C4d Deposition In Peritubular Capillaries Research Articles

C4d Deposition Is Associated With Chronic Allograft Nephropathy in Rats and Could Be Influenced by Immunosuppressants

Aims Deposition of C4d in peritubular capillaries (PTC) has been considered to be a marker of humoral immunity in renal transplant. This study is to investigate C4d deposition in rat renal allografts undergoing CAN and the effects of immunosuppressants on it. Methods Fisher 344 rat renal grafts were orthotopically transplanted into Lewis rats following the procedure of Kamada with our modification. All the recipients were given CsA 10 mg/kg −1 · d −1 × 10 d and then divided into 5 groups (each n = 9); (1) Vehicle: vehicle orally, (2) CsA: 6 mg/kg −1 · d −1, (3) RAPA: 0.8 mg/kg −1 · d −1, (4) FK 506: 0.15 mg/kg −1 · d −1, (5) MMF: 20 mg/ kg −1 · d −1. At 4 weeks, 8 weeks, 12 weeks, the rats were sacrificed, renal allografts were harvested and sera were collected. The deposition of C4d was detected by immunofluorescence and analyzed by Integrated Optical Density (IOD). The pathological changes were accessed according to the Banff 97 criteria. Results C4d deposition in PTC was found in all the allografts at 4 weeks, while there was no obvious manifestations of CAN in all the groups; the differences of Banff Score between all groups were not significant ( P > .05). The values of IOD in RAPA and MMF group were lower than those in other 3 groups ( P = .002, .006). The differences between RAPA and MMF, and between other 3 groups were not significant ( P > .05). The intensity of C4d increased along with the progression of CAN, the heaviest C4d deposits in PTC were found at 12 weeks, and meanwhile the severest CAN was found. Comparing with Vehicle group, CsA and FK 506 had no effect on C4d deposition ( P > .05), however, MMF and RAPA obviously decreased the C4d deposition ( P = .000). The intensity of C4d deposition had a significant correlation with the severity of CAN ( r = 0.894, P = .000). Conclusions Our study suggests that the deposition of C4d in allografts appears earlier than pathological changes of CAN and has a correlation with the progression of CAN. MMF and RAPA can attenuate CAN by inhibiting humoral immunity. In contrast, CsA and FK 506 have no effect on humoral immunity.

C4d Deposition Is Correlated With the Level of Antivimentin Antibody in Rat Kidneys Undergoing Chronic Allograft Nephropathy

Aims Antivimentin antibody is often produced as an autoantibody after transplantation. C4d deposition, a marker of humoral immunity during transplantation, is believed to reflect alloantibodies. This study investigated the relationship between C4d deposition and humoral immunity to vimentin among rat kidneys undergoing chronic allograft nephropathy (CAN). Methods Fisher 344 rat renal grafts were orthotopically transplanted into Lewis rats following the procedure of Kamada with our modification. All recipients were administered cyclosporine (CsA) (10 mg/kg −1 · d −1 × 10 d) before being divided into 3 groups of oral treatments: (1) vehicle, (2) CsA (6 mg/kg −1 · d −1), and (3) mycophenolate mofetil (MMF; 20 mg/kg −1 · d −1). At 4, 8 and 12 weeks after transplantation, the rats were killed, the renal allografts harvested, and the sera collected. Serum creatinine (SCr) was measured and pathologic changes assessed according to the Banff 97 criteria. The antivimentin antibody was quantified by enzyme-linked immunosorbent assay. The deposition of C4d detected by immunofluorescence was analyzed by integrated optical density (IOD). Results Antivimentin antibody was observed in sera of all transplanted rats. The level of antivimentin antibody (IgGΔOD) increased gradually during the development of CAN from 4 weeks. Simultaneously, C4d deposition in peritubular capillaries also progressively strengthened. There was a strong positive correlation between the content of antivimentin antibody and C4d deposition ( r = 0.892; P = .000). MMF simultaneously decreased antivimentin antibody formation and C4d deposition. In contrast, CsA had no significant effect. Conclusions We demonstrated the production of antivimentin antibodies and the deposition of C4d during the development of CAN. There was a positive correlation between them. Whether humoral immunity to vimentin contributes to C4d deposition is not clear and further studies are needed to elucidate this issue.

