Detection of alloantibody deposition in allografts: capillary C4d deposition as a marker of humoral rejection:

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 diagnostic value of transcription factors T-bet/GATA3 ratio in predicting antibody-mediated rejection

Background. Previous data showed that the predominance of intraglomerular T-bet or GATA3 is correlated with different mechanisms of rejection, suggesting that the ratio of T-bet/GATA3 might be used to distinguish antibody-mediated rejection (ABMR) and T-cell-mediated rejection (TCMR). Methods. We compared the intraglomerular T-bet/GATA3 ratio in ABMR and TCMR. The intragraft expression of T-bet and GATA3 was studied via immunohistochemistry. The correlation of the diagnosis of AMR with the ratio of T-bet/GATA3 was examined. Results. Both intraglomerular T-bet- and GATA3-expressing cells were increased during acute rejection. T-bet/GATA3>1 was strongly correlated with ABMR (93.3% versus 18.2%). The incidence of positive HLA-I/II antibodies and glomerulitis is significantly higher in T-bet/GATA3>1 group (P < 0.001, 0.013, resp.). The scores of peritubular capillary inflammation and glomerulitis were also higher in T-bet/GATA3>1 group (P = 0.052, P < 0.001, resp.). Nevertheless, T-bet/GATA3>1 is also correlated with C4d-negative ABMR and resistance to steroid treatment. Compared with C4d deposition, T-bet/GATA3>1 had a slight lower (90% versus 100%) specificity but a much higher (87.5% versus 68.8%) sensitivity. Conclusion. Our data suggested that intraglomerular predominance of T-bet over GATA3 might be used as diagnosis maker of ABMR in addition to C4d, especially in C4d-negative cases.

Late acute kidney transplant rejection: clinicopathological correlates and response to corticosteroid therapy

Acute rejection is a major cause of kidney allograft dysfunction. It is important to distinguish between cellular and antibody-mediated rejection to guide the treatment strategy. The management of acute antibody-mediated rejection includes aggressive therapy with plasmapheresis and intravenous immunoglobulin. C4d staining of peritubular capillaries has emerged as a valuable tool in identifying antibody-mediated rejection. Late acute rejection has a worse prognosis than early acute rejection. The clinical and pathological features of late acute kidney allograft rejection are not fully understood. We studied the clinicopathological correlates of late acute rejection in our patient population. During an 8-year period, all patients who had late acute rejection (6 months posttransplant) were identified. Patients with severe chronic changes and transplant glomerulopathy were excluded. Patients were divided into C4d+ and C4d- groups [corrected]. Histopathological features and treatment response were evaluated. Nine patients met inclusion criteria (4 C4d+, 5 C4d-). Maintenance therapy consisted of mycophenolate mofetil, calcineurin inhibitors, and low-dose prednisone. All patients received intravenous methlyprednisolone or high-dose oral prednisone as antirejection therapy. Seventy-five percent of patients in the C4d+ group and 80% of patients in the C4d- group had a clinical response to antirejection therapy. The majority of C4d+ patients with late acute rejection who were treated with corticosteroids alone responded to treatment. The study raises the possibility that a subset of C4d+ patients with acute rejection who do not have severe chronic changes might respond to corticosteroid therapy alone.

Late and early C4d-positive acute rejection: Different clinico-histopathological subentities in renal transplantation

This study was performed to investigate the clinical and pathologic features of C4d-positive steroid-resistant acute rejection (AR) at different phases after renal transplantation. Fifty-six kidney allograft recipients with C4d-positive AR were divided into three groups, very early rejection (VER, occurring < or =14 days following transplantation, n=28), early rejection (ER, occurring 15-180 days following transplantation, n=5), and late rejection (LR, occurring >180 days following transplantation, n=23). Clinical and pathological features were evaluated. Significantly more patients in the ER and LR groups were associated with a reduction or withdrawal of immunosuppressants. More patients in the ER and LR groups experienced a significant (>3 g/l) decrease in serum albumin (80% ER, 91.3% LR, 7.1% VER, P<0.001) and a decrease in hemoglobin (>1 g/dl) (80, 100 vs 17.9%, P<0.001). Most VER patients reported a fever and had very rapid graft dysfunction requiring dialysis. Significantly more patients (87%) had interstitial fibrosis and tubular atrophy in the LR group compared with the other groups and 13% had transplant glomerulopathy. Most cases of VER were reversed with tacrolimus and mycophenolate mofetil treatment, with or without immunoadsorption, with a 1-year survival rate of 96.4%, compared with only 60 and 52.2% in the ER and LR groups. In conclusion, C4d-positive steroid-resistant AR at different time points is associated with unique clinico-histopathological manifestations requiring distinct treatment strategies. Late episodes are usually associated with significantly reduced serum albumin and hemoglobin levels and a poorer outcome. A more specialized treatment protocol should be established for these patients.

