HLAalleelit

HLAalleelit are the variants of the human leukocyte antigen (HLA) genes that encode the cell-surface proteins responsible for presenting peptide fragments to T cells. The HLA gene region, located on chromosome 6, is among the most polymorphic in the human genome, producing thousands of alleles that shape individual immune profiles. HLAalleelit are categorized into class I and class II genes. HLA class I genes (HLA-A, -B, -C) generate molecules that present endogenous peptides to CD8+ T cells, while HLA class II genes (HLA-DR, -DQ, -DP) produce molecules that present exogenous peptides to CD4+ T cells. This broad diversity underpins tissue compatibility, influences infection susceptibility, autoimmunity risk, and responses to vaccines and therapies.

In transplantation and bone marrow procedures, matching donor and recipient HLAalleelit improves graft survival and reduces rejection risk. Allele frequencies vary by ancestry, producing population-specific haplotypes and linkage patterns that are important for donor registries and clinical planning. Molecular typing methods, including sequence-based typing and PCR-based approaches, are used to identify HLAalleelit at high resolution; serological testing remains useful for common antigens in some settings.

Most disease associations with HLAalleelit are probabilistic rather than deterministic. Certain alleles are linked to autoimmune conditions—for example, HLA-B27 with ankylosing spondylitis; HLA-DQ2 and HLA-DQ8 with celiac disease; HLA-DRB1*04 with rheumatoid arthritis. Pharmacogenomic associations also exist, such as HLA-B*57:01 and abacavir hypersensitivity. Ongoing research in HLAalleelit enhances understanding of antigen presentation, with implications for transplantation, infectious disease susceptibility, autoimmunity, and personalized medicine.