C4d Deposition without Rejection Correlates with Reduced Early Scarring in ABO-Incompatible Renal Allografts

C4d deposition in peritubular capillaries is a specific marker for the presence of antidonor antibodies in renal transplant recipients and is usually associated with antibody-mediated rejection (AMR) in conventional allografts. In ABO-incompatible grafts, however, peritubular capillary C4d is often present on protocol biopsies lacking histologic features of AMR; the significance of C4d in this setting remains unclear. For addressing this, data from 33 patients who received ABO-incompatible renal allografts (after desensitization) were retrospectively reviewed. Protocol biopsies were performed at 1 and/or 3 and 6 mo after transplantation in each recipient and at 12 mo in 28 recipients. Twenty-one patients (group A) had strong, diffuse peritubular capillary C4d staining without histologic evidence of AMR or cellular rejection on their initial protocol biopsies. The remaining 12 patients (group B) had negative or weak, focal peritubular capillary C4d staining. Three grafts (two in group B) were lost but not as a result of AMR. Excluding these three patients, serum creatinine levels were similar in the two groups at 6 and 12 mo after transplantation and at last follow-up; however, recipients in group A developed significantly fewer overall chronic changes, as scored by the sum of Banff chronic indices, than group B during the first year after transplantation. These results suggest that diffuse peritubular capillary C4d deposition without rejection is associated with a lower risk for scarring in ABO-incompatible renal allografts; the generalizability of these results to conventional allografts remains unknown.

Circulating Anti-endothelial Cell Antibodies Are Associated with Poor Outcome in Renal Allograft Recipients with Acute Rejection

Anti-endothelial cell antibody (AECA) can cause hyperacute rejection and immediate graft loss after renal transplantation; however, its prevalence and significance during acute rejection are unknown. Previous studies suggested that AECA may be detected in recipients with acute vascular rejection (AVR). We retrospectively analyzed 653 cadaveric renal transplant recipients; circulating AECA was positive in 13 of 47 cases of AVR; another two cases of hyperacute rejection also had detectable AECA. Twenty-six cases of AVR without circulating AECA were selected as controls. AECA-positive AVR usually occurred within 1 yr after transplantation and mostly was resistant to steroid treatment. Compared with the control group, the AECA-positive group was associated with a significantly lower 1-yr graft survival rate (46.7 versus 80.5%; P = 0.038), and more patients had histologic interstitial plasma cell infiltration (53.8 versus 11.5%; P = 0.005). More patients with AECA-positive AVR experienced another one or more episodes of acute rejection during 1 yr of follow-up (75.0 versus 13.0%; P = 0.003). AECA-positive AVR with C4d deposition in peri-tubular capillaries had the worst outcome in this cohort, and it accounted for 38.5% graft loss in AVR. AECA in turn accounted for 71.4% of graft loss in C4d(+) AVR. Circulating AECA is associated with poor outcome in renal allograft recipients with acute rejection and should be monitored regularly.

Observation of Efficacy and Safety of Converting the Calcineurin Inhibitor to Sirolimus in Renal Transplant Recipients With Chronic Allograft Nephropathy

