Capillary C4d deposition as a marker of humoral immunity in renal allograft rejection

Mesangial C4d deposition at diagnosis in childhood immunoglobulin A nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is a major cause of end-stage renal disease. Complement activation via the lectin pathway influences outcomes in IgAN. We examined the association of glomerular C4d deposition with clinicopathological severity at diagnosis and the disappearance of proteinuria in Japanese pediatric IgAN patients.

METHODS

We retrospectively analyzed 25 children newly diagnosed with IgAN at Hokkaido University Hospital. We evaluated glomerular C4d immunofluorescent staining at diagnosis. We compared clinical findings, pathological findings (based on Oxford classification), and the disappearance of proteinuria within 24 months after renal biopsy between C4d-positive and C4d-negative patients.

RESULTS

Glomerular C4d staining was observed in 14 patients (56.0%). C4d-positive patients had significantly higher proteinuria at diagnosis than C4d-negative patients (2.03 g/gCr vs 0.78 g/gCr; P = 0.005). The number of glomeruli with segmental glomerulosclerosis or adhesion (8.0% vs 0.0%; P = 0.046) and the extent of tubular atrophy/interstitial fibrosis (9.46% vs 2.86%; P = 0.031) were significantly increased in C4d-positive patients compared with C4d-negative patients. Further, the proportion of patients with modified T1 (>10%) was significantly higher in the C4d-positive group than the C4d-negative group. There was no significant difference, however, in the disappearance rate of proteinuria at 24 months after renal biopsy between groups (64% vs 82%; P = 0.149).

CONCLUSIONS

Glomerular C4d deposition was associated with clinicopathological severity at diagnosis in Japanese pediatric patients with IgAN. Glomerular C4d deposition, however, was not a predictor of the disappearance of proteinuria within 24 months after diagnosis in Japanese pediatric patients with IgAN.

Serum miR-338-5p, soluble B-cell-activating factor, allo-antibodies, and renal transplantation

BACKGROUND

The objective of the study was to explore the expression features of serum miR-338-5p and soluble B-cell-activating factor (sBAFF) in renal transplant recipients.

METHODS

Follow-up renal transplant recipients (n = 49) were enrolled in this study (male/female: 38/11). Healthy volunteers were controlled; 2 mL of peripheral blood from each subject was collected. Total RNA was extracted from serum by use of the miRNeasy Serum/Plasma Kit (QIAGEN), and miR-338-5p was amplified by means of quantitative real-time reverse transcriptase-polymerase chain reaction. sBAFF was detected by means of enzyme-linked immunoassay. LABScreen Mix (LSM12) (One Lambda) was used to test the level of anti-human leukocyte antigen (HLA) I antibody (Ab), anti-HLA II Ab, and anti-major histocompatibility complex class I chain-related A (MICA) Ab. All data are shown as mean ± SD and were analyzed by use of SPSS software 17.0.

RESULTS

Compared with healthy volunteers, serum miR-338-5p in recipients was statistically downregulated (2.79 ± 2.5 versus 0.09 ± 0.12, P < .001); sBAFF in recipients was significantly upregulated (1321 ± 950 pg/mL versus 534 ± 327 pg/mL, P < .01); serum anti-HLAII Ab, anti-MICA Ab, and anti-HLA+MICA Abs all statistically increased in recipients (P < .05). Spearman correlation analysis showed that miR-338-5p was significantly negatively correlated with sBAFF (r = -0.51, P < .001) and anti-HLA II antibody with mean fluorescence intensity value >1000 (r = -0.322, P < .05). Analysis results also suggested that sBAFF was significantly negatively correlated with anti-MICA Ab, with mean fluorescence intensity value >1000 (r = -0.579, P < .05).

CONCLUSIONS

miR-338-5p is closely correlated with the procedure of renal allograft antibody-mediated rejection.

[Current aspects of acute humoral rejection]

Acute clinical antibody-mediated rejection is currently defined by (1), an acute renal failure occurring during the first months following transplantation, (2), at least a microcirculation inflammation (glomerulitis and peritubular capillaritis) on kidney biopsy and (3), the presence in peripheral blood of donor specific antibodies, mostly anti-human leukocyte antigen (HLA) antibodies. The prognosis of this rejection is scored using the severity of vascular lesions and the positivity of C4d on peritubular capillaries. Recently, a subclinical variety of antibody-mediated rejection was recognized as an entity because, as the clinical rejection, it leads to chronic antibody-mediated rejection, currently the most frequent cause of graft loss. The description of these various aspects of antibody-mediated rejection allowed a better understanding of its pathophyiology that may lead in a near future to a more specific treatment.

Cell distance mapping identifies functional T follicular helper cells in inflamed human renal tissue

T follicular helper (TFH) cells are critical for B cell activation in germinal centers and are often observed in human inflamed tissue. However, it is difficult to know if they contribute in situ to inflammation. Expressed markers define TFH subsets associated with distinct functions in vitro. However, such markers may not reflect in situ function. The delivery of T cell help to B cells requires direct cognate recognition. We hypothesized that by visualizing and quantifying such interactions, we could directly assess TFH cell competency in situ. Therefore, we developed computational tools to quantify spatial relationships between different cell subtypes in tissue [cell distance mapping (CDM)]. Analysis of inflamed human tissues indicated that measurement of internuclear distances between TFH and B cells could be used to discriminate between apparent cognate and noncognate interactions. Furthermore, only cognate-competent TFH cell populations expressed high levels of Bcl-6 and interleukin-21. These data suggest that CDM can be used to identify adaptive immune cell networks driving in situ inflammation. Such knowledge should help identify diseases, and disease subsets, that may benefit from therapeutic targeting of specific T cell-antigen-presenting cell interactions.

