Tissue typing for kidney transplantation for the general nephrologist

Immunosuppression of HLA identical living-donor kidney transplant recipients: A systematic review

BACKGROUND

Kidney transplant (KT) recipients of HLA identical siblings (HLAid) have lower immunological risk, but there are no specific recommendations for immunosuppression. Our aim was to analyze evidence about results from HLAid living-donor recipients under different immunosuppression in the current era of immunological risk assessment.

METHODS

Systematic review of studies describing associations between outcomes of HLAid living-donor KT recipients according to their immunological risk and applied immunosuppression.

RESULTS

From 1351 studies, 16 (5636 KT recipients) were included in the analysis. All studies were retrospective, ten comparing immunosuppression strategies, and six immunological risk strata. Of those ten, six studies were published in 1990 or earlier and only three included tacrolimus. The evidence is poor, and the inclusion of calcineurin inhibitors does not demonstrate better results. Furthermore, only few studies describe different immunosuppression regimens according to the patient immunological risk and, in general, they do not include the assessment with new solid phase assays.

CONCLUSIONS

There are no studies analyzing the association of outcomes of HLAid KT recipients with current immunological risk tools. In the absence of evidence, no decision or proposal of immunosuppression adapted to modern immunological risk assessment can be made currently by the Descartes Working Group.

Approaches for the characterization of clinically relevant pre-transplant human leucocyte antigen (HLA) antibodies in solid organ transplant patients

The avoidance of antibody-mediated rejection (AMR) attributed to human leucocyte antigen (HLA) antibody incompatibility remains an essential function of clinical Histocompatibility and Immunogenetics (H&I) laboratories who are supporting solid organ transplantation. Developments in HLA antibody identification assays over the past thirty years have greatly reduced unexpected positive cellular crossmatches and improved solid organ transplant outcomes. For sensitized patients, the decision to register unacceptable HLA antigen mismatches is often heavily influenced by results from solid phase antibody assays, particularly the Luminex^® Single Antigen Bead (SAB) assays, although the clinical relevance of antibodies identified solely by these assays remains unclear. As such, the identification of non-clinically relevant antibodies may proportionally increase the number of unacceptable transplant mismatches registered, with an associated increase in waiting time for a compatible organ. We reflect on the clinical relevance of antibodies identified solely by the Luminex SAB^® assays and consider whether the application of additional assays and/or tools could further develop our ability to define the clinical relevance of antibodies identified in patient sera. Improvements in this area would assist equity of access to a compatible transplant for highly sensitized patients awaiting a solid organ transplant.

The changing landscape of HLA typing: Understanding how and when HLA typing data can be used with confidence from bench to bedside

Human leukocyte antigen (HLA) genes are extraordinary for their extreme diversity and widespread impact on human health and disease. More than 30,000 HLA alleles have been officially named and more alleles continue to be discovered at a rapid pace. HLA typing systems which have been developed to detect HLA diversity have advanced rapidly and are revolutionizing our understanding of HLA's clinical importance. However, continuous improvements in knowledge and technology have created challenges for clinicians and scientists. This review explains how differences in HLA typing systems can impact the HLA types that are assigned. The consequences of differences in laboratory testing methods and reference databases are described. The challenges of using HLA types that are not equivalent are illustrated. A fundamental understanding of the continual expansion of our understanding of HLA diversity and limitations in some of the typing data is essential for using typing data appropriately in clinical and research settings.