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 deposition in allografts: current concepts and interpretation

Alloantibody responses are not prevented by the latest immunosuppressive regimens and contribute to increased early and late renal allograft graft loss. Numerous papers have set forth the clinical, pathological, and immunopathological features of acute humoral rejection, in particular the strong correlation between the presence of C4d deposition and circulating antidonor HLA class I and class II antibodies. Humoral rejection also occurs in a chronic setting, associated with chronic allograft glomerulopathy and arteriopathy. C4d deposition can also be found in stable grafts without concurrent graft pathology, a finding that may indicate accommodation. The central diagnostic criterion for humoral rejection is the demonstration of C4d in peritubular capillaries. The criteria for humoral rejection are not as widely accepted for other organs, such as the heart, lung, and pancreas, although humoral rejection, including C4d deposition, has been described. This review focuses on the practical aspects of this test, particularly as applied routinely in renal allografts since 1998 in our laboratory.     

Association of Humoral Immunity and Bronchiolitis Obliterans Syndrome

Animal studies have shown that blockade of complement may reduce the severity of and/or prevent the development of bronchiolitis obliterans syndrome (BOS), suggesting a role for complement activation. We explored the hypothesis that humoral immunity plays a role in the evolution of BOS. Thirteen unilateral lung transplant patients with BOS defined the patient population. Fresh frozen tissue was analyzed for deposition of C1q, C4d, C5b-9 and immunoglobulin (IgG, IgM, IgA). An indirect immunofluorescent assay was also conducted with patient serum against cytospins of the pulmonary endothelium. In each case the biopsies showed a microvascular injury syndrome involving the bronchial wall characterized by one or more of hemorrhage, fibrin deposition, and endothelial cell necrosis. Other features included bronchial epithelial and chondrocyte necrosis. The end-stage lesion was a thinned bronchial epithelial lining mural fibrosis. Immunofluorescent analysis showed deposition of C1q, C3, C4d, C5b-9, and immunoglobulin in the bronchial epithelium, chondrocytes, basement membrane zone of the bronchial epithelium, and bronchial wall microvasculature. The indirect antiendothelial cell antibody assay was positive in all tested. Humoral immunity may play a role in the pathogenesis of BOS; the antigenic targets include the bronchial wall microvasculature, bronchial epithelium, and chondrocytes.     

C4d deposition in early renal allograft protocol biopsies

BACKGROUND: Deposition of the complement protein C4d in renal allograft biopsies obtained during graft dysfunction and rejection has been proposed to be a sensitive marker of antibody-mediated acute rejection. To determine the diagnostic specificity of C4d deposition, it is important to study biopsies from allografts with no evidence of dysfunction. In this study, we examined C4d deposition in protocol biopsies obtained irrespective of clinical status. METHODS: Immunohistochemistry for C4d was performed on routine protocol biopsies preimplantation and on day 7 posttransplantation from 48 unselected renal allografts. Serum samples obtained up to 1 month after transplantation were assayed for donor-reactive antibodies (DRA). Results were correlated with histopathology and clinical outcome measures. RESULTS: Diffuse C4d deposition was detected in the peritubular capillaries of 6 of 48 (13%) biopsies. C4d deposition was present in 5 of 15 (33%) biopsies that showed acute rejection (Banff 97, category 4) but only in 1 of 33 (3%) biopsies with no rejection (P=0.003, 97% specificity). Posttransplant DRAs were detected in 21 of 48 (44%) patients. All five recipients with C4d deposition and rejection had posttransplant DRA; the recipient whose biopsy showed C4d positivity, but not rejection, did not have detectable DRA. C4d deposition was not treated with plasmapheresis or intravenous immunoglobulin and was not associated with poor posttransplant graft outcome at 1-year follow-up. CONCLUSIONS: Our results show that in early posttransplant protocol biopsies, C4d is a specific marker for the presence of humoral rejection, as indicated by its association with DRA and acute histologic rejection.     

