[Diagnosis and management of renal allograft rejection]

Renal allograft rejection involves many mechanisms of innate and adaptive immunity, responsible for parenchymal inflammatory lesions that negatively impact the long-term outcomes of the renal allograft. The heterogeneous presentations of rejections in terms of clinical, biological and histological aspects make them difficult to manage in daily clinical practice. Indeed, current therapeutic strategies are disappointing in term of long-term outcomes, including graft survival. In this article, we will discuss the main effector mechanisms of rejection and their histological classification, as well as the existing treatments and those currently under evaluation.

[18F]FDG PET/CT imaging disproves renal allograft acute rejection in kidney transplant recipients with acute kidney dysfunction: a validation cohort

PURPOSE

[¹⁸F]FDG PET/CT may predict the absence of acute allograft rejection (AR) in kidney transplant recipients (KTRs) with acute kidney injury (AKI). Still, the proposed threshold of 1.6 of the mean of mean standardized uptake values (mSUVmean) in the renal parenchyma needs validation.

METHODS

We prospectively performed 86 [¹⁸F]FDG PET/CT in 79 adult KTRs who underwent per-cause transplant biopsy for suspected AR. Biopsy-proven polyoma BK nephropathies (n = 7) were excluded. PET/CT was performed 192 ± 18 min after administration of 254.4 ± 30.4 MBq of [¹⁸F]FDG. The SUV_mean was measured in both upper and lower poles of the renal allograft. One-way analysis of variance (ANOVA) and Tukey's studentized range test were sequentially performed. The receiver operating characteristic (ROC) curve was drawn to discriminate "AR" from non-pathological ("normal" + "borderline") conditions.

RESULTS

The median age of the cohort was 55 [43; 63] years, with M/F gender ratio of 47/39. The mean eGFR was 31.9 ± 14.6 ml/min/1.73m². Biopsies were categorized in 4 groups: "normal" (n = 54), "borderline" (n = 9), "AR" (n = 14), or "others" (n = 2). The median [min; max] mSUV_mean reached 1.72 [1.02; 2.07], 1.97 [1.55; 2.11], 2.13 [1.65, 3.12], and 1.84 [1.57; 2.12] in "normal," "borderline," "AR," and "others" groups, respectively. ANOVA demonstrated a significant difference of mSUV_mean among groups (F = 13.25, p < 0.0001). The ROC area under the curve was 0.86. Test sensitivity and specificity corresponding to the threshold value of 1.6 were 100% and 30%, respectively.

CONCLUSION

[¹⁸F]FDG PET/CT may help noninvasively prevent inessential transplant biopsies in KTR with AKI.

Fluorodeoxyglucose F(18) Positron Emission Tomography Coupled With Computed Tomography in Suspected Acute Renal Allograft Rejection

Management of kidney transplant recipients (KTRs) with suspected acute rejection (AR) ultimately relies on kidney biopsy; however, noninvasive tests predicting nonrejection would help avoid unnecessary biopsy. AR involves recruitment of leukocytes avid for fluorodeoxyglucose F(18) ((18) F-FDG), thus (18) F-FDG positron emission tomography (PET) coupled with computed tomography (CT) may noninvasively distinguish nonrejection from AR. From January 2013 to February 2015, we prospectively performed 32 (18) F-FDG PET/CT scans in 31 adult KTRs with suspected AR who underwent transplant biopsy. Biopsies were categorized into four groups: normal (n = 8), borderline (n = 10), AR (n = 8), or other (n = 6, including 3 with polyoma BK nephropathy). Estimated GFR was comparable in all groups. PET/CT was performed 201 ± 18 minutes after administration of 3.2 ± 0.2 MBq/kg of (18) F-FDG, before any immunosuppression change. Mean standard uptake values (SUVs) of both upper and lower renal poles were measured. Mean SUVs reached 1.5 ± 0.2, 1.6 ± 0.3, 2.9 ± 0.8, and 2.2 ± 1.2 for the normal, borderline, AR, and other groups, respectively. One-way analysis of variance demonstrated a significant difference of mean SUVs among groups. A positive correlation between mean SUV and acute composite Banff score was found, with r(2)  = 0.49. The area under the receiver operating characteristic curve was 0.93, with 100% sensitivity and 50% specificity using a mean SUV threshold of 1.6. In conclusion, (18) F-FDG PET/CT may help noninvasively prevent avoidable transplant biopsies in KTRs with suspected AR.

Contribution of donors after cardiac death to the deceased donor pool: 2002 to 2009 University of Liege experience

OBJECTIVE

In this study, we have evaluated the organ procurement and transplantation activity from donors after cardiac death (DCD) at our institution over an 8-year period. Our aim was to determine whether this program influenced transplantation programs, or donation after brain death (DBD) activity.