Association of C4d deposition with clinical outcomes in IgA nephropathy

BACKGROUND AND OBJECTIVES

Several studies have suggested that activation of the complement system is a contributing pathogenic mechanism in IgA nephropathy (IgAN). C4d staining is an inexpensive and easy-to-perform method for the analysis of renal biopsies. This study aimed to assess the clinical and prognostic implications of C4d staining in IgAN.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This retrospective cohort study included 283 patients with IgAN in 11 hospitals in Spain who underwent a renal biopsy between 1979 and 2010. The primary predictor was mesangial C4d staining. Secondary predictors included demographic, clinical, and laboratory characteristics, and Oxford pathologic classification criteria. The primary end point was the cumulative percentage of patients who developed ESRD, defined as onset of chronic dialysis or renal transplantation. C4d was analyzed by immunohistochemical staining using a polyclonal antibody. Kaplan-Meier and Cox proportional hazards analyses were performed to evaluate the effect of C4d staining on renal survival.

RESULTS

There were 109 patients (38.5%) and 174 patients (61.5%) who were classified as C4d positive and C4d negative, respectively. Renal survival at 20 years was 28% in C4d-positive patients versus 85% in C4d-negative patients (P<0.001). Independent risk factors associated with ESRD were as follows: proteinuria (hazard ratio [HR] per every 1 g/d increase. 1.16; 95% confidence interval [95% CI], 1.03 to 1.31; P=0.01), eGFR (HR per every 1 ml/min per 1.73 m(2) increase, 0.96; 95% CI, 0.94 to 0.97; P<0.001), T2 Oxford classification (tubular atrophy/interstitial fibrosis, >50%; HR, 4.42; 95% CI, 1.40 to 13.88; P=0.01), and C4d-positive staining (HR, 2.45; 95% CI, 1.30 to 4.64; P=0.01).

CONCLUSIONS

C4d-positive staining is an independent risk factor for the development of ESRD in IgAN. This finding is consistent with the possibility that complement activation is involved in the pathogenesis of this disease.

C4d deposits in acute "cell-mediated" rejection: a marker for renal prognosis?

BACKGROUND

Accumulation of C4d along peritubular capillaries (PTC) of renal allografts is normally attributed to antibody-mediated rejection. The prognostic implication of these deposits associated with "cell-mediated" rejection on graft survival remains uncertain. Our study aims to evaluate the impact of C4d deposits along PTC of patients with acute cell- mediated rejection on graft function and survival.

METHODS

We retrospectively analyzed patients transplanted between 2005 and 2010 with histopathologic diagnosis of acute rejection (AR). Eleven patients with "pure" antibody-mediated rejection were excluded. The remaining 79 patients were divided into two groups according to type of AR by Banff 2003 criteria: type I (69.6%) versus type II (30.4%). In each group, comparisons were made between C4d-negative (-) and C4d-positive (+) biopsies.

RESULTS

Fifty-five patients presented with type I AR: 35 (63.6%) C4d- and 20 (36.4%) C4d+. Twenty-four patients presented with type II AR: 13 (54.2%) C4d- and 11 (45.8%) C4d+. In the type I AR group, graft survival at the first and second years was similar in C4d- and C4d+ patients (94% and 91% versus 75% and 75%, respectively, log-rank P = .26). No differences were encountered in estimated glomerular filtration rate (eGFR) between subgroups at the first, second, and final years of follow-up. Graft loss occurred in 14.7% of C4d- patients versus 25% in C4d+ patients (P = NS). In the type II AR group, graft survival at the first and second years was similar in C4d- and C4d+ patients (85% and 85% versus 72% and 61%, respectively, log-rank P = .50). No differences were encountered in eGFR between subgroups at the first, second, and final years of follow-up. Graft loss occurred in 30.8% of C4d- patients versus 45.5% in C4d+ patients (P = NS).

CONCLUSION

Our results suggest that detection of C4d staining in acute "cell-mediated" rejection does not imply a worse renal prognosis.

[Rejection of kidney graft: mechanism and prevention]

Rejection occurs after the introduction of a genetically different graft, in a recipient. Nowadays, it is still a major obstacle in renal transplantation and reflects a normal protective immune response of a recipient against a foreign antigen. Involving many mechanisms of the innate and adaptive immunity, this reaction results in renal parenchymal lesions witch may progress to graft destruction and loss of its function. Several ways are currently used to reduce the action of the immune system and consequently reduce the risk of rejection. After a presentation of the main actors and the sequence of events leading to rejection, we will describe the strategy used by antirejection teams' transplantation. We will successively consider the prevention (pre-transplant immunological assessment, preventive immunosuppressive therapy), the monitoring (search for antibodies, biopsies) and the treatment.