肾移植一年后急性排斥反应时移植肾组织中C4d表达阳性的临床研究

目的 观察肾移植1年后发生急性排斥反应时移植肾组织中补体片段C4d的表达情况,分析其对移植肾功能及预后的影响.方法 选择肾移植时间超过1年,临床诊断为急性排斥反应并经病理穿刺活检证实的肾移植受者36例为研究对象.以第1例受者移植肾组织穿刺时间为观察起点(2006年3月),以此项研究结束时间为观察终点(2010年4月).应用C4d多克隆抗体对移植肾穿刺组织行免疫组织化学染色,检测C4d在移植肾组织中的表达情况;根据检测结果,分为C4d阳性组和阴性组,分析和比较两组在观察时间段内移植肾功能的变化及存活时间.结果 在36例受者的移植肾穿刺标本中,C4d阳性16例(44.4%),C4d阴性20例(55.6%);C4d阳性组和阴性组移植肾组织中嗜酸性粒细胞浸润数量分别为(9.4±4.5)个和(2.6±1.8)个,两组比较,差异有统计学意义(P＜0.05).在观察时间段内,所有受者血清肌酐均有不同程度上升,但C4d阳性组上升幅度与C4d阴性组比较,差异无统计学意义(P＞0.05);C4d阳性组和C4d阴性组受者移植肾功能丧失率分别为31.3%(5/16)和30.0%(6/20),两组比较,差异无统计学意义(P＞0.05).C4d阳性组和C4d阴性组受者移植肾穿刺后的巾位存活时间分别为(19.3±5.3)个月和(22.5±7.4)个月,两组比较,差异无统计学意义(P＞0.05).结论 肾移植1年后发生急性排斥反应时,移植肾组织中C4d表达阳性对其功能及存活时间无明显影响.     

Acute Humoral Rejection of Human Lung Allografts and Elevation of C4d in Bronchoalveolar Lavage Fluid

Antibody-mediated rejection is well established for renal allografts but remains controversial for lung allografts. Cardinal features of antibody-mediated rejection in renal allografts include antibodies to donor human leukocyte antigen (HLA) and evidence for antibody action, such as complement activation demonstrated by C4d deposition. We report a lung allograft recipient with circulating antibodies to donor HLA who failed treatment for acute cellular rejection but responded to therapy for humoral rejection. To address the second criteria for antibody-mediated rejection, we determined whether complement activation could be detected by measuring C4d in bronchoalveolar lavage fluid (BALF) by ELISA. Airway allergen challenge of asthmatics activates the complement pathway; therefore, we used BALF from asthmatics pre- and post-allergen challenge to measure C4d. These controls demonstrated that ELISA could detect increases in C4d after allergen challenge. BALF from the index patient had elevated C4d concomitant with graft dysfunction and anti-donor HLA in the absence of infection. Analysis of BALF from 25 additional lung allograft recipients showed that C4d concentrations >100 ng/mL were correlated with anti-HLA antibodies (p = 0.006), but were also observed with infection and in asyptomatic patients. The findings support the occurrence of anti-HLA-mediated lung allograft rejection and suggest that C4d measurement in BALF may be useful in diagnosis.     

Three-year outcome of isolated glomerulitis on 3-month protocol biopsies of donor HLA antibody negative patients

Transplant glomerulitis (TG) can lead to the diagnosis of acute humoral rejection when associated with C4d. Recent data have shown that, in patients with donor-specific antibodies, TG is a sign of humoral rejection, even in the absence of C4d. However, the clinical significance of isolated TG, i.e. TG without C4d deposition or morphological evidence of rejection, has not been specifically studied in protocol biopsies of recipients without donor-specific antibodies. We compared 20 isolated TG-patients with 44 selected recipients without TG or any rejection-associated change. The two groups had similar baseline characteristics. After a 3 year follow-up, renal function, acute rejection rate, and development of HLA antibodies were not significantly different between the two groups. Isolated TG had no deleterious consequences on the 3 year graft outcome. Eleven patients of the glomerulitis-group had another allograft biopsy during follow-up: glomerular lesions returned to normal in six patients whereas the persistence of glomerulitis or features consistent with chronic transplant glomerulopathy were noticed in the remaining five patients. Four of these five patients had pretransplant non-donor specific HLA antibodies. In conclusion, although isolated TG had no impact on allograft function at 3 year, histological outcome could be related to patient sensitization.     