METHODS

We prospectively collected our procurement and transplantation statistics in a database for retrospective review.

RESULTS

We observed an increasing trend in potential and actual DCD number. The mean conversion rate turning potential into effective donors was 58.1%. DCD accounted for 16.6% of the deceased donor (DD) pool over 8 years. The mean age for effective DCD donors was 53.9 years (range, 3-79). Among the effective donors, 63.3% (n = 31) came from the transplant center and 36.7% (n = 18) were referred from collaborative hospitals. All donors were Maastricht III category. The number of kidney and liver transplants using DCD sources tended to increase. DCD kidney transplants represented 10.8% of the DD kidney pool and DCD liver transplants made up 13.9% of the DD liver pool over 8 years. The DBD program activity increased in the same time period. In 2009, 17 DCD and 33 DBD procurements were performed in a region with a little >1 million inhabitants.

CONCLUSION

The establishment of a DCD program in our institution enlarged the donor pool and did not compromise the development of the DBD program. In our experience, DCD are a valuable source for abdominal organ transplantation.

[Monoclonal antibodies in renal transplantation]

Renal transplantation is the best treatment for end-stage renal disease, but requires efficient immunosuppressive therapy. The latter has evolved over recent years with the development of more powerful drugs and of monoclonal antibodies with very specific target. The first monoclonal antibodies, acting against the interleukin 2 receptor, named basiliximab and daclizumab, have showed an excellent tolerance profile and efficacy to reduce acute graft rejection. However, in spite of these properties, the development of delayed graft function or the graft and patient survivals at 1 year were not modified by the use of such specific treatment. One potential advantage could yet be a decreasing need for corticosteroids and sometimes calcineurin inhibitors which could provide some long term benefits for the renal graft, but also the patient. Alemtuzumab, another monoclonal antibody, aimed at the membrane glycoprotein CD52, can also decrease the incidence of acute rejection and the depth of the required immunosuppressive therapy. Other antibodies are still in development with some interesting preliminary results which however demand confirmation in larger studies.

[Polyomavirus BK infection in renal transplant recipients]

Beside acute rejection or immunosuppressive therapy toxicity, infection by Polyomavirus BK, usually not aggressive in immunoactive patients, has emerged as an important factor affecting graft function in renal transplant recipients. Indeed, one of the most important complications of BK infection is nephropathy. Viral replication in the urinary tract as assessed by the presence of "decoy cells", or by a positive PCR for BK virus has been detected in up to half of the recipients but only 5% will present nephropathy which is usually the only sign. The most common risk factors for this emerging new cause are new immunosuppressive drugs and rejection episodes. The gold standard to diagnose BK nephropathy is immunohistochemical staining for large T antigen in graft biopsy specimens. Urine cytology examination and DNA BK PCR are used as a screening test. The prognosis in BK nephropathy has been considered to be poor. The early reduction of immunosuppression can improve the prognosis and perhaps also cidofovir or leflunomide use.

[Pancreas transplantation in the management of diabetes]

Pancreas transplantation has now become an established option in the treatment of diabetic complications. It normalizes glucose metabolism, prevents, stabilizes and improves the evolution of diabetes-associated lesions. Improvements in surgical procedure and in immunosuppression have better defined its indications. Combined kidney-pancreas transplantation appears today as the best treatment for the diabetic patient with end stage renal disease. Isolated pancreas transplantation is reserved to non-uremic patients with severe diabetic complications or with hyperlabile glycaemic control and severe impairment of quality of life.

Protein kinase- and staurosporine-dependent induction of neurite outgrowth and plasminogen activator activity in PC12 cells

We analysed how interactions between protein kinase-dependent intracellular signalling pathways were implicated in the control of the production of tissue-type plasminogen activator (tPA) and the generation of neurite outgrowth by PC12 cells. To that aim, cells were treated with agents that interact with the trk receptor and with protein kinases A and C. Nerve growth factor induced only the formation of large neurites. The release of the protease and the production of short neurite outgrowth were found to be protein-kinase-A-dependent events that could be enhanced by simultaneous activation of protein kinase C with phorbol ester. At high concentration, staurosporine, a nonselective inhibitor of protein kinases, induced the production of short neurites and mimicked the protein-kinase-A-dependent effect on tPA release. Such a response was not observed with K-252a, an analogue of staurosporine devoid of neurite-outgrowth-promoting activity. The responses to protein kinase A stimulation and the addition of staurosporine, although similar, seemed to occur through an activation of distinct, yet interacting, signalling pathways. In conclusion, tPA release and large neurite outgrowth from PC12 cells are controlled by parallel, albeit interacting, pathways, suggesting that these two potentially antagonistic events in PC12 cell differentiation can be modulated in a concerted way or independently of each other, depending on the activity of several protein kinases.