Significance of C4d Banff scores in early protocol biopsies of kidney transplant recipients with preformed donor-specific antibodies (DSA)

The significance of C4d-Banff scores in protocol biopsies of kidney transplant recipients with preformed donor-specific antibodies (DSA) has not been determined. We reviewed 157 protocol biopsies from 80 DSA+ patients obtained at 3 months and 1 year post-transplant. The C4d Banff scores (1,2,3) were associated with significant increments of microcirculation inflammation (MI) at both 3 months and 1 year post-transplant, worse transplant glomerulopathy and higher class II DSA-MFI (p < 0.01). Minimal-C4d had injury intermediate between negative and focal, while focal and diffuse-C4d had the same degree of microvascular injury. A total of 54% of patients had variation of C4d score between 3 months and 1 year post-transplant. Cumulative (3 month + 1 year) C4d scores correlated with long-term renal function worsening (p = 0.006). However, C4d staining was not a sensitive indicator of parenchymal disease, 55% of C4d-negative biopsies having evidence of concomitant MI. Multivariate analysis demonstrated that the presence of MI and class II DSA at 3 months were associated with a fourfold increased risk of progression to chronic antibody-mediated rejection independently of C4d (p < 0.05). In conclusion, the substantial fluctuation of C4d status in the first year post-transplant reflects a dynamic humoral process. However, C4d may not be a sufficiently sensitive indicator of activity, MI and DSA being more robust predictors of bad outcome.

Focal C4d+ in renal allografts is associated with the presence of donor-specific antibodies and decreased allograft survival

Diffuse peritubular capillary C4d deposition in renal allograft biopsies is associated with donor-specific antibodies (DSA) and graft failure. The significance of focal C4d+ is unclear. We reviewed 368 biopsies from 301 patients performed for renal dysfunction or proteinuria over 5 years. Diffuse C4d+, focal C4d+ and C4d- detected by immunofluorescence occurred in 9.5%, 20.9% and 69.4% of biopsies, respectively. Patients were similar in gender, age, cause of renal disease, donor source, HLA mismatch, serum creatinine at baseline and interval from transplantation to biopsy. Diffuse and focal C4d+ were associated with acute cellular rejection (p < 0.001). Transplant glomerulopathy was associated with diffuse C4d+. DSA at the time of biopsy, were positive in 79.3% of diffusely C4d+ patients, 68.8% of those with focal C4d+ (p = 0.27) and 9.9% of patients with C4d- (p < 0.001, compared to either the focal or diffuse groups, respectively). Allograft survival at 40 months was lower in diffuse C4d+ compared to the C4d- group (p = 0.014), but not when compared to the focal C4d+ group. There was a clear trend toward worse graft survival in patients with focal C4d+ in this time interval, but focal C4d+ compared to both diffuse C4d+ and C4d-groups was not statistically significant (p = 0.08).

The use of C3d and C4d immunohistochemistry on formalin-fixed tissue as a diagnostic adjunct in the assessment of inflammatory skin disease

BACKGROUND

Direct immunofluorescent (DIF) testing defines an important diagnostic adjunct in the classification of various inflammatory skin conditions; it requires fresh tissue, a laboratory equipped to perform the procedure, and a pathologist skilled in its interpretation. Although advances have been made in the development of antibodies that can be applied to paraffin-embedded tissue, there has been no reported success on the application of paraffin tissue-based immunohistochemistry as a potential substitute for DIF testing on skin biopsy material.

OBJECTIVE

We applied C3d and C4d immunohistochemistry on paraffin-embedded, formalin-fixed tissue to define a potential application of these two antibodies as a diagnostic adjunct in the evaluation of various inflammatory skin diseases.

DESIGN

A natural language search identified cases submitted for both light microscopic and DIF studies from July 2006 to August 2007. We prospectively included similar cases encountered from August 2007 to March 2008. We correlated the C3d and C4d staining pattern with the DIF and light microscopic findings.

RESULTS

All cases of scarring discoid lupus erythematosus (LE) (20/20) and systemic LE (5/5) showed prominent granular C3d along the dermoepidermal junction (DEJ) and a positive lupus band test result in the latter by DIF. All systemic LE cases demonstrated granular DEJ C4d with C3d or C4d in blood vessels (BV). There was a negative lupus band test result without DEJ C3d or C4d in all cases of subacute cutaneous lupus erythematosus (SCLE) (15/15). There were, however, deposits of C4d within epidermal keratinocytes (7/7), corresponding to IgG decoration of keratinocytes by DIF and the presence of anti-Ro antibodies. Dermatomyositis cases showed prominent mural C3d and C4d in BV corresponding to C5b-9 by DIF (12/12) and one case of hydroxyurea-induced dermatomyositis lacked this staining. Although by DIF all dermatomyositis cases had a negative lupus band test result, 25% of cases showed staining for C3d along the DEJ (3/9). Bullous pemphigoid cases demonstrated homogenous DEJ C3d (17/17) whereas C4d was characteristically negative; there was 100% concordance with linear IgG and C3d by DIF. Eighty two percent of pemphigus cases demonstrated prominent intercellular C3d and C4d, roughly mirroring the intercellular pattern for IgG and complement seen by DIF (9/11). Porphyria cases showed homogeneous and granular C3d (11/11) and C4d (7/11), mirroring the vascular immunoglobulin and C5b-9 by DIF. All cases of urticarial (5), leukocytoclastic (6), and lymphocytic (1) vasculitis exhibited prominent mural C3d and C4d in BV, whereas Henoch-Schönlein purpura (10/10) showed primarily mural BV C3d without C4d, with IgA by DIF. Three cases of relapsing polychondritis showed C3d and C4d within chondrocyte nuclei (3/3), in contrast to negative staining in chondrodermatitis nodularis helicis (0/2). Hypersensitivity reactions were negative for C3d and C4d.

LIMITATIONS

The small sample size in each category is a limitation. The lack of literature precedent with regard to immunohistochemical assessment of extracellular antigens on paraffin-embedded tissue in skin samples is another limitation of this study.