Objective The objective of this study was to evaluate the efficacy and safety of converting from a calcineurin inhibitor (CNI) to sirolimus among renal transplant recipients with chronic allograft nephropathy (CAN). Methods In 16 patients with CAN, substituted sirolimus for CsA or FK506 and observed the incidence of acute rejection and changes in serum creatinine, triglycerides, cholesterol, blood uric acid, and peripheral blood leukocyte/platelet counts within 12 months. All recipients underwent an allograft biopsy before conversion. The targeted sirolimus level was 4–8 ug/L. Results After conversion to sirolimus, the creatinine level of 7 cases decreased and the efficacy rate was (43.8%). No acute rejection occurred during the follow-up. The cases with hypercholesteremia increased from 3 to 7 after conversion; hypertriglyceridemia increased from 3 to 5; leukopenia occurred in 2; subnormal platelet counts increased from 2 to 3; and hyperuricemia increased from 6 to 7. Meanwhile, the average level of peripheral blood leukocytes obviously decreased in the first month, the average peripheral blood cholesterol increased over 12 months, but the average content of peripheral blood platelets, triglyceride and blood uric acid failed to display as statistic difference. Eight patients showed C4d deposition in peritubular capillary in graft tissue before conversion, 7 cases of whom showed no improvement in renal function. In 6 cases there was no C4d deposition in peritubular capillary in graft tissue. Only 2 of 6 cases showed no improvement in renal function. There were 6 patients whose creatinine level was <2.48 mg/dL before conversion, and renal function in 5 of them improved in a year after conversion. In contrast, among 10 patients whose blood creatinine level was >2.48 mg/dL, only 2 cases improved. Conclusion It is safe for patients with CAN to use substitute sirolimus for CNI; the incidence of acute rejection did not increase. In this study, 43.8% of patients showed improved renal function. The main adverse reactions after conversion to sirolimus were hypercholesteremia and decreased peripheral blood leukocytes. The serum creatinine level and the deposition of C4d in peritubular capillary were important factors influencing therapeutic efficacy.

Anti-glutathione S-transferase T1 antibody-mediated rejection in C4d-positive renal allograft recipients

Chronic humoral rejection is a progressive form of graft injury, with defined diagnostic criteria, the crucial one being the evidence of circulating anti-donor antibodies. These antibodies are mainly directed against human leucocyte antigens (HLA), but other targets have also been described. We previously reported that antibodies against the Glutathione S-transferase T1 (GSTT1) enzyme appear in recipients without the GSTT1 gene who receive a graft from a GSTT1-positive donor. The primary aim of this study was to analyse the role of GSTT1 in cases of antibody-mediated rejection (AMR) in the absence of anti-HLA antibodies. A second objective was to describe the distribution of the GSTT1 enzyme in the human kidney. Four renal biopsies from four renal transplanted patients with declined renal function and circulating anti-donor GSTT1 antibodies were studied for C4d deposits in sections of paraffin-embedded tissue samples. Anti-donor-specific HLA and MICA antibody detection was done with the Luminex platform and anti-GSTT1 antibodies were tested by indirect immunofluorescence on rat tissues and ELISA assay. DNA of the patients was extracted for GSTT1 genotyping. Four patients with the GSTT1 donor/recipient mismatch developed anti-GSTT1 antibodies 32, 42, 48 and 60 months after the transplant. One patient also had donor-specific anti-HLA antibodies. Their biopsies showed pathologic lesions compatible with chronic antibody-mediated rejection (CAMR), along with positive C4d deposition in peritubular capillaries in three of them, being no valuable in the other case. This is the first study reporting an association between the appearance of chronic antibody-mediated renal allograft rejection and the occurrence of de novo production of anti-GSTT1 antibodies, in the absence of anti-HLA donor-specific antibodies. This fact suggests a potential role of the GSTT1 system in anti-graft immune response.

Non-invasive diagnosis of acute rejection in kidney transplants with delayed graft function

Delayed graft function (DGF) often occurs in kidney transplants from deceased donors. We wanted to provide studies giving more accurate non-invasive tests for acute rejection (AR). Using real-time PCR, we examined the expression of cytolytic molecules such as perforin, granzyme B, and fas-ligand along with serpin proteinase inhibitor-9. We also measured the expression of FOXP3, a characteristic gene of T-regulatory cells known to be involved in AR. These studies were conducted on peripheral blood monocytes, urinary cells, and 48 surveillance kidney biopsies taken from a total of 35 patients with DGF. Of these patients, 20 had a histopathological diagnosis of AR, whereas other 28 had characteristics of acute tubular necrosis (ATN). Expression of cytolytic and apoptotic-associated genes in the biopsy tissue, peripheral blood leukocytes, and urinary cells was significantly higher in patients with AR than that in patients with ATN. Diagnostic parameters associated with FOXP3 gene expression were most accurate in peripheral blood leukocytes and urine cells with sensitivity, specificity, positive and negative predictive values, and accuracy between 94 and 100%. Our study shows that quantification of selected genes in peripheral blood leukocytes and urinary cells from renal transplant patients with DGF may provide a useful and accurate non-invasive diagnosis of AR.

