscopy, is useful in the confirmation of a clinical suspicion and demonstrates the pathogenetic mechanisms in the microcirculatory damage. The close resemblance between the ultrastructural appearance and that seen with the light microscope of TMA and transplant glomerulopathy (TG) is precisely what suggests that both entities are subject to the same etiopathogenetic mechanism in which the endothelial cell is targeted. Recent advances in the pathology of atypical HUS, its relation with complement system and the discovery of specific therapeutic targets, has rekindled an interest in the study of TMA and the importance of renal biopsy.

Advances in the understanding of transplant glomerulopathy

Transplant glomerulopathy is a sign of chronic kidney allograft damage. It has poor survival and no effective therapies. This entity develops as a maladaptive repair/remodeling response to sustained endothelial injury and is characterized by duplication/multilamination of capillary basement membranes. This review provides up-to-date information for transplant glomerulopathy, including new insights into underlying causes and mechanisms, and highlights unmet needs in diagnostics. Transplant glomerulopathy is widely accepted as the principal manifestation of chronic antibody-mediated rejection, mostly with HLA antigen class II antibodies. However, recent data suggest that at least in some patients, there also is an association with hepatitis C virus infection, autoimmunity, and late thrombotic microangiopathy. Furthermore, intragraft molecular studies reveal nonresolving inflammation after sustained endothelial injury as a key mechanism and therapeutic target. Unfortunately, current international criteria rely heavily on light microscopy and miss patients at early stages, when they likely are treatable. Therefore, better tools, such as electron microscopy or molecular probes, are needed to detect patients when kidney injury is in an early active phase. Better understanding of causes and effector mechanisms coupled with early diagnosis can lead to the development of new therapeutics for transplant glomerulopathy and improved kidney outcomes.

Renal acute cellular rejection: correlation between the immunophenotype and cytokine expression of the inflammatory cells in acute glomerulitis, arterial intimitis, and tubulointerstitial nephritis

BACKGROUND

Acute renal transplant glomerulopathy (ARTG) refers to a glomerular inflammation mainly within the three 1st months posttransplantation, characterized by the influx of lymphomononuclear cells and swelling of endothelial and mesangial cells. The reported occurrence of ARTG is between 4.3% and 14% of all renal allografts. Investigations on the pathogenesis and on the impact on graft survival have been critically reviewed. The simultaneous occurrence of ARTG and acute vascular rejection (AVR) is common. However, cases of ARTG with no vascular inflammation suggest distinct pathogenic mechanisms for the entities. The objective of the present work was to compare the immunophenotype of the infiltrating cells and the cytokine immunoexpression (ICE) in ARTG with those of arterial intimal inflammation in AVR. We also compared the glomerular ICE with that in acute tubulointerstitial rejection and in arterial intimal inflammation.

METHODS

Forty kidney transplant biopsy specimens were allocated to 4 groups: 10 cases of acute tubular necrosis without ARTG or AVR (group I, Control); 10 cases of ARTG without AVR (group II); 10 cases of ARTG with AVR (group III); and 10 cases of AVR without ARTG (group IV).

RESULTS

The immunoexpressions of CD68 (macrophages), CD8 (cytotoxic T lymphocyte), CD4 (helper T lymphocyte), CD20 (B lymphocyte), S100 protein (antigen-presenting cells), interleukin (IL)-4, IL-10, and interferon (INF)-gamma-positive cells were evaluated in the glomeruli, arterial intima, and tubulointerstitium. In the comparative study between ARTG and arterial intimal inflammation, CD68+ cells predominated in the ARTG and T CD8+ cells in inflammation; the cytokine patterns were similar in both cases (IL-4 predominance).

CONCLUSIONS

Altogether, the data suggested similar pathogenic mechanisms, with mild sequential differences, for the glomerulitis, intimitis, and tubulointerstitial inflammation in cellular acute rejection. These findings seem to confirm the immunological nature of ARTG, indicating that ARTG might be included in the Banff classification as an additional parameter for acute rejection.