CONCLUSIONS

When correlated with the light microscopic and clinical findings, the C3d and C4d assay has significant application in the assessment of select inflammatory skin diseases including vasculopathic conditions, collagen vascular disease, and autoimmune vesiculobullous disorder. It may prompt further DIF testing or, in some instances, may even define a reasonable substitute for DIF and/or add to the morphologic assessment of a biopsy specimen submitted for routine light microscopic assessment primarily in the setting of autoimmune vesiculobullous disease and collagen vascular disease.

Absence of C4d Deposition in Human Composite Tissue (Hands and Face) Allograft Biopsies: An Immunoperoxidase Study

Deposition of the C4d complement degradation product has been shown to be a marker of antibody-mediated rejection of solid organ allografts, including kidney, heart, liver, and lung. We investigated whether C4d deposition also would be useful in monitoring rejection in human composite tissue allografts. A total of 60 mucocutaneous formalin-fixed, paraffin-embedded and four frozen biopsy specimens from four patients with composite tissue allografts (three hands, one face) taken during a period of 7 days to 7 years after graft were immunostained for C4d by an immunoperoxidase and an immunofluorescence technique, respectively. C4d deposition was not found in any of the specimens studied, even though several of them showed pathological signs of rejection. No human leukocyte antigen alloantibodies were detected in any of the patients during the study period. These results suggest that humoral rejection occurs rarely, if at all, in the setting of human composite tissue allografts.

Thickening of the peritubular capillary basement membrane is a useful diagnostic marker of chronic rejection in renal allografts

In kidney transplantation, the multilayering of the peritubular capillary basement membrane (MLPTC) in electron microscopy (EM) has been recognized as a feature of chronic rejection (CR). In this study, thickening of the peritubular capillary (PTC) basement membrane was evaluated by light microscopy (LM) to determine whether it corresponds to the MLPTC in EM and whether it can be used as a diagnostic marker of CR. Forty-eight patients with late renal allograft were divided into chronic allograft nephropathy (CAN) with CR (Group 1, n = 23), CAN without CR (Group 2, n = 19) and CAN-free (Group 3, n = 6). The thickening of the PTC basement membrane (ptcbm) was scored from grades 0 to 2 (ptcbm score), and the MLPTC thickness was measured in EM. Interobserver agreement on ptcbm scores was statistically significant (Kappa coefficient = 0.63). LM and EM lesions corresponded very well. The ptcbm score was highest in Group 1, and ptcbm2 corresponded closely with CR. Group 1 showed significantly thicker MLPTC than Groups 2 and 3. The results validated the usefulness of the ptcbm score and suggested that the thickening of the PTC basement membrane can be a novel diagnostic marker of CR.

Determinants of poor graft outcome in patients with antibody-mediated acute rejection

This study analyzes the incidence and course of antibody-mediated rejection (AMR) in a cohort of 237 renal transplant patients followed for 30 +/- 20 months. Among these, 32 patients were considered to be at risk for AMR and received intravenous immunoglobulin (IVIg), either as preconditioning (Group A, n = 18) or at the time of transplant (Group B, n = 14). The prevalence of AMR was 27.8% in Group A, 57.1% in Group B and 3.9% in the remainder of the population. Although graft loss remains greater among AMR than for acute cellular rejection (ACR) or the overall transplant population, we have identified a good outcome group (GFR > 15 mL/min/1.73 m(2)) (n = 13), whose renal function at the end of follow-up was comparable to that of the general transplant population. The factors associated with bad outcome are: (1) immunologic: presence and/or persistence of donor-specific anti-HLA antibodies post-transplantation and (2) histologic: neutrophilic glomerulitis, peritubular capillary dilatation with neutrophil infiltrates and interstitial edema at the time of first biopsy; and at the time of late biopsy (3-6 months): lesions of vascular rejection, and monocyte/macrophage infiltrates in glomeruli and dilated peritubular capillaries. Persistence of C4d does not predict outcome. This study outlines for the first time the immunologic and histologic profiles of AMR patients with poor prognosis.

Rescue Therapy by Immunoadsorption in Combination With Tacrolimus and Mycophenolate Mofetil for C4d-Positive Acute Humoral Renal Allograft Rejection

The aim of this study was to investigate the efficacy of immunoadsorption (IA) in combination with tacrolimus (TAC; 0.14 to 0.16 mg/kg/d) and mycophenolate mofetil (MMF; 1.5 to 2.0 g/d) rescue therapy for C4d-positive acute humoral rejection in nine cadaveric renal allograft recipients. Initial Panel reactive antibody (PRA-I and PRA-II levels were as high as 28.8% +/- 16.2% and 15.3% +/- 8.9%, IA therapy significantly decreased PRA-I and PRA-II levels to 5.9% +/- 2.9% and 2.2% +/- 0.6%, respectively. Total serum immunoglobulin levels were markedly decreased. Repeated allograft renal biopsy in nine patients revealed remission of acute humoral rejection (AHR), and the deposition of C4d disappeared and reduced. With a mean follow-up of 29.4 +/- 5.4 months, patient and allograft survivals were 100%, and renal function remained stable with a mean serum creatinine of 1.1 +/- 0.3 mg/dL. Our findings suggested that a therapeutic approach combining IA and TAC and MMF rescue improved the outcomes of AHR.

