Compatibility and kidney transplantation: the way to go

Human leukocyte antigen distributions do not share a copula across sub-populations

The distribution of human leukocyte antigens in the population assists in matching solid organ donors and recipients when the typing methods used do not provide sufficiently precise information. This is made possible by linkage disequilibrium (LD), where alleles co-occur more often than random chance would suggest. There is a trade-off between the high bias and low variance of a broad sample from the population and the low bias but high variance of a focused sample. Some of this trade-off could be alleviated if sub-populations shared LD despite having different allele frequencies. These experiments show that Bayesian estimation can balance bias and variance by tuning the effective sample size of the reference panel, but the LD as represented by an additive or multiplicative copula is not shared.

Impact of HLA polymorphisms among cadaveric donors on kidney graft allocation

This study provides data on HLA-A, -B, and -DRB1 frequencies among 861 end-stage renal disease (ESRD) patients from Croatia and estimates the benefit of the kidney exchange program by comparing HLA distribution and assessing HLA mismatches (MMs) within a group of ESRD patients who received kidney grafts from 707 cadaveric donors (422 from Croatia and 285 from Eurotransplant). Patients positive for HLA-B*07, -B*08, or -B*44 genes more often received a kidney from ET donors, while HLA-DRB1*11 and -DRB1*16 positive patients more frequently received a kidney from CRO donors. ABDR MM 000 was more frequently present in the case of transplantation from ET donors, while MM 222 was significantly more frequent when the donor was from Croatia. Sensitized patients received kidney more frequently from ET donors (P < .0001). A large pool of organ donors with different HLA gene distributions allows for a higher probability of transplantation from HLA highly matched donor.

Should physicians tell the truth without taking social complications into account? A striking case

The principle of respect for autonomy requires informing patients adequately and appropriately about diagnoses, treatments, and prognoses. However, some clinical cases may cause ethical dilemmas regarding telling the truth. Under the existence especially of certain cultural, social, and religious circumstances, disclosing all the relevant information to all pertinent parties might create harmful effects. Even though the virtue of telling the truth is unquestionable, sometimes de facto conditions compel physicians to act paternalistically to protect the patient/patients from imminent dangers. This article, which aims to study the issue of whether a physician should always tell the truth, analyzes an interesting case that represents the detection of misattributed paternity during pre-transplant tests for a kidney transplant from the son to the father in Turkey, where social, cultural, and religious factors have considerable impact on marital infidelity. After analyzing the concept of telling the truth and its relationship with paternalism and two major ethical theories, consequentialism and deontology, it is concluded that the value of the integrity of life and survival overrides the value of telling the truth. For this reason, in the case of a high possibility of severe and imminent threats, withholding some information is ethically justifiable.

[Determination of HLA-A, -B and -DRB1 polymorphism in brain dead organ donors representative of the Colombian general population, 2007-2014]

INTRODUCTION

Genes encoding for human leukocyte antigens (HLA) are highly polymorphic and of great importance in organ transplantation procedures, as determining allelic frequencies in defined populations is taken into account among the scientific criteria for organ allocation.

OBJECTIVE

The objective of this study was to establish the antigen HLA-A, -B, and -DRB1 haplotype frequencies in organ donors representative of the Colombian population after brain death.

MATERIALS AND METHODS

We conducted a descriptive retrospective study involving 2,506 cadaveric organ donors including an allelic and haplotype analysis of HLA-A, -B and -DRB1; we also determined the Hardy-Weinberg equilibrium.

RESULTS

We identified 21, 43 and 15 allelic loci for groups A*, B* and DRB1*, respectively. We detected 1,268 HLA-A, -B and -DR, 409 HLA-A-B, 383 HLA-DR-B, and 218 HLA-A-DR haplotypes. The three loci were found to be in Hardy-Weinberg equilibrium between the number of heterozygotes observed and the expected number, with p values of ;0.05.