Tacrolimus combined with mycophenolate mofetil can effectively reverse C4d-positive steroid-resistant acute rejection in Chinese renal allograft recipients

BACKGROUND

Tacrolimus (TAC) combined with mycophenolate mofetil (MMF) has been suggested to play a critical role in the reversal of C4d-positive acute humoral rejection (AHR) in renal transplantation, but the efficacy of using only TAC-MMF without immunoadsorption or plasmapheresis has not been investigated. On the other hand, Chinese recipients of renal grafts usually need lower doses of immunosuppressants, and their optimal treatment for acute humoral rejection has not been established.

METHODS

Since 1999, we have used TAC-MMF to treat steroid-resistant acute rejection (AR). C4d staining was retrospectively performed in 32 patients with steroid-resistant AR, and the treatments of 19 patients with C4d-positive steroid-resistant AR were investigated.

RESULTS

Thirteen of 19 patients received TAC-MMF treatment only; 11 episodes of rejection in them were reversed (7 completely, 4 partially) and only 2 recipients lost their graft. Another 6 patients received immunoadsorption also. One of them failed to respond and lost her graft. Four of 5 patients treated with immunoadsorption and TAC-MMF recovered (3 completely, 1 partially), but 3 of them had severe pneumonia, a complication rate statistically higher than in patients treated with only TAC-MMF (P<0.05). AR occurring during the first two weeks after transplantation had a statistically better outcome than that occurring later (P = 0.003).

CONCLUSION

Our study suggests that the combination of TAC and MMF is a potentially safe and economic treatment for most Chinese renal allograft recipients with C4d-positive steroid-resistant AR, especially for rejections developing within the first two weeks after transplantation.

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.

Late Developing C4d-Positive Humoral Renal Allograft Rejection Associated With Withdrawal of Mycophenolate Mofetil

In renal transplantation, C4d-positive acute humoral rejection (AHR) usually develops in the early stage posttransplantation. It is clear C4d can be detected late after the operation, when it is associated with chronic renal allograft rejection. We report a case of a renal allograft recipient who experienced C4d-positive acute renal allograft rejection associated with withdrawal of mycophenolate mofetil (MMF) at 10 months after transplantation. This 21-year-old single male patient received his first cadaveric renal allograft under immunosuppression with cyclosporine, MMF, and prednisolone. The serum creatinine recovered to the normal range within 4 days. A protocol biopsy performed at 1 month after transplantation revealed no signs of rejection. The graft function was stable until 10 months postoperation, when MMF was converted to mizoribin. Three days later a biopsy showed a C4d-positive rejection. Patient had no response to the MMF combined with tacrolimus and steroid bolus therapy, which generally improves 85% of AHR among Chinese. He finally returned to dialysis. Our report suggested that C4d positive AHR may occur late after transplantation. MMF is important to suppress the body's humoral response to allograft; when MMF was converted to a weaker immunosuppressant, the dose of the other immunosuppressants (cyclosporine for example) must be adjusted properly.

Detectable circulating antiendothelial cell antibodies in renal allograft recipients with C4d-positive acute rejection: a report of three cases

It is suggested that non-HLA endothelial antigens may also cause C4d-positive acute rejection, but this is very rare. We report on three renal allograft recipients who developed C4d-positive acute rejection with detectable circulating antiendothelial cell antibodies (AECAs). All patients had severe dialysis-dependent graft dysfunction. Histologic manifestations include neutrophils infiltration on peritubular capillaries and glomeruli. Endoarteritis can be seen in all the patients. Two patients lost grafts after the rescue therapy including immunoadsorption, mycophenolate mofetil with or without tacrolimus. The titer variation of AECAs might be associated with the graft outcome. In patients those who lost grafts, AECAs titer increased from 1:10 to 1:80 in one patient, and was kept positive during the treatment in the other patient. In the recovered patient, however, the titer became negative from 1:40. From our report, it appears that persisting circulating AECAs during the rescue treatment of C4d-positive acute rejection may be associated with a poor outcome.