Biologics in the prevention and treatment of graft rejection

Biologics are used in solid organ allografting and hematopoietic stem cell transplantation (HSCT) for the induction and maintenance of immunosuppression. In solid organ transplantation, antibodies targeting T cells are part of induction protocols administered for initiation of immunosuppression during organ transfer and during sustained post transplant periods for prevention of graft rejection. Several clinical trials in renal allografting provide data for the efficacy and safety of biologics in this clinical setting. Application of biologics also allows the reduction of calcineurin inhibitors, thereby reducing toxicity and improving long-term graft function. In acute rejection periods, anti T cell antibodies are established in steroid-resistant cases. Strategies interfering with the activity of soluble cytokines are less frequently applied for solid organ transplantation. In HSCT, T cell directed antibodies as part of conditioning protocols improve engraftment and reduce the incidence of detrimental graft vs host disease (GvHD). In acute GvHD, both antibodies targeting T cells and cytokines like TNF-alpha are established therapeutics for remission induction.

Comparison of C4d Immunostaining Methods in Renal Allograft Biopsies

Immunostaining of renal allograft biopsies for C4d deposition has become an important diagnostic tool in the recognition of humoral-mediated graft rejection. The majority of studies have been performed on frozen tissue sections with one of several commercially available antibody reagents. However, only a single small series that compared reagents or methods, including staining of formalin-fixed, paraffin-embedded tissue, has been published. Two different staining methods in 138 renal allograft biopsies were compared directly: A mAb (Quidel, San Diego, CA) on frozen tissue sections with indirect immunofluorescence (IF) and a polyclonal antibody (Biomedica Gruppe, distributed by ALPCO, Windham, NH) applied to formalin-fixed, paraffin-embedded tissue with immunohistochemical (IHC) detection. An initial data set of 107 consecutive cases showed complete agreement between staining methods in 104 (97%) cases. Overall, nine of 107 cases were positive with one or both methods, representing 8.4% of all allograft biopsies tested, 15% of clinically indicated biopsies, and 24% of biopsies with a histologic diagnosis of acute cellular rejection. A second set of 31 cases included 17 cases that were positive by either method, with concordance in 29 of 31 cases. Combining the two data sets, the overall specificity of the IHC method compared with IF was 98%, and sensitivity was 87.5%. Direct comparison demonstrates that IHC staining of formalin-fixed, paraffin-embedded tissue with anti-C4d polyclonal antibody has acceptable sensitivity and specificity, as compared with IF staining of frozen tissue with the Quidel mAb.

Focal peritubular capillary C4d deposition in acute rejection

BACKGROUND

Diffuse peritubular capillary (PTC) C4d deposition has been shown to be associated with relatively poor graft outcome. The significance of focal PTC C4d staining in the early post-transplant period is uncertain.

METHODS

Sixty-five biopsies from 53 patients with acute rejection were graded (Banff '97 criteria), stained for C4d, monocytes and T cells, and divided into three groups according to PTC C4d: (i) focal C4d (F) (14 biopsies, 14 patients), (ii) diffuse C4d (D) (23 biopsies, 15 patients) and (iii) no C4d (N) (28 biopsies, 24 patients). The three groups were compared with respect to a variety of biopsy and clinical parameters including outcome.

RESULTS

The incidence of transplant glomerulitis and glomerular monocyte infiltration were significantly greater in F (64% and 2.0+/-2.0) and D (57% and 3.4+/-2.0) than in N (11% and 0.2+/-0.2). A significantly higher proportion of F (93%) demonstrated acute cellular rejection (Banff '97 grade > or = 1A) than did D (35%). The F and D groups included significantly more females (50 and 67%, respectively) than did N (21%). The percentage of patients with a second or third transplant was higher in F (29%) and D (40%) than in N (8%) (P = 0.0589). The proportion of patients with glomerular filtration rate < 30 ml/min at 12, 24 and 48 months was higher in the D and F groups than in the N, and there was a statistically significant increasing trend in odds of this outcome occurring at 48 months across the three groups (D > F > N group) (P = 0.0416).

CONCLUSION

The results suggest that the biopsy findings and clinical course in patients with focal PTC C4d staining are similar to those associated with diffuse C4d.

C4d Complement Split Product in Diagnosis of Immunological Activity of Chronic Allograft Nephropathy

INTRODUCTION

Activation of the humoral branch of the immunological response is currently believed to play an important role in pathogenesis of chronic allograft nephropathy. The impact of humoral alloreactivity, indicated by the presence of C4d deposits in peritubular capillaries of a renal allograft, on the development of chronic allograft nephropathy is a significant problem in transplantation. The aim of the study was to assess and correlate C4d expression in patients with chronic allograft nephropathy, with clinical and morphological variables, as well as to assess the impact of a change in immunosuppression regimen on posttransplant course and renal allograft morphology.

PATIENTS AND METHODS

Twenty-six patients with chronic allograft nephropathy underwent biopsies to correlate C4d expression with clinical parameters and morphological findings. In all patients azathioprine was replaced with mycophenolate mofetil with additional CsA dose reduction in 12 patients. After 1 year, 14 protocol biopsies were performed.

RESULTS

The frequency of C4d peritubular capillary deposition among patients with chronic allograft nephropathy was 30%. C4d expression appeared later after transplantation, was correlated with chronic allograft glomerulopathy and proteinuria but not other clinical or histological variables. C4d deposits displayed no independent impact on serum creatinine level. Proteinuria was significantly more reduced in the C4d(+) group. Progression of chronic morphological changes was significantly accelerated in the C4d(+) group.

CONCLUSION

C4d peritubular capillary expression did not differentiate patients after immunosuppression enhancement, but it predisposed to progression of chronic morphological findings during 1-year observation.

