Leukozytenantigens

Leukozytenantigens, often abbreviated as HLA (Human Leukocyte Antigens), are proteins found on the surface of white blood cells and other nucleated cells in the human body. These antigens play a crucial role in the immune system, particularly in distinguishing between the body's own cells and foreign invaders. HLA molecules are highly polymorphic, meaning there are many different versions of these genes within the human population. This genetic diversity is essential for the immune system's ability to recognize a wide range of pathogens.

The HLA system is divided into two main classes: Class I and Class II. HLA Class I molecules are found on almost all nucleated cells and present peptides derived from intracellular proteins to cytotoxic T cells. HLA Class II molecules are primarily found on antigen-presenting cells, such as macrophages, dendritic cells, and B cells, and present peptides from extracellular proteins to helper T cells. This interaction between HLA molecules and T cells is fundamental to the adaptive immune response, enabling the body to mount a targeted defense against infections and other threats.

Due to their role in immune recognition, HLA antigens are also critical in transplantation. The compatibility of HLA types between a donor and recipient significantly influences the success of organ and tissue grafts. Mismatched HLA antigens can trigger an immune response, leading to rejection of the transplanted material. Genetic testing for HLA compatibility is therefore a standard procedure in organ transplantation. Furthermore, certain HLA types are associated with an increased susceptibility to specific autoimmune diseases, suggesting a link between HLA genes and the development of conditions where the immune system mistakenly attacks the body's own tissues.