From HLA typing to anti-HLA antibody detection and beyond: The road ahead.

The complex polymorphism of the HLA genes and the need of a proper identification of anti-HLA antibodies have led to continuously develop novel practical and feasible technologies in the field of organ and tissue transplantation. Technologies to identify HLA molecules have evolved from the serological to the molecular methods and a true innovation in the DNA sequencing has taken place with the development of next generation sequencing. An interesting field to explore is how the information resulting from the HLA-DNA sequencing can be applied in the clinical setting by including the alloimmunization assessment. Indeed, a good characterization of anti-HLA antibody at epitope level can reduce the risk of immunization. Many anti-HLA antibodies are specific for epitopes rather than for HLA antigens and the knowledge of unacceptable epitopes allows to reduce the number of mismatched antigens. Furthermore, high resolution HLA allele typing could help to understand the epitopes against which antibodies are developed. However, the improvements should not only concern the diagnostic tools in the pre-transplantation phase, but also the monitoring of post transplantation outcome. There is a growing interest in developing new non-invasive biomarkers to monitor the rejection. Currently, increasing evidence has focused on miRNAs, epigenetic markers emerged as regulators of molecular events that are differently expressed in biopsies and blood as well as in urinary samples of transplanted recipients. The implementation of next generation sequencing and genome-wide expression analysis together with functional assays may provide useful tools to evaluate the epigenetic modulation in transplantation biology but many efforts are requested for translating in the clinical arena the results obtained in experimental models.