Humoral rejection of organ allografts

In recent years, the deleterious clinical consequences of recipient de novo alloantibody production against HLA antigens from human organ allografts have been extensively investigated. In kidney transplantation, the identification of the complement C4d fragment in peritubular capillaries as a specific marker for humoral rejection has helped to define and characterize distinct clinical alloantibody-mediated syndromes. This knowledge is relevant for patient management as new therapeutic strategies to remove and control anti-donor antibody production, particularly in the setting of acute humoral rejection, have been reported. For recipients of nonrenal organ allografts such as heart transplant recipients, de novo anti-HLA alloantibody may also be important, although more studies are needed before clear guidelines can be proposed.

Incidence of C4d stain in protocol biopsies from renal allografts: results from a multicenter trial

C4d staining of renal allografts is regarded as an in situ marker of active humoral rejection. Few data are available about the incidence of C4d deposition in protocol biopsies compared to indication biopsies. To evaluate whether center-specific factors influence the incidence of C4d detection, we performed a multicenter study. From three European centers, 551 protocol and 377 indication biopsies were reclassified according to the updated Banff criteria and stained for C4d. C4d results were recorded as diffuse or focal positive and statistically correlated to clinical parameters, morphology and graft survival. In the protocol biopsies, a diffuse C4d stain was found in 2.0%, and a focal stain in 2.4%. In indication biopsies, 12.2% were diffusely and 8.5% focally C4d positive (protocol:indication p < 0.0001). The incidence of C4d deposition varied significantly between centers, attributable to variable numbers of presensitized patients with more C4d positive indication and protocol biopsies. Diffuse and focal C4d stain correlated with morphology of humoral rejection in protocol as well as in indication biopsies. Protocol biopsies show a significantly lower incidence of C4d deposition than indication biopsies. Subclinical C4d detection in protocol biopsies had no significant impact on allograft survival in our series.

Intravenous Immunoglobulin and Plasmapheresis in Acute Humoral Rejection: Experience in Renal Allograft Transplantation

Acute humoral rejection (AHR) in kidney transplantation is associated with higher rates of allograft loss when compared with acute cellular rejection (ACR). Treatment with intravenous immunoglobulin (IVIG) combined with plasmapheresis (PP) has been used recently in many centers. We report the incidence, clinical characteristics, and outcome of patients with AHR treated with IVIG and PP. All patients (n=519) at our institution who underwent kidney transplantation between January 1999 and August 2003 were retrospectively analyzed and classified according to biopsy results into three groups: AHR, ACR, and no rejection. AHR was diagnosed in 23 patients (4.5%) and ACR in 75 patients (15%). Mean follow-up was 844+/-23 days. Female sex, black race, and high panel-reactive antibody were risk factors for AHR. Most AHR patients (22 of 23) were treated with IVIG and PP. Two-year graft survival was numerically worse in patients with AHR versus ACR (78% vs. 85%, p=0.5) but the difference was not statistically significant. Graft survival after AHR treated with IVIG and PP is much better than it has been historically. IVIG in combination with PP is an effective treatment for AHR. Graft survival in this setting is similar to graft survival in patients with ACR.

Development of Posttransplant Antidonor HLA Antibodies Is Associated with Acute Humoral Rejection and Early Graft Dysfunction

BACKGROUND

The goal of this study was to determine whether the production of posttransplant antibodies directed against donor HLA mismatches (donor specific antibody; DSA) is associated with renal allograft rejection and early graft dysfunction.

METHODS

Forty-nine adult renal allograft recipients with increased risk of rejection were enrolled during the period of October 2001 through May 2003 and were prospectively monitored for the development of anti-HLA antibodies.

RESULTS

Of 49 patients, eight (16.3 %) patients were diagnosed with acute humoral rejection (AHR) and 11/49 (22.4%) patients were diagnosed with acute cellular rejection (ACR). A strong association between pretransplant HLA sensitization and AHR was found (P=0.005). Of the eight patients diagnosed with AHR, the majority developed DSA before or concomitant with episodes of rejection (P<0.001). Only 3 of 41 patients (7.3%) without AHR developed DSA. The pathogenic role of alloantibodies was further substantiated by analyzing their association with graft function as measured by serum creatinine levels. The average serum creatinine after the third month posttransplantation in DSA producers was 2.24+/-1.01 mg/dL, while in non-DSA patients the average serum creatinine was 1.41+/-0.37 mg/dL (P<0.01).

CONCLUSION

This study reveals a strong association between the production of DSA, AHR, and early graft dysfunction. Our findings indicate that prospective monitoring for anti-HLA antibodies following transplantation is a useful test for the diagnosis and classification of AHR for identifying patients at risk of early graft dysfunction.

Novel rescue therapy for C4d-positive acute humoral renal allograft rejection

OBJECTIVE

To investigate the efficacy of immunoadsorption (IA) in combination with tacrolimus (TAC) and mycophenolate mofetil (MMF) rescue therapy for C4d-positive acute humoral rejection (AHR) of renal transplants.

METHODOLOGY

Six of 185 cadaveric renal allograft recipients transplanted at our institute developed AHR over a mean period of 4.8 +/- 0.8 d after operation. The ages ranged from 35 to 51 yr (mean 42.6 +/- 5.6 yr). C4d deposits in peritubular capillaries (PTC) and accumulation of granulocytes in PTC were observed. IA with staphylococcal protein A and TAC-MMF combination therapy were given.

RESULTS

After subjected to IA for 6.3 +/- 1.03 sessions combined with TAC (0.14-0.16 mg/kg/d) and MMF (1.5 g/d) therapy, renal function recovered in all the patients. The mean duration of treatment when serum creatinine decreased was 14 +/- 2.9 d. The pre-IA panel reactive antibody reactivity was as high as 50.2 +/- 6.1%, and was significantly reduced to 8.3 +/- 2.9% after IA. Repeated allograft kidney biopsy in four of six patients revealed a favorable remission of AHR. With a mean follow-up of 18.8 +/- 5.46 months, patient and allograft survival are 100%, renal function remained stable with a mean serum creatinine of 1.2 +/- 0.22 mg/dL.