Renal allograft C4d deposition in Chinese: Hong Kong perspective

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. 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. 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. Our findings confirmed the independent prognostic value of peritubular capillary C4d staining on renal allograft survival in Chinese.

Peritubular capillary C4d deposition not linked with graft outcome in late acute rejection

Peritubular capillary C4d deposition not linked with graft outcome in late acute rejection

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.

Immunephenotype of Glomerular and Interstitial Infiltrating Cells in Protocol Renal Allograft Biopsies and Histological Diagnosis

Patients with a protocol renal allograft biopsy simultaneously displaying interstitial fibrosis/tubular atrophy (IF/TA) and subclinical rejection (SCR) have a shortened graft survival than patients with a normal biopsy, or with a biopsy only displaying IF/TA or SCR. The poor outcome of these patients could be related with a more severe inflammation. We evaluate the immunophenotype of infiltrating cells in these diagnostic categories. Nonexhausted paraffin blocks from protocol biopsies done during the first year were stained with anti-CD45, CD3, CD20, CD68 and CD15 monoclonal antibodies. Glomerular and interstitial positive cells were counted. C4d deposition in peritubular capillaries was evaluated. Histological diagnoses were: normal (n = 80), SCR (n = 17), IF/TA (n = 42) and IF/TA + SCR (n = 17). Only interstitial CD20 positive cells were significantly increased in patients displaying IF/TA + SCR; normal (137 +/- 117), SCR (202 +/- 145), IF/TA (208 +/- 151) and IF/TA + SCR (307 +/- 180 cells/mm(2)), p < 0.01. The proportion of biopsies displaying C4d deposition was not different among groups. The upper tertile of CD20 positive interstitial cells was associated with a decreased death-censored graft survival (relative risk: 3.01, 95% confidence interval: 1.23-7.35; p = 0.015). These data suggest that B-cell interstitial infiltrates are associated with histological damage and outcome, but do not distinguish whether these infiltrates were the cause or the consequence of chronic tubulo-interstitial damage.

Transplant Glomerulopathy: Ultrastructural Abnormalities Occur Early in Longitudinal Analysis of Protocol Biopsies

Transplant glomerulopathy (TXG) presents a distinctive pattern of glomerular abnormalities. The aim of this study was to describe its sequential ultrastructural pathology. A paired cohort study of 228 protocol biopsies, from our longitudinal database (n = 1345), compared TXG (7 patients, 95 biopsies) and controls (8 patients, 133 biopsies). Ultrastructural morphometry and C4d immunoperoxidase were evaluated from implantation to 5 years after transplantation against sequential histology and functional changes. TXG was predated by early glomerular endothelial cell activation; typified by vacuolation, hypertrophy, serration and expansion of lamina rara interna from 39 +/- 23 days after transplantation. Endothelial cells were transformed into an activated phenotype, containing numerous mitochondria, Golgi and ribosomes. Transition from fenestrated to continuous endothelium, mesangial matrix expansion and podocyte fusion occurred late. Endothelial cell activation also occurred in peritubular capillaries (PTC) followed by basement membrane multi-lamination (p < 0.05-0.001). Light microscopy changes of TXG occurred at 2.3 years. PTC C4d deposition was intermittently expressed over time, correlating with endothelial abnormalities, glomerular C4d and donor-specific antibodies (DSA) (p < 0.05-0.001). In summary, endothelial and subendothelial ultrastructural abnormalities in glomerular and peritubular capillaries are sensitive, early markers of TXG, likely due to stimulation of endothelial cells into an activated phenotype by antibody-mediated sub-lytic complement deposition.