Significance of C4d deposition in the diagnosis of rejection after liver transplantation

C4d immunohistochemical staining of liver allograft biopsies was performed to assess its relationship to other pathological changes in the liver. C4d deposition was detected in 69.2% of liver graft biopsies from patients under going rejection, 33.3% of liver graft biopsies from patients with hepatitis B relapse after transplantation, and 28.6% of liver biopsies from patients with hepatitis B. When rejection occurred C4d deposition was located in the vascular walls of portal areas and hepatic sinusoidal walls. Examination of biopsies from patients with hepatitis B relapse after transplantation or hepatitis B infection showed C4d deposition only in the vascular walls of the portal area. C4d deposition in both vascular walls of portal area and hepatic sinusoidal walls was detected in only one of 12 ischemia-reperfusion damage cases. Repeated biopsy of the same patient 1 month later revealed acute cellular rejection. No C4d deposition was found in biopsies from a patient with bile duct occlusion after liver transplantation. C4d might serve as a sensitive marker for the diagnosis of liver rejection.     

A retrospective study of plasma cell infiltrates in explanted renal allografts

Renal transplantation is the most effective therapy in end-stage renal disease. The prognosis for transplant survival is still determined by rejection. When plasma cells predominate in the cellular infiltrate of allografts in rejection, it is called plasma cell-rich rejection, which has a poor prognosis. To study the correlation between plasma cell infiltration and humoral rejection, and to explore whether the local plasma cells were involved in renal allograft loss we analyzed 40 explanted grafts and 20 specimens removed for other diseases. All specimens were embedded, deparaffined, and stained with hematoxylin eosin (HE) for analysis by immunohistochemistry (IH). Renal allograft rejection was classified according to the Banff 1997 criteria with examinations for C4d deposition and CD138 expression. Positive C4d staining was defined by linear endothelial C4d deposition in > or =25% of cortical peritubular capillaries. The specimens designated as CD138-positive demonstrated strong and diffuse staining characteristics; trace or rare CD138-positive were classified as negative. Our results showed that among 40 renal graft specimens, 17 cases were C4d-positive, 23 cases were CD138-positive, and 13 cases were C4d and CD138 double-positive, namely, 42.5%, 57.5%, and 32.5%, respectively. Among the double-positive cases, there were 2 patients with a diagnosis of acute cellular rejection, 1 with hyperacute rejection, and 10 with chronic humoral rejection. C4d deposition and CD138-positive plasma cell infiltrate were related by a Spearman analysis (r = 0.330; P = .038). In the control group, there was only 1 case showing C4d positive activities. These observations suggested that infiltrated plasma cells in the renal allograft probably participate in humoral rejection through local secretion of antibodies.     

Pulmonary Capillaritis as a Manifestation of Acute Humoral Allograft Rejection Following Infant Lung Transplantation

Pulmonary capillaritis has been described in adult lung transplant recipients, but has not been previously reported in pediatric recipients. We report a case of posttransplant pulmonary capillaritis in an 8-month-old infant, and demonstrate evidence of C4d deposition and B-lymphocytes in the allograft, donor anti-HLA antibodies in the serum and a clinical and immunohistochemical response to anti-CD20 monoclonal antibody (rituximab) therapy. These findings strongly support the hypothesis that pulmonary capillaritis may represent a form of acute humoral rejection in the lung allograft that is less common than, and clinically and histologically distinct from, typical acute cellular rejection.     