CONCLUSION

The optimal treatment for alloantibody-mediated AHR remains undefined. Our findings suggest that a therapeutic approach combining IA and TAC-MMF rescue has excellence to improve the outcome of AHR.

Injury and progressive loss of peritubular capillaries in the development of chronic allograft nephropathy

BACKGROUND

Chronic allograft nephropathy (CAN) remains the most important cause of late renal graft loss. However, the mechanism for graft dysfunction and the process of the development of CAN are not well understood. This study examined the role of microvascular injury in the development of CAN.

METHODS

We studied renal biopsies obtained from grafts with CAN (N= 79) and pretransplant control kidneys (N= 20). Microvascular injury was examined morphologically, and was correlated with interstitial fibrosis, glomerular sclerosis, graft function, and the severity of CAN. The humoral and cellular immunity involved in CAN were examined by C4d, CD3, and TIA-1 staining.

RESULTS

In all the cases of CAN, microvascular injury was evident with or without CD3-positive T cells, TIA-1-positive cytotoxic cells, and/or C4d+ complement deposition. Irrespective of chronic rejection (N= 14), C4d+ chronic humoral rejection (N= 6), or other CAN, the development process of CAN was characterized by injury and progressive loss of identifiable peritubular capillaries (PTCs) accompanied with the development of interstitial fibrosis. Injured PTCs were characterized morphologically by the process of angioregression with the presence of apoptotic cells, lamination of the basement membrane, and loss of PTCs. The low number of PTCs correlated significantly with the severity of CAN (r=-0.74, P < 0.001), the development of interstitial fibrosis (r=-0.75, P < 0.001), graft dysfunction (r=-0.69, P < 0.001), and also correlated weakly with proteinuria (r=-0.45, P < 0.05). In the glomeruli, capillary loss significantly correlated with the degree of glomerular sclerosis (r=-0.66, P < 0.001) and proteinuria (r=-0.65, P < 0.001), but did not correlate with the severity of CAN (r=-0.24, P > 0.05) or graft dysfunction (r=-0.32, P > 0.05).

CONCLUSION

CAN was characterized by progressive injury to the renal microvasculature and the development of renal scarring. In particular, injury, angioregression and progressive loss of the PTC network strongly contributed to the development of interstitial fibrosis and graft dysfunction in CAN, and might play a crucial role in the development of CAN.

C4d-positive acute humoral renal allograft rejection: Rescue therapy by immunoadsorption in combination with tacrolimus and mycophenolate mofetil

OBJECTIVE

We investigated the efficacy of immunoadsorption (IA) in combination with tacrolimus (FK506) and mycophenolate mofetil (MMF) rescue therapy for C4d-positive acute humoral rejection (AHR) of renal transplants.

METHODS

Six of 185 cadaveric renal allograft recipients developed AHR at a mean of 4.8 +/- 0.8 days after the operation. C4d deposits were observed in peritubular capillaries (PTC) with accumulation of granulocytes. IA with staphylococcal protein A and FK506-MMF combination therapy were administered.

RESULTS

After treatment with IA for 6.3 +/- 1.03 sessions combined with FK506 (0.14 to 0.16 mg.kg(-1).d(-1)) and MMF (1.5 g/d) therapy, renal function recovered in all the patients. The mean duration of treatment to a serum creatinine decrease was 14 +/- 2.9 days. The pre-IA panel reactive antibody reactivity (PRA) peaked at 50.2% +/- 6.1%, and was significantly reduced to 8.3% +/- 2.9% after IA. In four of six patients repeat allograft biopsy revealed a remission of AHR. With a mean follow-up of 18.8 +/- 5.46 months, patient and allograft survival are 100% and renal function remains stable with a mean serum creatinine of 1.2 +/- 0.22 mg/dL.

CONCLUSION

The optimal treatment for alloantibody-mediated AHR remains uncertain. Our findings suggest that a therapeutic approach combining IA and FK506-MMF rescue improves the outcome of AHR.

Histological analysis of late renal allografts of antidonor antibody positive patients with C4d deposits in peritubular capillaries

The association of humoral immunity with late renal allograft dysfunction has recently been recognized, and many reports have revealed C4d deposits in peritubular capillaries (C4d in PTC), and the presence of serum antidonor HLA antibody in patients suffering from graft dysfunction, long time after transplantation. In this study, morphological changes in renal allograft biopsies more than 1 year after transplantation in 14 patients with C4d in PTC and serum antidonor antibody were investigated for the presence of chronic rejection (CR). In addition to the light microscope study, an electron microscope study was done to evaluate the multilayering of the peritubular capillary basement membrane (MLPTC). Histologically, only seven of 14 patients met the criteria of CR, and 71.4% (5/7) of CR patients had episodes of acute humoral rejection (AHR), coexisting with acute tubulointerstitial rejection. Peritubular capillaritis was observed in all patients, although it differed in severity. Transplant glomerulitis and interstitial inflammation were also observed in many patients: 71.4% (10/14) and 92.9% (13/14) respectively. MLPTC was observed in 12 patients (85.7%), but the severity of the MLPTC did not reflect the severity of peritubular capillaritis or any other histological features. The long-term outcomes of the patients CR, especially those with episodes of AHR, were poor, and two of them lost their graft functions. On the other hand, patients without CR had relatively favourable outcomes. In conclusion, we confirmed the diverse morphological changes of late renal allografts, which cannot be categorized as chronic humoral rejection (CHR), and such patients who do not have typical morphological changes such as CHR, should be followed-up on a long-term basis in order to clarify the significance of C4d on PTC in late renal allografts.