Peritubular capillary C4d deposition in lupus nephritis different from antibody-mediated renal rejection

C4d deposition in peritubular capillaries (PTC) has been used as a marker of antibody-mediated rejection (AMR). However, PTC C4d deposition is not described in patients with lupus nephritis (LN). C4d deposition in PTC was detected in 455 patients with biopsy proven LN in the present study. Renal tissues from 21 cases of acute AMR served as controls. C4d deposition in PTC was found in 31 patients (6.81%) with LN. Patients with PTC C4d positive showed higher SLEDAI score and higher frequency of hypocomplementemia as compared to C4d negative. The prevalence of ANA, anti-dsDNA, anti-Sm and ACA were higher in C4d positive group, and most of these patients showed the diffuse proliferative glomerular lesion. In contrast with acute AMR, the staining pattern of C4d was granular deposition and the detection of C4d along PTC was accompanied by deposition of IgG and C1q or C3. Electron dense deposition on PTC was observed in most of LN patients. In conclusion, C4d deposition in PTC could be found in a small part of patients with LN. Our study suggested for the first time that C4d positive deposition were close relation with the higher disease activity of LN, and that immune complex formation might be involved in PTC C4d deposition in LN patients, Such PTC C4d deposition is distinct from that of AMR.

Peritubular capillary C4d staining in late acute renal allograft rejection - is it relevant?

In the early post-transplant period, renal allograft rejection with diffuse peritubular capillary (PTC) C4d deposition predicts poor graft survival. In the late post-transplant setting, that is, one or more yr after transplantation, the implication of diffuse PTC C4d deposition is still a topic of debate. The purpose of our study was to see if diffuse PTC C4d deposition, in late acute rejection (LAR), occurring more than one yr post-transplant, has any impact on graft survival and function. We selected cases, both cadaveric as well as living donor renal transplant recipients, in whom acute rejection with PTC C4d deposition was first detected after the first year post-transplant. Recipients with multiple acute rejection episodes during the first year post-transplant were excluded from the study. The first biopsy diagnosed with LAR was considered the index biopsy (n = 40). We formed two groups: group 1, C4d-positive LAR (n = 20), and group 2, C4d-negative LAR (n = 20). Groups were matched for maintenance and post-rejection immunosuppressive therapy, baseline serum creatinine levels before the time of the index biopsy, time from transplant to index biopsy, as well as chronic allograft damage index (CADI) score in the index biopsies. We compared the rate of graft loss, and the graft function of the surviving grafts at the end of the study period, as well as histologic parameters in the index biopsy specimens between the two groups. The mean follow-up period was 20 months. No significant differences in the rate of graft loss or graft function were found between groups 1 and 2 at the end of the follow-up period. Histologically, PTC margination and transplant glomerulopathy were more common in the C4d-positive group, and this difference was statistically significant. There was no statistically significant difference in the degree of plasma cell infiltrates. Unlike in the acute setting, the presence or absence of PTC C4d staining in renal allografts with LAR may not have a predictive value regarding graft outcome.

Glomerular Expression of Plasmalemmal Vesicle‐Associated Protein‐1 in Patients with Transplant Glomerulopathy

Transplant glomerulopathy (TG) is a prominent feature of chronic rejection that is characterized by double contours of the glomerular capillaries (GC). In this report, we demonstrate that one of the histopathological features of TG is a phenotypic change of glomerular endothelial cells which is illustrated by increased caveolae formation. To verify the endothelial changes in this disease, we examined the expression of plasmalemmal vesicle-associated protein-1 (PV-1), a glycoprotein associated with plasmalemmal vesicles (caveolae), in the glomeruli of TG patients using pathologische anatomie Leiden-endothelium (PAL-E) antibody. Twenty-six cases of chronic allograft nephropathy (CAN) with TG were examined, compared with 16 cases of CAN without TG, type I MPGN (4 cases), and transplant glomerulitis (8 cases). Overall, 24 of 26 (92.3%), 4 of 16 (25%), 0 of 4, 0 of 8 cases were PAL-E-positive for GC, respectively. Further, the extent of glomerular PAL-E expression was positively correlated with both the grade of TG (rs= 0.72, p = 0.0003) and proteinuria (g/day) (rs= 0.51, p = 0.02). A correlation was not observed between glomerular PAL-E positivity and peritubular capillary C4d deposits (Yetes chi = 0.23, p = 0.89). In summary, the present study demonstrates expression of PV-1 in the GC of TG which is correlated with the grade of TG and proteinuria.