Acute humoral rejection and C4d immunostaining in ABO blood type-incompatible liver transplantation.

Complement C4d deposition in graft capillaries has been reported to be associated with antibody-mediated rejection in kidney and other solid organ transplantation. The correlation of C4d deposits and humoral rejection in liver transplants, however, is not well understood. We investigated the C4d immunostaining pattern in 34 patients whose liver biopsy was taken within the first 3 postoperative weeks for suspected acute rejection after ABO blood type-incompatible liver transplantation. The staining pattern was classified as positive (portal stromal staining), indeterminate (endothelial staining only), and negative (no staining). Positive C4d immunostaining was seen in 17 (50%) patients and was significantly associated with high (x64 or more) postoperative antidonor A/B antibody (immunoglobulin M (IgM)) titers (88 vs. 35%, P = 0.002) and poorer overall survival rate (41 vs. 88%, P = 0.007). Ten of 11 (91%) cases with histological acute humoral rejection (periportal edema and necrosis (PEN) or portal hemorrhagic edema) were positive for C4d, all of which showed high postoperative antibody titers. The other histologies associated with C4d positivity was purulent cholangitis (n = 4), coagulative hepatocyte necrosis (n = 1), acute cellular rejection (n = 1), and hepatocanalicular cholestasis (n = 1). Full clinical recovery was observed in only 6 of 17 (35%) C4d-positive patients, and tended to be associated with a lower rejection activity index (RAI). In conclusion, our study indicates that C4d deposits in the portal stroma can be a hallmark of acute humoral rejection in ABO-incompatible liver transplantation, and allograft damage can be reversible in a minority of cases.     

Incidence and importance of c4d deposition in renal allograft dysfunction

Recent studies showed that peritubular capillary deposition of C4d is a marker of humoral immune responses directed against a renal allograft. The aim of this retrospective study was to investigate the incidence, clinical features, and prognostic implications of C4d deposition in renal allograft biopsy specimens. The biopsies had been performed due to acute graft dysfunction. This study of 104 renal allograft biopsies performed in 2004 classified histopathological findings according to Banff criteria. All paraffin-embedded biopsy samples were stained with an immunohistochemical method for C4d deposition. Demographic data, clinical findings, and biochemical findings were obtained from patients' charts. C4d staining was positive in 15/104 (14%) samples. The staining pattern was diffuse in 8 and focal in 7 patients. Nine patients were males. The overall mean age was 33 +/- 6 years. Ten received live-donor grafts. The biopsy occurred at a mean of 1007 +/- 1415 (range, 15-4712) days after the operation with a mean serum creatinine (SCr) level of 2.8 +/- 1.5 (1.25-6.0) mg/dL. Patients were divided into 2 groups according to the occurrence time: early (before 100 days) and late (after 100 days). Among the early group (n = 5), the mean SCr level was 2.8 +/- 1.5 mg/dL; a diffuse staining pattern was seen in 4 (80%) patients. Histological findings were acute rejection in 3, borderline changes in 1, or thrombotic microangiopathy in 1 patient. Two patients were treated with pulse steroids and 3 with ATG, intravenous immunoglobulin, and plasmapheresis. Three patients lost their grafts at the mean of 118 +/- 100 days after the biopsy. In the late group (n = 10), the mean SCr level was 2.8 +/- 1.7 mg/dL with a diffuse staining pattern in 4 (40%) patients. The histological findings included acute rejection in 6, chronic vascular rejection in 2, thrombotic microangiopathy in 1, and chronic allograft nephropathy in 1 patient. Six patients were treated with pulse steroids, and 3 with ATG and intravenous immunoglobulin. Five patients lost their grafts at a mean of 200 +/- 270 days. The overall incidence of C4d deposition was 14%; it was seen both in the early and late posttransplantation period. Although a diffuse staining pattern was more frequently seen in the early period, C4d deposition indicated a poor allograft prognosis in both periods. Introduction of C4d staining into the routine may guide more specific treatments directed toward the humoral alloresponse.     

