C4D Deposition and Positive Posttransplant Crossmatch Are Not Necessarily Markers of Antibody-Mediated Rejection in Renal Allograft Recipients

Endothelin A Receptors Expressed in Glomeruli of Renal Transplant Patients May Be Associated with Antibody-Mediated Rejection

BACKGROUND

Non-human leukocyte antigen (HLA) anti-endothelin A receptor antibodies are presented as being potentially important, but the expression of the endothelin A receptor in glomeruli (ETA receptor (g+)) has not yet been described. We decided to evaluate the presence and relevance of the ETA receptor in for-cause renal transplant biopsies. The aim of our study was to evaluate the immunoreactivity of the ETA receptor and its significance in patients who underwent a renal transplant biopsy due to the deterioration of transplant function, with detailed characterization of staining in glomeruli.

METHODS

The immunohistochemical expression of ETA receptor (ETAR) was analyzed in renal transplant biopsies. Microscopic evaluation was performed on paraffin sections in glomeruli. The analysis was performed using a two-step scale (0: lack of ETAR expression; 1: the presence of ETAR expression-mild to moderate immunoreactivity).

RESULTS

We analyzed 149 patients who underwent renal allograft biopsy after renal transplantation. Positive staining of ETA receptors in glomeruli (ETA receptor (g+)) was noticed in 13/149 (8.7%) patients. Five of these 13 (38.5%) patients with ETA receptor (g+) developed antibody-mediated rejection (AMR), while 13 of the remaining 136 (9.5%) ETA receptor (g-) patients developed AMR (p = 0.0022). Graft loss was noticed in all but one ETA receptor (g+) patient with AMR (4/5; 80%), but only in 2/13 (15%) ETA receptor (g-) patients with AMR (p = 0.009) during the first year after biopsy.

CONCLUSIONS

The expression of endothelin A receptors in glomeruli seems to be a potentially important feature in the diagnosis of damage during antibody-mediated rejection. It may help to identify patients at a higher risk of allograft rejection and injury.

Endothelin A Receptors Expressed in Renal Blood Vessels of Renal Transplant Patients Are Connected With Acute Tubular Necrosis or Antibody-Mediated Rejection

BACKGROUND

The role of non-HLA antibodies named antiendothelin A receptor antibodies is potentially significant but not established. The significance of the endothelin A receptor (ETAR) and its expression in renal biopsy has not been defined. We decided to evaluate the presence and relevance of ETARs in renal transplant biopsy for cause. The aim of our study was to evaluate the immunoreactivity of the ETAR and its significance in patients who had a renal transplant biopsy due to deterioration of transplant function (biopsy for cause) with detailed characterization of staining in small and intermediate arteries of renal transplant biopsies.

METHODS

Immunohistochemical expression of ETARs was analyzed in 162 renal transplant biopsies. Microscopic evaluation of ETAR expression (polyclonal antibody) was performed on paraffin sections. ETAR expression was analyzed in renal blood vessels (small and intermediate arteries) based on three-step scale.

RESULTS

We analyzed 154 patients who had renal allograft biopsy between 6 days and 24 years (median 597 days) after transplantation. Positive staining of ETAR in small and intermediate arteries was noticed in 9 patients. Among these patients, 4 had early biopsies (<3 months after transplantation), all developed acute tubular necrosis, and 1 developed additionally acute humoral rejection. Further, 4 patients had late biopsy (1-8 years after transplantation) and all developed characteristics of antibody mediated rejection. Lastly, 1 patient had no characteristic changes in the biopsy 4 months after transplantation. Graft loss 1 year after biopsy was higher in patients who were ETAR-positive but statistical significance was not achieved.

CONCLUSIONS

The expression of endothelin receptors in renal blood vessels (small and intermediate arteries) seems to be important in diagnosis of damage during acute tubular necrosis and antibody-mediated rejection.

A significant role for anti-human leukocyte antigen antibodies and antibody-mediated rejection in the biopsy-for-cause population