Longitudinal analysis of chronic allograft nephropathy: clinicopathologic correlations

BACKGROUND

Loss of the allograft from chronic allograft nephropathy and death of the patient from vascular, malignant, or infective disease are the major problems in renal transplantation today. Protocol biopsy of the long-term kidney has provided new data with which to develop strategies for prevention and treatment of chronic allograft nephropathy.

METHODS

Two series of long-term protocol biopsies are reviewed. In the first, renal biopsies were obtained at time 0, and at 3 months and 12 months, and the recipients of the renal allografts were followed up for up to 15 years. In the second, the kidneys of recipients of simultaneous pancreas kidney transplants were biopsied annually for 10 years, and the results correlated with clinical events.

RESULTS

Chronic allograft nephropathy is caused by acute and chronic immune-mediated damage, as well as by chronic calcineurin inhibitor nephrotoxicity. Both immune and nonimmune mechanisms exacerbate pre-existing donor disease and ischemia-reperfusion injury. Established interstitial fibrosis and arteriolar hyalinosis lead to progressive glomerular sclerosis and eventual loss of the graft.

CONCLUSION

Protocol biopsies have shown that clinical parameters of renal function underestimate the severity of chronic graft damage. Strategies for preventing or treating chronic renal allograft dysfunction and subsequent graft loss must better control rejection and simultaneously avoid nephrotoxicity.

The clinical impact of chronic transplant glomerulopathy in cyclosporine era

BACKGROUND

The clinical impact of chronic transplant glomerulopathy (CTG) on the outcome of kidney allograft receiving calcineurin inhibitors (CNIs) remains uncertain. A retrospective study of renal transplant recipients at Ospedale Maggiore of Milan was undertaken to evaluate the clinical outcome of patients with CTG.

METHODS

Among 666 biopsies taken at least 6 months after transplantation (Tx) in 498 transplant patients treated with CNIs, 28 cases (5.6%) of chronic transplant glomerulopathy (CTG) were identified and their clinical features at Tx, at follow-up and graft survival were compared with those of 56 controls transplanted in the same period and with kidney functioning 12 months after Tx. Clinical characteristics at biopsy and at 1 year after Tx were similar in the two groups.

RESULTS

After diagnosis graft function deteriorated in 22 patients (78.5%), while it remained stable in 6. Graft loss developed in 92 % of patients with proteinuria >2.5 g/day and in 33 % of those with lower proteinuria (P<0.005). In cases with more severe CTG the rate of graft loss was higher, though not significantly. Graft survival at 10 years was 48% in patients with CTG and 88% in controls (P<0.0001).

CONCLUSIONS

The incidence and clinical course of CTG do not seem to be modified by CNI-based immunosuppression. The evolution is unpredictable but the severity of glomerulopathy and proteinuria at follow-up are associated with progression to graft failure. Patients with CTG have a graft survival significantly worse than that of the general population of transplanted patients.

Antibody response against the glomerular basement membrane protein agrin in patients with transplant glomerulopathy

Chronic allograft nephropathy (CAN) of renal allografts is still the most important cause of graft loss. A subset of these patients have transplant glomerulopathy (TGP), characterized by glomerular basement membrane (GBM) duplications, but of unknown etiology. Recently, a role for the immune system in the pathogenesis of TGP has been suggested. In 11 of 16 patients with TGP and in 3 of 16 controls with CAN in the absence of TGP we demonstrate circulating antibodies reactive with GBM isolates. The presence of anti-GBM antibodies was associated with the number of rejection episodes prior to diagnosis of TGP. Sera from the TGP patients also reacted with highly purified GBM heparan sulphate proteoglycans (HSPG). Indirect immunofluorescence with patient IgG showed a GBM-like staining pattern and colocalization with the HSPGs perlecan and especially agrin. Using patient IgG, we affinity purified the antigen and identified it as agrin. Reactivity with agrin was found in 7 of 16 (44%) of patients with TGP and in 7 of 11 (64%) patients with anti-GBM reactivity. In conclusion, we have identified a humoral response against the GBM-HSPG agrin in patients with TGP, which may play a role in the pathogenesis of TGP.