Peritubular capillary deposition of C4d complement fragment in ABO-incompatible renal transplantation with humoral rejection

In ABO-incompatible renal transplantation complement activation may be related to antibody-associated humoral rejection. However, immune deposits within the vasculature have been infrequently demonstrated in biopsy specimens. Whether deposition of complement fragment C4d is correlated with graft outcome and pathological findings (as measured by the severity of antibody-associated humoral rejection) is investigated in this study. Nineteen ABO-incompatible and 9 ABO-compatible renal graft biopsy specimens were selected. Four out of 19 ABO-incompatible patients lost their grafts within 1 yr. Ten out of 19 ABO-incompatible and just 1 out of 9 ABO-compatible patients, had prominent C4d deposition in peritubular capillaries. ABO-incompatible patients with predominant C4d deposition showed few tubulitis, accumulation of polymorphonuclear cells and thrombosis in peritubular and glomerular capillaries. The severity of the humoral rejection was correlated to C4d deposition in peritubular capillaries. Three out of four graft losses in ABO-incompatible renal transplantation showed severe humoral rejection and profuse deposition of C4d complement fragments in peritubular capillaries. Immunosuppression therapy was discontinued in the 4th patient, who lost his graft because of his lethal intestinal bleeding. C4d deposition in peritubular capillaries would be helpful for differential diagnosis between humoral rejection and drug-induced nephrotoxicity, and may serve as a sensitive marker of ABO-incompatible humoral rejection for patients with unsatisfactory (no glomeruli) biopsy specimens.     

Humoral immune responses in the pathogenesis of bronchiolitis obliterans syndrome after lung transplantation

Lung transplantation is recognized as a viable treatment option in a variety of end-stage pulmonary diseases. However, the long-term survival is limited by the development of bronchiolitis obliterans syndrome (BOS). Bronchiolitis obliterans syndrome occurs in more than half of lung transplant recipients who survive more than 5 years and is the leading cause of death in the late posttransplantation period. The specific etiology and pathogenesis of BOS are not well understood. The current premise is that BOS represents a common lesion in which different inflammatory insults such as ischemia-reperfusion, rejection, and infection can lead to a similar histological and clinical outcome. However, the observation that early development of BOS is predicted by the frequency and severity of acute rejection episodes indicates that alloimmune-dependent mechanisms play a crucial role in the pathogenesis of BOS. The evidence presented in this review will demonstrate that BOS is the result of indolent humoral immune responses developed against major histocompatibility complex molecules expressed by airway epithelial cells of the lung allograft. Currently, treatment of BOS is rarely successful. Therefore, a better understanding of the immunopathogenesis of BOS is of paramount importance toward improving long-term graft function and patient survival after lung transplantation.     

Renal allograft C4d deposition in Chinese: Hong Kong perspective

Background: Acute rejection constitutes a significant proportion of renal allograft loss. Peritubular capillary deposition of C4d has been recognized as the footprint of humoral alloimmunity and proven to be a sensitive and specific marker for humoral rejection in the appropriate clinical context. Its presence in indication biopsies is the most important independent risk factor for graft failure. Data are, however, scarce among Chinese subjects. Methods: We retrospectively reviewed all renal graft biopsies performed from 1 April 2002 to 31 March 2006 for unexplained acute renal dysfunction or delayed graft function. Renal outcomes were assessed at the time of renal biopsy and at 1 month, 3 months, 6 months and 1 year afterwards. Survival was assessed by Kaplan–Meier analysis. Multivariate analysis was used to determine if C4d positivity is an independent risk factor for poor renal outcome. Results: Fifty‐two biopsies were included, of which 16 were positive for peritubular capillary C4d. Peritubular capillary C4d was associated with lower glomerular filtration rate and higher serum creatinine at 6 and 12 months after renal biopsies. The C4d‐positive group fares worse in terms of death‐censored graft failure, doubling of serum creatinine and reaching 50% of glomerular filtration rate at the end of the study. Peritubular capillary C4d deposition was the only significant risk factor that predicts graft failure in multivariate analysis. Conclusion: Our findings confirmed the independent prognostic value of peritubular capillary C4d staining on renal allograft survival in Chinese.     

