tissuetyping

Tissuetyping, or tissue typing, is the assessment of immunogenetic compatibility between a donor and a recipient to guide transplantation and histocompatibility decisions. The focus is on human leukocyte antigens (HLA), which are highly variable cell-surface proteins that influence immune recognition. Matching HLA antigens between donor and recipient can reduce the risk of graft rejection and graft-versus-host disease, improving transplant outcomes.

Modern tissue typing uses a range of methods. Serology and flow cytometry were early approaches that detect surface antigens but offer limited resolution. DNA-based typing, including PCR-based methods and sequence-based typing, provides high-resolution determination of HLA alleles. Next-generation sequencing (NGS) and other advanced techniques further refine allele typing, enabling precise matching at key HLA loci such as HLA-A, -B, -C, -DRB1, and -DQB1.

Applications of tissuetyping include solid organ transplantation (e.g., kidney, liver, heart) where ABO compatibility and HLA matching influence graft survival, though the urgency of transplantation and immunosuppression strategies also play major roles. In hematopoietic stem cell or bone marrow transplantation, very close HLA matching is critical to reduce severe complications and improve engraftment success. Tissue typing also informs donor selection, allocation in registries, and pre-transplant risk assessment.

Process-wise, samples are collected from donor and recipient and sent to specialized laboratories for typing and crossmatching. Crossmatching tests, including complement-dependent cytotoxicity and flow cytometry crossmatches, assess whether recipient antibodies would react with donor tissue. Virtual crossmatching uses sensitization data and HLA databases to predict compatibility when physical testing is limited.

Limitations include incomplete correlation with clinical outcome and the evolving understanding of non-HLA factors. Ongoing developments aim to improve resolution, speed, and predictive accuracy through enhanced sequencing, databases, and integrated matching algorithms.