Chronic allograft nephropathy: An update

Chronic allograft nephropathy is the most prevalent cause of renal transplant failure in the first post-transplant decade, but its pathogenesis has remained elusive. Clinically, it is characterized by a slow but variable loss of function, often in combination with proteinuria and hypertension. The histopathology is also not specific, but transplant glomerulopathy and multilayering of the peritubular capillaries are highly characteristic. Several risk factors have been identified, such as advanced donor age, delayed graft function, repeated acute rejection episodes, vascular rejection episodes, and rejections that occur late after transplantation. A common feature of chronic allograft nephropathy is that it develops in grafts that have undergone previous damage, although the mechanism(s) responsible for the progressive fibrosis and tissue remodeling has not yet been defined. Hypotheses to explain chronic allograft nephropathy include the immunolymphatic theory, the cytokine excess theory, the loss of supporting architecture theory, and the premature senescence theory. The most effective option to prevent chronic allograft nephropathy is to avoid graft injury from both immune and nonimmune mechanisms.

Immunolocalization of FGF-1 and receptors in glomerular lesions associated with chronic human renal allograft rejection

Glomerular lesions are considered one of the more detrimental pathologic changes associated with chronic rejection of renal allografts. To elucidate potential pathophysiologic mechanisms associated with transplant glomerulopathy, we examined the expression of acidic fibroblast growth factor (FGF-1) and its high-affinity receptors (FGFR) in both relevant renal transplant controls (n=5) and tissue from patients (n=19) who underwent nephrectomy following graft loss secondary to chronic rejection. In situ immunohistochemical analyses demonstrated minimal staining and distribution of FGFR and FGF-1, which was localized to the mesangial matrix in glomeruli from normal human kidneys. In situ hybridization failed to detect the presence of FGF-1 mRNA in control tissue. In contrast, each stage of the developing glomerular lesion associated with chronic rejection demonstrated the exaggerated appearance of FGF-1 protein in visceral and parietal epithelial cells. Intense staining for FGF-1 protein did not correlate with the increased appearance of FGF-1 mRNA, which was restricted to circulating inflammatory cells. Glomeruli in kidneys with findings of chronic rejection also exhibited increased immunodetection of both FGFR and PCNA in mesangial and epithelial cells. Immunogold labeling of chronically rejected visceral epithelial cells revealed both cytoplasmic and nuclear/localization of FGF-1, thereby establishing mitogenic potential of the growth factor. The enhanced appearance of both biologically active FGF-1 and FGFR suggests that this polypeptide may serve as an important mediator of growth responses associated with glomerular lesion development during chronic rejection.

Chronic renal transplant loss

Chronic rejection results from recurrent episodes of subclinical or clinically evident acute rejection, with or without involvement of chronic rejection-specific allogeneic immune mechanisms. The tissue damage occurs over a prolonged period of time, which allows the emergence of antigen-independent tissue repair mechanisms and intrarenal adaptations in response to progressive loss of renal mass (Fig. 1). The combination of these mechanisms leads, very likely, to the tissue remodeling of chronic rejection. The heterogeneous expression of chronic rejection may result from different types and specificities of allogeneic immune reactions as well as different contributions of antigen-independent factors that modulate the antigen-dependent tissue responses to injury. The extent to which these mechanisms participate in the overall picture is presently unknown as immunological parameters are not measured routinely in the follow-up of patients with chronic graft dysfunction. Furthermore, some grafts may undergo tissue remodeling as a consequence of predominantly antigen-independent mechanisms. Therefore, the term chronic allograft dysfunction may clinically be preferable over chronic rejection to describe the gradual decline in graft function months or years after transplantation in the absence of a well-defined mechanism or an accepted treatment.

