HLAtype

HLAtype refers to the designation of an individual's human leukocyte antigen profile, determined by testing for alleles at the HLA gene complex. Commonly reported loci include HLA-A, HLA-B, HLA-C (Class I) and HLA-DRB1, HLA-DQB1, HLA-DPB1 (Class II). A typical HLAtype lists specific alleles, for example HLA-A*02:01, HLA-B*13:02, HLA-DRB1*04:01. HLAtype is used to describe immunological compatibility and is central to transplantation and disease research.

Biology: HLA genes reside in the major histocompatibility complex on chromosome 6 and encode cell-surface proteins that present peptide antigens to T cells. The region is highly polymorphic and exhibits strong linkage disequilibrium, yielding many distinct HLAtypes across populations and over time.

Typing methods: Serological methods were historically used, but modern HLAtype relies on molecular techniques. PCR-based sequence-specific oligonucleotide probes (SSO), sequence-based typing (SBT), and next-generation sequencing (NGS) provide high-resolution allele calls. Nomenclature uses a four-digit allele family with suffixes like HLA-A*02:01; higher resolution may show additional fields. Resolution depends on the testing method and clinical purpose.

Applications: In transplantation, HLAtype matching reduces graft rejection and graft-versus-host disease. In hematopoietic stem cell transplantation, donor-recipient matching is critical. HLAtype also informs pharmacogenomics, such as HLA-B*57:01 associated with abacavir hypersensitivity and HLA-B*15:02 risk for carbamazepine-induced reactions in some populations. Associations between specific alleles and autoimmune diseases are also studied, though results vary by ethnicity.

Limitations and considerations: Despite high resolution, perfect matches are not always possible; typing errors, ambiguities, and evolving allele catalogs can complicate interpretation. Privacy and consent concerns accompany HLA data, given its potential link to disease risk and ancestry.