Transplant Glomerulopathy, Late Antibody-Mediated Rejection and the ABCD Tetrad in Kidney Allograft Biopsies for Cause

To define the relative frequency of phenotypes of transplant glomerulopathy, we retrospectively reviewed the findings in 1036 biopsies for clinical indications from 1320 renal transplant patients followed in our clinics between 1997 and 2005. Transplant glomerulopathy, defined by double contours of glomerular basement membranes (D), was diagnosed in 53 biopsies (5.1%) from 41 patients (3.1%) at a median of 5.5 years post-transplant (range 3.8-381 months). In cases with D, we studied the frequency of circulating anti-HLA alloantibody (A), peritubular capillary basement membrane multilayering (B) and peritubular capillary C4d deposition (C). B was present in 48 (91%) of D biopsies. C4d staining by indirect immunofluorescence was detected in 18 of 50 D biopsies studied (36%). By Flow PRA Screening or ELISA, A was detected in 33 (70%) in 47 D cases with available sera, of which 28/33 or 85% were donor-specific. Class II (13/33) or class I and II (17/33) were more common than class I (3/33) antibodies. Thus 73% of transplant glomerulopathy has evidence of alloantibody-mediated injury (A and/or C), with ABCD and ABD being the common phenotypes in biopsies for cause. The remaining 27%, mostly BD, may be a different disease or a stage in which A and C are undetectable.

Histological Markers of Humoral Rejection in Renal Transplant Patients

Diagnosis of “suspicious humoral rejection” can be formulated in the presence of peritubular capillary (PTC) C4d deposition and one of the following tissue changes: (1) acute tubular necrosis, (2) glomerulitis or presence of polymophonuclear leukocytes or monocytes in PTC, or (3) arteritis. From January 2004 to October 2006, we performed immunohistochemical staining with anti-C4d antibody on 54 renal biopsies from 39 renal transplant patients. In 25 biopsies we observed diffuse ( n = 13) or focal ( n = 12) C4d deposition. Based on C4d-positivity, patients were divided into three groups: group 1 included 19 C4d-negative patients; group 2, 10 patients with diffuse C4d-positivity; and group 3, 10 patients with focal C4d-positivity. Panel-reaction antibody–positive tests were associated with diffuse C4d-positivity: 50% of group 2 patients showed a positive test, while no group 1 or 3 patients had a positive test ( P < .001). Glomerulitis was observed in six biopsies and associated with diffuse C4d staining. Graft loss occurred in 3/10 group 2 patients (30%); 2/19 group 1 patients (10.5%), and 1/10 group 3 patients (10%). Viral infections were experienced in the year of the biopsy by 50% of group 1 patients 80% of group 2 patients, and 100% of group 3 patients ( P < .025), indicating a significantly greater number of infections among patients with C4d-positive biopsies. In eight cases, anti-thymocyte globulin was administered less than 21 days before the biopsy: four had diffuse and four had focal C4d positivity.