The role of anti-human leukocyte antigen (HLA) antibodies and antibody-mediated rejection is well known, but our comprehension and the preventive measures we take seem to be insufficient. One of the major causes of premature renal transplant loss is recepients' immunologic hyperactivity to donors' antigens. Monitoring of humoral alloreactivity gives hope for early diagnosis and adequate therapy. The goal of our analysis was the assessment of the influence of anti-HLA antibodies on the function and survival of transplants. In our study we included 60 consecutive renal transplant recipients who had a renal transplant biopsy-for-cause performed due to insufficiency. Transplant biopsies were performed between the 7th day and 12th year (median, 2 years) after transplantation. Anti-HLA antibodies were present in 20 patients (33%). The patients were divided into 2 groups according the presence of anti-HLA antibodies. In a 12-month observation, 10/20 (50%) patients in the anti-HLA(+) group returned to dialysis in contrast with 7/40 (17.5%; P = .014) in the anti-HLA(-) group. Also, 8/10 (80%) of the anti-HLA(+) patients who lost the transplant had anti-HLA Abs class II and only 2/10 (20%) had anti-HLA Abs class I. Anti-HLA antibodies were specific to a donor (donor-specific antibodies [DSA]) in 8/10 (80%) of the patients who lost the transplant. Anti-HLA antibodies appeared de novo in 50% of patients who lost the transplant. Nonadherence was suspected in 50% of patients. Acute humoral rejection occurred in 1 patient. Also, 8/10 (90%) developed chronic active humoral rejection. Our study revealed that graft loss in the renal transplant biopsy-for-cause population with the presence of anti-HLA Abs during a 12-month observation reached 50%. Nonadherence in these patients was very high and amounted to 50%. Monitoring of renal transplant recipients and individualization of therapy considering humoral activity should prolong renal graft survival.

Positive C4d in kidney transplantation biopsy: clinical impact

BACKGROUND

Deposition of C4d in peritubular capillaries of renal graft is normally associated with the presence of antibody-mediated rejection. The clinical impact of its presence in patients with renal transplant in Colombia is uncertain, as well as the association in acute rejection and the response to the management and survival of the graft. The aim of this study was to determine the risk of having positive C4d in biopsies of patients with episodes of acute cellular rejection.

METHODS

We retrospectively reviewed 226 biopsies of kidney transplantation, all of them with acute rejection and histopathological findings classified according to Banff criteria 2009 and performed between January 2005 and December 2012 for graft dysfunction. C4d staining was performed by immunohistochemistry.

RESULTS

C4d staining was positive in 25 of 226 biopsies. Rejection time in patients with positive C4d was 15 months in average vs 8 months with negative C4d.

CONCLUSIONS

With the use of a multivariate analysis, we found that the unique risk for C4d in our population was the positive panel reactive antibodies and elapsed time between transplant and the rejection (odds ratio: 2.12, P = .034) and that the other variables analyzed are not related to the expression of C4d.

The impact of de novo donor-specific anti-human leukocyte antigen antibodies on 5-year renal transplant outcome

Numerous studies have shown that circulating donor-specific antibodies targeting human leukocyte antigen (HLA) are associated with accelerated renal transplant failure, but many patients with these antibodies have good graft function. The aim of our study was to investigate the long-term graft function and survival in patients with de novo post-transplant donor-specific anti-HLA antibodies (DSA). Our prospective study included 78 consecutive recipients with a negative crossmatch before transplantation. Recipient serum samples were assayed for DSA in week 2 and 1, 3, 6, 9, 12 months after transplantation using a complement-dependent lymphocytotoxic technique with donor lymphocytes. Additionally, patients with DSA and stable renal function in the first year were tested with a more sensitive flow-panel-reactive antibody. DSA were present in 34 (44%) of our patients during the first 12 months after transplantation. Biopsy-proved acute rejection occurred in 11 DSA-positive and 10 DSA-negative patients. Seven DSA-positive patients had antibody-mediated rejection and no DSA-negative ones developed humoral rejection. The serum creatinine level in DSA-positive patients was significantly higher (2.48 vs 1.43 mg/dL) in year 5. The 13 (38%) DSA-positive patients with good graft function in month 12 were stable during a 5-year follow-up: their serum creatinine was 1.46 ± 0.4 in year 1 and 1.56 ± 0.4 mg/dL in year 5 and nobody lost their allograft. One- and 5- year graft survivals were appropriately 85% and 59% in DSA-positive patients compared to 93% and 93% in DSA-negative patients. To sum up, post-transplant DSA had a significant influence on kidney function and graft survival but in 38% of patients the presence of DSA did not decrease a 5-year renal function. A good renal allograft function in the presence of DSA in the first year after transplantation and cessation of their production in the subsequent years may be a good prognostic marker for a long-term allograft function and survival.

Long-term follow-up of non-HLA and anti-HLA antibodies: incidence and importance in renal transplantation

BACKGROUND

Detection of antibody-mediated injury is becoming increasingly important in post-transplant patient care. The role of donor-specific anti-human leukocyte antigen (HLA) antibodies in kidney transplant damage is known, whereas the significance of non-HLA antibodies remains an unresolved concern. The aim of the study was to determine the presence and influence on renal function of non-HLA and anti-HLA antibodies in stable patients at 5 years after kidney transplantation.

METHODS

We evaluated the antibodies in 35 consecutive patients with stable renal function at 5 years after transplantation.