Transplant glomerulopathy: evolution of morphologically distinct changes

The study was undertaken to redefine morphological appearance and clinical implications of the diagnosis of transplant glomerulopathy (TGP). Fifty-seven renal transplant biopsy specimens from thirty patients with the diagnosis of TGP were evaluated. Multiple repeat biopsies in several cases enabled us to follow the pattern of the evolution of the changes. Transplant dysfunction manifested itself 8 days to 13 years post-transplantation by proteinuria and/or elevated creatinine level. The earliest recognizable morphological change was the swelling of endothelial and mesangial cells. This stage was called evolving TGP. The intermediate stage was characterized by enlarged glomeruli with lobular simplification, spongy matrix, and glomerular basement membrane (GBM) deformities. The advanced stage of TGP showed pronounced GBM changes (reduplication, interposition). These light microscopic changes were associated with vascular rejection. Immunofluorescence showed significant glomerular deposition of IgM (83% of biopsies) and fibrinogen (66%). Electron microscopy at an early stage showed subendothelial widening with cellular debris and focal endothelial damage with fibrin deposition. In the advanced stage, complex GBM changes developed as a reparative response to the capillary wall injury. Effacement of foot processes was a constant finding at all stages. In follow-up, twenty-three allografts failed (77%), five patients are stable, and two died due to other causes. TGP has specific morphology with an attendant poor long-term prognosis for the allograft.

Renal allografts with glomerulonephritic change and proteinuria

Eight cases of renal allografts with glomerulonephritic change and proteinuria were classified into three groups according to the morphological features of the glomerular lesions. Group I (3 cases): By light microscope, remarkable reduplication of glomerular basement membrane (GBM), widening of mesangial region, and slight increase in mesangial cells, were observed. Electron microscopy revealed thickening of subendothelial space by deposition of electron-lucent material, mesangial interposition, and dense deposits in various regions (mainly in the subendothelial space). Group II (3 cases): By light microscope, crescent formation and reduplication of GBM were observed, while by electron microscope, changes of GBM similar to group I, but less remarkable, were seen. Group III (2 cases): Light microscope revealed spike formation in one case, but not in the other. With an electron microscope, subepithelial dense deposits were observed in both cases. Thickening of subendothelial space by deposition of electron-lucent material was noted in one case, while thickening of lamina densa was observed in the other case. Morphological change caused by rejection was observed in all eight cases, with six cases showing massive proteinuria and the other two showing slight proteinuria.

[Recurrence of the original disease in the transplanted kidney]

Recurrence of the original disease in the transplanted kidney is observed in 5.6%-9.3% of the patients. However, the clinical significance of recurrence is often minor. Diagnosis is easy in diseases with specific renal lesions, e.g., in dense deposit disease and IgA-nephropathy, but may be difficult if such a marker is missing. Recurrence is of special clinical importance in the following conditions: Membranoproliferative GN type I (in 33%, often severe) and type II (= dense deposit disease, recurrence in 90%, often minor), focal segmental glomerulosclerosis (in 48% of patients with a rapid course (less than 3 years) and in 12% of patients with a longer duration of the original disease; often severe), membranous nephropathy (recurrence rather rare, but often serious), and primary hyperoxaluria (in 100%). Mesangial IgA deposits recur in half of the patients with IgA-nephropathy and anaphylactoid purpura, but clinical findings are often minimal. Recurrence in anti-GBM-nephritis and SLE is rare. The study of recurrence may contribute to a better understanding of many renal diseases.