Subclinical Peritubular Capillaritis at 3 Months Is Associated With Chronic Rejection at 1 Year

Peritubular capillaritis has been associated with chronic rejection, but the characteristics of subclinical lesions in peritubular capillaries are unknown. Fifty-three renal allograft recipients underwent a protocol biopsy at both 3 and 12 months after transplantation. Subclinical chronic antibody-mediated rejection (CAMR) at 1 year was diagnosed when three or more of five criteria were present: basement membrane multilayering of peritubular capillaries (MLPTC), transplant glomerulopathy, increase in intimal fibrosis between 3 and 12 months, C4d deposition in peritubular capillaries, and the presence of anti-human leukocyte antigen antibodies. Six (11.3%) patients met the criteria of CAMR. MLPTC was the most sensitive (83.3%) and specific (89.1%) histological criterion (P=0.0008). Five patients had peritubular capillaritis at their 3-month biopsy. They all developed MLPTC at 1 year (P<0.0001). Three of the patients with early peritubular capillaritis met the criteria of CAMR at 1 year (P=0.0002). Through early detection of subclinical peritubular capillaritis, renal allograft recipients who are at risk for development of MLPTC might be identified. Larger series are needed to confirm these preliminary findings, but this report suggests peritubular capillaritis as an early detection marker for patients at risk for CAMR.

Soluble CD30 in patients with antibody-mediated rejection of the kidney allograft

The aim of our retrospective study was to evaluate the clinical significance of measurement of the soluble CD30 (sCD30) molecule for the prediction of antibody-mediated (humoral) rejection (HR). Sixty-two kidney transplant recipients (thirty-one C4d-positive and thirty-one C4d-negative patients) were included into the study. Soluble CD30 levels were evaluated before transplantation and during periods of graft function deterioration. The median concentrations of the sCD30 molecule were identical in C4d-positive and C4d-negative patients before and after transplantation (65.5 vs. 65.0 and 28.2 vs. 36.0 U/ml, respectively). C4d+ patients who developed DSA de novo had a tendency to have higher sCD30 levels before transplantation (80.7 ± 53.6 U/ml, n = 8) compared with C4d-negative patients (65.0 ± 33.4 U/ml, n = 15). Soluble CD30 levels were evaluated as positive and negative (≥ 100 U/ml and < 100 U/ml respectively) and the sensitivity, specificity and accuracy of sCD30 estimation with regard to finding C4d deposits in peritubular capillaries were determined. The sensitivity of sCD30+ testing was generally below 40%, while the specificity of the test, i.e. the likelihood that if sCD30 testing is negative, C4d deposits would be absent, was 82%. C4d+ patients who developed DSA de novo were evaluated separately; the specificity of sCD30 testing for the incidence of HR in this cohort was 86%. Conclusion We could not confirm in our study that high sCD30 levels (≥ 100 U/ml) might be predictive for the incidence of HR. Negative sCD30 values might be however helpful for identifying patients with a low risk for development of DSA and antibody-mediated rejection.

New treatments for acute humoral rejection of kidney allografts

Acute antibody-mediated rejection (acute humoral rejection; AHR) of organ allografts usually presents as severe dysfunction with a high risk of allograft loss. Peritubular capillary complement C4d deposition with renal dysfunction, associated with circulating donor-specific anti-human leukocyte antigen alloantibodies, is diagnostic of AHR in kidney allografts. Removal of alloantibodies with suppression of antibody production and rejection reversal is now possible. Therapeutic strategies that include combinations of plasmapheresis (or immunoadsorption), tacrolimus, mycophenolate mofetil and/or intravenous immunoglobulins, as well as rituximab or splenectomy, have been recently used to successfully treat AHR. However, the optimal protocol to treat AHR still remains to be defined. Anti-CD20+ monoclonal antibody therapy (rituximab) aiming at depleting B cells and suppressing antibody production has been used as rescue therapy in some episodes of steroid- and antilymphocyte-resistant humoral rejection. Plasmapheresis and/or intravenous polyclonal immunoglobulin, as well as rituximab, have also been used to successfully desensitize selected high-immunological risk patients in anticipation of a previously cross-match positive (or ABO incompatible) kidney transplantation. In the near future, the possible role of new specific anti-B-cell approaches or, possibly, of new anti-T-cell activation approaches using selective agents such as belatacept should be assessed to further refine the present treatment of humoral rejection.