HLAkompleks

The HLAkompleks, commonly known as the human leukocyte antigen (HLA) complex, is a region on the short arm of chromosome 6 that plays a crucial role in the immune system. It is one of the most gene-dense regions in the human genome and contains over 200 genes, though only a small fraction are directly involved in immune function. The HLA complex is essential for distinguishing between the body’s own cells and foreign invaders, such as viruses, bacteria, and other pathogens.

The primary function of the HLA complex is mediated by its class I and class II molecules, which present antigens to immune cells. Class I molecules are found on nearly all nucleated cells and display peptides derived from intracellular pathogens to cytotoxic T cells, triggering an immune response. Class II molecules, expressed mainly on antigen-presenting cells like dendritic cells, macrophages, and B cells, present extracellular antigens to helper T cells, coordinating adaptive immunity.

Genetic variation within the HLA complex is extensive, with high levels of polymorphism that contribute to individual differences in immune responses. This diversity is advantageous for population-level resistance to infectious diseases but can also lead to complications in organ transplantation, as mismatched HLA types between donor and recipient increase the risk of rejection. HLA typing is therefore a critical step in determining tissue compatibility for transplants.

Beyond immunity, the HLA complex has been linked to susceptibility or resistance to various autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, and multiple sclerosis. Additionally, certain HLA alleles are associated with increased or decreased risk for conditions like HIV progression and certain cancers. Research into the HLA complex continues to expand our understanding of immune regulation and its broader implications in health and disease.