[Pathomorphology of transplant rejection and kidney biopsy diagnosis of the transplant]

Rejection processes concerning transplanted kidneys are traditionally classified as hyperacute, acute and chronic. It is, however, generally felt, that this time related classification is not satisfactorily in every respect. In order to come to a more differentiated histological diagnosis in the individual case, we resolved the time related classification categories and tried to specify rejection processes exclusively according to pathomorphological aspects. Thus 3 morphological rejection patterns or types can be differentiated: (1) a necrotizing-thrombotic rejection type (nth-rej), (2) a cellular rej (cell-rej) and (3) a sclerosing rej (scl-rej). These morphological rejection types match only partially with the time related categories. Especially it becomes apparent, that many cases have mixed rejection patterns. The pure as well as the mixed rejection patterns can exactly be defined in the histological diagnosis when the morphological categories are applied (e.g. severe cell-rej with moderate nth- and slight scl-component). This procedure is favourable in our opinion because a) the histological diagnosis now precisely informs the clinician about the whole spectrum of lesions present and b) individual cases can be compared with one another more effectively. In biopsy interpretation especially the following causes of functional deterioration have to be considered besides rejection processes: shock kidney, ureter stenosis, pyelonephritis, renal artery thrombosis and various types of glomerulonephritis (GN) in the transplant (de novo-GN, recurrent GN and others).

The improving utility of renal transplantation in the management of end-stage renal disease

The results achieved by treating patients with end-stage renal failure with allotransplantation have improved dramatically since the 1950s when immunosuppression was induced by total body irradiation and there was a lack of HLA typing. Although long-term hemodialysis offers prolonged survival and partial rehabilitation for many individuals with end-stage renal disease, the technique is inconvenient and time consuming. Patients are restricted by necessary proximity to the machine, dietary limitations, potential failure of access sites, and complications of various organ systems. Despite the availability of dialysis and the federal funds to partially pay for treatment, long-term dialysis still remains a costly process for the individual in need of care. During the same period when dialysis techniques improved and became widely available, transplantation of the human kidney became an established and justified treatment for some patients with end-stage renal disease. Those with successful kidney allografts may achieve remarkable recovery and are often able to return to normal lives. One of the more striking improvements in the results of renal transplantation in recent years had been the decline in morbidity and mortality. Mortality by the end of the first year after transplantation during which time most deaths occur, is currently less than 5 percent in a number of major medical units. In part, this decline represents a change in philosophy by transplant teams, who now tend to decrease immunosuppression and sacrifice the kidney rather than the patient in instances of inexorable rejection. In addition, declining mortality is directly attributable to improved methods of preventing, discovering, and treating patients with potential or real infections. More recently, in some centers, the rate of successful engraftment has shown gratifying improvement due to refinements in tissue typing, improved cross matching, new immunosuppressive therapies, and pretransplant conditioning with blood products. These recent improvements are the primary focus of this review. Unfortunately, until very recently, rates of functional survival of allografts have not been satisfactory.

Renal transplantation for patients with type I and type II membranoproliferative glomerulonephritis: serial complement and nephritic factor measurements and the problem of recurrence of disease

Fourteen patients with membranoproliferative glomerulonephritis as their original kidney disease received 16 renal allografts. All 14 patients are alive, 11 currently have functioning allografts, and one graft was lost to recurrence of membranoproliferative glomerulonephritis. Originally depressed serum complement (C3) concentrations returned to normal soon after transplantation in those patients with no clinical evidence of recurrence. Two patients with type II membranoproliferative glomerulonephritis had recurrence of disease. Nephritic factor (C3NeF) was high in both these patients before they received their transplants and was absent soon thereafter. However, abnormally high levels were again detected in their course. The one recurrence of type I membranoproliferative glomerulonephritis was associated with depressed C3, Clq, C4 and factor B but without C3NeF activity. Despite warnings of "high risks/ and "high mortality" associated with renal transplants in patients with membranoproliferative glomerulonephritis, we, because of these results and a review of the literature, continue to recommend renal transplants from both living related (LRD) and cadaver (CAD) donors in otherwise suitable patients who have renal failure due to membranoproliferative glomerulonephritis.