C4d—The Witness of Humoral Rejection

Objective

Acute antibody-mediated (humoral) rejection is a major cause of morbidity, graft loss, and mortality among heart transplant patients. Herein we have presented our experience using C4d to characterize humoral rejection.

Materials and Methods

All nonformalin-fixed cardiac graft biopsies (protocol or emergency) received between May 2007 and May 2008 were examined by immunofluorescence for C4d.

Results

One hundred twelve endomyocardial biopsies from 25 transplanted patients included 20 males and 5 females of ages ranging from 3 to 71 years. The number of biopsies per subject varied from 1 to 11; the timespan between transplantation and the diagnostic biopsies ranged from days to 8 years. Thirteen biopsies showed acute humoral rejection (intramyocardial capillaries positive for C4d); 31, acute cellular rejection (grades 1R, 2R); 7, both humoral and cellular rejection; and 1, acute humoral rejection and allograft vasculopathy. Some of the positive biopsies belonged to the same person, and some to transplanted individuals with signs and symptoms suggestive of rejection, while others did not. The persistence of humoral rejection, despite the disappearance of a cellular component, correlated with slower clinicoechocardiographic improvement.

Conclusions

C4d positivity is a morphologic sign of humoral rejection. It may hasten the appearance and/or worsening of allograft vasculopathy independent of patient age or posttransplantation time.     

Therapy with plasmapheresis and intravenous immunoglobulin for acute humoral rejection in kidney transplantation

BACKGROUND: Acute humoral rejection (AHR) is characterized by acute graft dysfunction associated with de novo production of donor-specific alloantibodies (DSA) and C4d deposition in peritubular capillaries of the renal allograft. It has been reported the combination of plasmapheresis (PP) and intravenous gamma globulin (IVIG) as effective rescue therapy for established AHR. METHODS: Between 1999 and 2004, seven kidney allografts recipients suffered from AHR diagnosed by severe rejection and C4d staining in peritubular capillaries. All patients had a negative cross-match before renal transplantation. RESULTS: All patients were treated with daily sessions of PP and in four cases IVIG was added after the last PP session. Tacrolimus and mycophenolate mofetil were employed as maintenance immunosuppressive regimen. In one case, rituximab was added to PP and IVIG owing to refractory humoral rejection. At 1 year, patient survival was 100%, allograft survival was 70%, and the mean serum creatinine was 201 micromol/L. CONCLUSIONS: AHR is a severe form of rejection associated with a poor prognosis, but its early diagnosis and treatment with PP and IVIG allows reversal of AHR reaching a 70% graft survival at 1 year.     

Clinical impact of complement deposition findings on biopsies in acute rejection episodes of pediatric renal transplant patients

IntroductionRejection is the most important problem for renal graft function and survival. Complement system plays a key role in immune responses from host to graft. It was demonstrated that complement system activation is related with renal fibrosis. We evaluate clinical impact of complement deposition findings on biopsies in acute rejection episodes of pediatric renal transplant patients.MethodDemographics of the patients, graft functions, acute rejection episodes and graft loss were recorded from data files of 165 pediatric renal transplant patients. Findings of 98 renal biopsies were retrospectively evaluated.ResultsThirty three patients with kidney transplant had 44 acute rejection episodes (32 pure cellular acute rejection episodes / 1 pure humoral acute rejection episode / 11 combined acute cellular and acute humoral rejection episodes) proven by biopsy. C1q staining was positive in 7 biopsies, C3 staining in 15 biopsies and, C4d staining in 15 biopsies. 26 patients had graft fibrosis. All patients with a rejection history had a significant decrease in GFR value during follow-up. Patients who did not have fibrotic changes in first biopsy had same level of deterioration of GFR when compared with patients who had fibrotic changes in first biopsy.ConclusionWe could not demonstrate a significant relation between complement deposition and renal fibrosis, and between complement deposition and GFR values. Our data demonstrated that graft outcomes and graft loss after acute rejection episodes cannot be predicted only with complement deposition on graft or only with graft fibrosis.     