RESULTS

Pretransplant screening for donor-specific antibodies by CDC cross-matches was negative in all patients. Anti-endothelial cell antibodies (AECA), anti-angiotensin II type 1 receptor antibodies (anti-AT1R), and anti-endothelin receptor antibodies (anti-ETAR) were assayed as non-HLA antibodies. Non-HLA antibodies were observed in 12 (34%) patients, including AECA (n = 5; 14%), anti- AT1R (n = 6; 17%), anti-ETAR (n = 4; 11%), and both anti-AT1R and anti-ETAR (n = 3). Among 13 (37%) patients with anti-HLA antibodies, 7 also had both non-HLA antibodies: AECA (n = 1), anti-AT1R (n = 3), and anti-ETAR (n = 3). The antibody-negative group (n = 13) showed significantly better renal function than the antibody-positive group (non-HLA and/or anti-HLA; n = 22). Biopsy-proven acute rejection had occurred in 2 of 13 (15%) antibody-negative versus 8 of 22 (36%) antibody-positive patients. These preliminary data revealed an high prevalence of autoantibody and alloantibody production among stable patients at 5 years after kidney transplantation.

CONCLUSION

Simultaneous production of these antibodies and their association with reduced renal function suggests that active humoral immune responses are poorly controlled by immunosuppression.

Optimal cutoff point for immunoperoxidase detection of C4d in the renal allograft: results from a multicenter study

BACKGROUND

Although C4d deposition in peritubular capillaries has been identified as a strong risk factor for subsequent renal allograft loss, the optimal cutoff for the fraction of peritubular capillaries needed to establish a positive stain in formalin-fixed, paraffin-embedded material has not been defined systematically. The objective of this study was to establish the threshold for positive staining that best predicts renal outcome in renal biopsies in a multicenter study in which local and central pathologic conditions were compared.

METHODS

Unstained renal biopsy slides were obtained from 296 patients. The percentage of peritubular capillaries staining positively for C4d was detected by immunoperoxidase staining.

RESULTS

The percentage C4d deposition ranged from 0% to 90% with 44% (129/296) having a positive percentage of C4d staining. The median for positive cases was 25%. Local C4d+ results were reported qualitatively, with 28% recorded as positive for C4d. Using a centrally determined cutoff of 10%, tests for agreement of local and central C4d staining were fair (κ 0.40, 95% confidence interval 0.29-0.51). Raising the centrally determined cutoff to 25% or 50% did not change the κ values (0.44 and 0.41, respectively). By Cox proportional hazards model, C4d positivity (centrally determined assessment) using a cutoff of 10% was the strongest predictor of time to graft loss (hazard ratio 2.66, 95% confidence interval 1.68-4.21). Centrally determined C4d positivity correlated with Banff scores indicative of acute inflammation but not with scores indicative of fibrosis/atrophy or transplant glomerulopathy.

CONCLUSIONS

Our findings indicate that C4d positivity, defined as more than or equal to 10% by immunoperoxidase, is a strong predictor of graft loss.

Quilty effect areas are frequently associated with endocardial C4d deposition

BACKGROUND

The meaning and clinical implications of the Quilty effect (QE) are not entirely clear. In some biopsies we have found complement split C4d deposition in QE areas, but we do fully comprehend the frequency or pathogenic relationships involved. The objective of this study was to gain insight into the immunologic events involved in the QE, and to understand if and how it relates to complement activation.

METHODS

Protocol allograft biopsies (January to December 2005) with evidence of the QE, without cellular rejection or changes suspicious for antibody-mediated rejection, were selected for C4d, CD3, CD20 and CD68 immunohistochemistry.

RESULTS

Among 128 allograft biopsies (42 patients), 17 (11 patients) fulfilled the inclusion criteria. Eleven of the 17 biopsies (64.7%), from 8 patients, showed C4d deposition in the endocardium; the positivity was interestingly linear in the endocardium and surrounded by the lymphocytes forming the Quilty lesion. In some cases, the linear C4d deposition extended to the endocardium surrounding the QE area. This pattern was not detected in any of 66 heart allograft biopsies without the QE. B cells were second to T cells in their contribution to the QE, comprising a median of 40% (range, 20% to 50%) of the cells. C4d deposition was not associated with clinical alterations.

CONCLUSIONS

The QE is frequently associated with C4d deposition in the endocardium of patients without evidence of rejection. This event suggests a pathogenic relationship between the QE and complement activation. It is possible that the simultaneous presence of both features in an allograft heart biopsy, without evidence of rejection, indicates better adaptation of allograft to host ("accommodation"); however, the precise meaning and implications are not yet known.