Recurrence of membranoproliferative glomerulonephritis following kidney transplantation. Serum complement component studies

Sixteen patients with membranoproliferative glomerulonephritis who required kidney transplantation because of renal failure were evaluated for evidence of recurrence of the original disease by serologic and morphologic studies. Of the 12 patients with transplant tissue available for study, seven showed membranoproliferative glomerulonephritis by light morphology. Four of these seven also had hypocomplementemia, and this hypocomplementemia was characterized by decreased serum CH50, C3 beta1A or C3-C9 but norma serum C1, C4 and C2 by hemolytic assay. Immunofluorescent microscopy demonstrated more intense glomerular deposition of C3 and properdin in the hypocomplementemic patients. Ultrastructural studies demonstrated intramembranous deposits typical of dense deposit disease in one patient who also had marked hypocomplementemia. One patient who had two transplant biopsies and persistent hypocomplementemia showed progression from predominantly mesangial glomerular changes to both capillary wall and mesangial abnormalities. This study has shown a high rate of recurrence of membranoproliferative glomerulonephritis in the transplanted kidneys. A high death rate was noted in persistently hypocomplementemic patients. The serum C profile in hypcomplementemic patients who received translants was similar to that seen before transplantation, but the signficance of this finding remains unknown.

Glomerular lesions after renal transplantation

Significant changes in glomeruli on light microscopy has been observed in 27 of 109 cadaveric renal allografts which functioned beyond 6 months. Tissue was available for study from all but two allografts. The histologic lesions were classified as follows: recurrent glomeruloneophritis, 9 cases (3 focal scierosis, 2 mesangial immunoglobulin A[IgA] disease, 2 mesangiocapillary glomerulonephritis, 1 dense deposit disease, 1 familial nephritis); de novo glomerulonephritis, 1 case (diffuse proliferative glomerulonephritis with crescents); and glomerular change of uncertain etiology, 17 cases (10 mesangiocapillary, 5 focal scierosis, 1 focal proliferative and 1 mesangial proliferative). These lesions were not distinguishable on light, fluorescent and electron microscopy from those in patients with spontaneous renal disease. All patients with glomerular lesions had proteinuria, and all but 3 had microscopic hematuria. Glomerular lesions were not significantly associated with early clinical rejection episodes or HLA compatibility. Presensitization of HLA antigens was significantly related to the occurence of a nonrecurrent glomerular lesion. Vescoureteral reflux was significantly more frequent in those with glomerular change (14 of 24) than in those without (13 of 48). Glomerular lesions were associated with a higher rate of graft loss due to renal transplant failure; renal function in survivors was significantly worse than in those without glomerular lesions.

Glomerulopathies in human renal allografts

The present study discusses the light, electron and immunofluorescence microscopy as well as some clinicopathologic correlations of rejection change in human renal allograft glomeruli. It is based on examination of 126 tissue specimens from 54 grafts obtained from 50 patients (1966-1973). The most frequent and characteristic lesion was membranous transplant glomerulopathy (MG) with irregular fibrillar thickening of capillary walls but without conspicuous hypercellularity. This thickening was caused by subendothelial depositsdifferent from classical fibrinoid lesions. During further progression, widening and peripheral extension of mesangium with degenerative changes became apparent. Advanced MG was encountered most frequently in the 2nd year after transplantation (TPL) at moderate to medium proteinuria and hypertension. It was accompanied by endarteristic rejection changes, and renal insufficiency set on usually in the course of the 3rd year. Nevertheless, the course, symptoms, and graft survival exhibited considerable variations. - The morphology and manifestations of destructive segmental transplant glomerulopathy (SG) depended on the time of its development. In the early stage (within about 3 months after TPL), the lesion was characterized by areas of fibrinoid insudation and necro(bio)sis associated with severe vascular changes, most frequently obliterative arterio(lo)pathy (OA). The ultrastructure was characterized by endothelial defects with host's polynuclear reaction and focal intravascular coagulation. The grafts thus affected failed soon, their function usually subsiding within the first trimester at a moderate, but gradually increasing proteinuria and severe persistent hypertension. The late from of destructive SG presenting as fibrohyaline obliteration of the loops with foam cells always accompanied advanced MG with severe arterial lesions. - Fluorescence microscopy revealed both linear and focal fixation of antisera, which, however had no apparent correlation with the microscopical and clinical presentations.