C3D deposition in peritubular capillaries indicates a variant of acute renal allograft rejection characterized by a worse clinical outcome

BACKGROUND: C4d deposition in peritubular capillaries (PTCs) is a sign of humoral renal allograft rejection and an independent predictor of graft survival. Few investigators have focused on the meaning of capillary C3 deposition in rejecting grafts. Because C3 production can result from both classic and alternative pathway activation of the complement cascade, it is not clear whether C3 deposition indicates a distinct entity of acute rejection (AR) or merely represents a separate form of C4d-positive AR. METHODS: We examined the deposition of C3d in the PTCs of recipients with AR in the first year posttransplantation (n=30). Clinical outcome variables and histology were compared with C3d-negative control patients (n=82). RESULTS: C3d-positive patients demonstrated more frequent preexisting T-cell antibodies (57%) and more re-transplants (37%), and they received more blood transfusions (mean 10.3 units). C3d-positive patients experienced more frequent multiple AR episodes (57%) and delayed graft function (36.7%). All nine C3d-positive recipients screened for posttransplantation donor-specific human leukocyte antigen antibodies demonstrated positive results. Graft failure occurred in 23% of C3d-positive recipients (7.3% in the control group) (P=0.03). C3d-positive biopsies showed significantly less tubulitis (P=0.03), whereas congestive PTCs with intraluminal accumulation of polymorphonuclear leukocytes were conspicuous. Thrombi, fibrinoid necrosis, and acute tubular necrosis were not more pronounced. In 19% of rejection biopsies, C3d deposition in PTCs was present without C4d deposition. In the remaining biopsies, C3d and C4d deposition was found simultaneously. CONCLUSIONS: The deposition of complement factor C3d in PTCs indicates a variant type of AR characterized by a worse clinical outcome.     

C4d deposition in acute rejection: an independent long-term prognostic factor.

Peritubular capillary deposition of C4d has been demonstrated to be associated with both acute humoral and vascular rejection and increased graft loss. Whether it is an independent predictor of long-term graft survival rates is uncertain. The biopsies (n = 126) from all patients (n = 93) with a tissue diagnosis of acute rejection that were performed between July 1, 1995, and December 31, 1997, were classified according to Cooperative Clinical Trials in Transplantation (CCTT) criteria. Fresh frozen tissue was immunostained for C4d. There were 58 patients with CCTT type I (interstitial) rejection and 35 with CCTT type II (vascular) rejection. For 34 patients, at least one biopsy exhibited peritubular C4d deposition (C4d+ group). The C4d+ group had proportionately more female patients (P = 0.003), more patients with high (>30%) panel-reactive antibody levels (P = 0.024), more patients with resistance to conventional antirejection therapy (P = 0.010), and fewer patients with postrejection hypertension (P = 0.021) and exhibited a greater rate of graft loss (38 versus 7%, P = 0.001). Peritubular C4d deposition was associated with significantly lower graft survival rates in the CCTT type I rejection group (P = 0.003) and the CCTT type II rejection group (P = 0.003). Multivariate analyses demonstrated that peritubular C4d deposition (P = 0.0002), donor age (P = 0.0002), cold ischemic time (P = 0.0211), and HLA matches (P = 0.0460) were significant independent determinants of graft survival rates. Peritubular C4d deposition is a significant predictor of graft survival rates and is independent of histologic rejection type and a variety of clinical prognostic factors.