Evidence that humoral allograft rejection in lung transplant patients is not histocompatibility antigen-related

We have recently recognized humoral rejection (HR) in lung allograft recipients and its association with acute and chronic graft dysfunction. We have shown that C4d, a stable marker of classic complement activation, is deposited in lung allografts, correlating with clinical rejection and parenchymal injury. The antigenic target may be endothelium in the setting of recurrent acute rejection while varying components of the bronchial wall may be important in chronic graft dysfunction. We sought to establish whether there is a role for antibodies with histocompatibility antigen specificity in the lung humoral allograft phenomenon. Flow cytometric and ELISA assays to assess donor-specific antigens were conducted on sera from 25 lung transplant recipients who had experienced one or more episodes of clinical rejection; in addition, the serum samples were tested for evidence of antiendothelial cell antibody activity. Morphologically, each case had biopsies showing septal capillary injury with significant deposits of immunoreactants with microvascular localization and positive indirect immunofluorescent antiendothelial cell antibody assay. Panel-reactive antibody testing showed absence of MHC Class I/II alloantibodies; ELISA based crossmatch detecting donor-specific MHC Class I/II specific antibodies was negative. HR can occur in the absence of antibodies with HLA specificity; antigenic targets may be of endothelial cell origin.

C4d complement split product expression in chronic rejection of renal allograft

Chronic allograft rejection remains the major cause of late renal graft loss. Its pathogenesis is complex, depending on both immunological and nonimmunological factors. An important role in development of chronic rejection is ascribed to an ongoing immunological reaction mainly of the humoral type. C4d complement split product, as a stable fragment of complement degradation activated by antigen-antibody complexes, is considered to be an indicator of humoral activity in allografts. The aim of the present study was to establish a correlation between C4d expression and morphological findings specific for chronic rejection among biopsy specimens from patients with deteriorating graft function versus protocol biopsy specimens versus biopsy specimens of native kidneys with glomerular diseases. C4d deposits in peritubular capillaries and glomeruli were observed in 83% of patients with morphological changes of chronic rejection. No C4d expression was found in the protocol biopsy group. C4d deposits in glomeruli localizations were found in kidneys from patients with glomerulopathies; the pattern of distribution was similar to that for antibodies characteristic for glomerulonephritis. There was a positive correlation between C4d expression and morphological features of chronic rejection. In our opinion, only peritubular capillary localization is specific for a rejection process; glomerular localization is nonspecific and probably secondary to antigen-antibody complex deposition in course of some types of glomerulopathies.

Humoral theory of transplantation

According to the humoral theory of transplantation, antibodies cause allograft rejection. Publications are cited showing that antibodies: (1). cause hyperacute kidney rejection, (2). lead to C4d deposits associated with early kidney graft failures, (3). are a good indicator of presensitization leading to early acute rejections, (4). were present in 96% of 826 patients who rejected a kidney graft, (5). are associated with chronic rejection in 33 studies of kidney, heart, lung and liver grafts, and (6). in three studies, appeared in the circulation BEFORE evidence of bronchiolitis obliterans in lung transplants, and BEFORE kidney rejection. In addition, a prospective cooperative study of 1629 patients in 24 centers demonstrated that antibodies foretold subsequent failures after a follow-up period of 6 months (p = 0.05). The specificity of antibodies detected in the serum of rejecting patients were often not donor specific, presumably because they were absorbed by the rejecting organ. If the humoral theory is accepted, even provisionally, transplanted patients who have antibodies could be treated with immunosuppression until the antibodies disappear to determine whether chronic rejection can be blocked. If successful, in patients who do not have antibodies, immunosuppression could be reduced until antibodies appear.

Beneficial effect of plasmapheresis and intravenous immunoglobulin on renal allograft survival of patients with acute humoral rejection

BACKGROUND

Acute humoral rejection (AHR) has been associated with enhanced graft loss. Our study compared the renal allograft survival of patients with AHR treated with plasmapheresis (PP) and intravenous immunoglobulin (IVIG) with allograft survival in patients with acute cellular rejection (ACR).

METHODS

We retrospectively analyzed all kidney transplants performed at our institution between January 1999 and August 2001 (n=286). Recipients were classified into three groups according to biopsy reports: AHR, ACR, or no rejection. The ACR group was further divided into early and late rejection (<90 and >90 days posttransplant, respectively).

RESULTS

After a mean follow-up of 569+/-19 days, the incidence of AHR was 5.6% (n=16). Recipient presensitization, delayed graft function, early rejection, and higher creatinine at diagnosis were characteristic of AHR. Most AHR patients (14/16) were treated with PP and IVIG. One patient received only IVIG, whereas another received only PP. All AHR patients were given steroid pulses, but only four received antilymphocyte therapy because of concomitant severe ACR. The ACR group comprised 43 patients (15%). One patient with mild rejection received no therapy, 20 improved with steroids alone, and 22 required additional antilymphocyte therapy. One-year graft survival by Kaplan Meier analysis was 81% and 84% in the AHR and ACR groups, respectively (P=NS). Outcomes remained similar when AHR patients were compared with those with early ACR.

CONCLUSIONS

We conclude that AHR, when diagnosed early and treated aggressively with PP and IVIG, carries a short-term prognosis that is similar to ACR.