CONCLUSIONS

This study provides information on the allelic distribution of HLA class I and II in organ donors from the six regions in which Colombia is structurally divided to provide transplant services.

Patient and graft outcome in current era of immunosuppression: a single centre pilot study

OBJECTIVES

The present single centre study aims at analyzing the impact on renal allograft outcome of the important changes which occurred in the transplant population and immunosuppressive therapy during the last two decades.

METHODS

From 2000 to 2013, 779 single kidney transplantations were performed on 635 patients who all received on an intent-to-treat basis steroids, a calcineurin inhibitor, mycophenolate mofetil and an induction therapy with either antithymocyte globulin or an antagonist directed to the interleukin (IL)-2 receptor. Uni- and multivariate analyses of patient and immunologic graft survival were conducted.

RESULTS

The sole factor predicting patient survival is recipient's age: 10-year survival rates are 94·7, 81·6 and 57·9% for the <45, 45-60 and >60 years age groups, respectively (P<0·001). Peak (>50% panel reactive antibodies) anti-human leucocyte antigens (HLA) sensitization, cold ischaemia time and HLA-B and -DR mismatches (MM) influence graft outcome: at 10 years, the difference in 10-year survival rates is 5·9% between grafts from sensitized and not sensitized patients (90·9 vs 96·8%, P = 0·002), 3·8% between grafts with <18 and ≧18 hours cold ischaemia (96·6 vs 92·8%, P = 0·003), 7·3% between grafts with no MM and either B or DR MM versus those with B and DR MM (96·8 vs 89·5%, P = 0·002).

CONCLUSION

In our single centre experience, graft survival was most strongly determined by HLA matching, offering excellent long term graft outcome to most patients.

Matching for Human Leukocyte Antigens (HLA) in corneal transplantation - to do or not to do

As many patients with severe corneal disease are not even considered as candidates for a human graft due to their high risk of rejection, it is essential to find ways to reduce the chance of rejection. One of the options is proper matching of the cornea donor and recipient for the Human Leukocyte Antigens (HLA), a subject of much debate. Currently, patients receiving their first corneal allograft are hardly ever matched for HLA and even patients undergoing a regraft usually do not receive an HLA-matched graft. While anterior and posterior lamellar grafts are not immune to rejection, they are usually performed in low risk, non-vascularized cases. These are the cases in which the immune privilege due to the avascular status and active immune inhibition is still intact. Once broken due to infection, sensitization or trauma, rejection will occur. There is enough data to show that when proper DNA-based typing techniques are being used, even low risk perforating corneal transplantations benefit from matching for HLA Class I, and high risk cases from HLA Class I and probably Class II matching. Combining HLA class I and class II matching, or using the HLAMatchmaker could further improve the effect of HLA matching. However, new techniques could be applied to reduce the chance of rejection. Options are the local or systemic use of biologics, or gene therapy, aiming at preventing or suppressing immune responses. The goal of all these approaches should be to prevent a first rejection, as secondary grafts are usually at higher risk of complications including rejections than first grafts.

Human leukocyte antigens and alloimmunization in heart transplantation: an open debate

Considerable advances in heart transplantation outcome have been achieved through the improvement of donor-recipient selection, better organ preservation, lower rates of perioperative mortality and the use of innovative immunosuppressive protocols. Nevertheless, long-term survival is still influenced by late complications. We support the introduction of HLA matching as an additional criterion in the heart allocation. Indeed, allosensitization is an important factor affecting heart transplantation and the presence of anti-HLA antibodies causes an increased risk of antibody-mediated rejection and graft failure. On the other hand, the rate of heart-immunized patients awaiting transplantation is steadily increasing due to the limited availability of organs and an increased use of ventricular assist devices. Significant benefits may result from virtual crossmatch approach that prevents transplantation in the presence of unacceptable donor antigens. A combination of both virtual crossmatch and a tailored desensitization therapy could be a good compromise for a favorable outcome in highly sensitized patients. Here, we discuss the unresolved issue on the clinical immunology of heart transplantation.