Class I human antigens, also known as human leukocyte antigens (HLA) class I antigens, are cell-surface proteins found on the majority of human nucleated cells. These antigens play a crucial role in the immune system by presenting antigens to T cells, which are specialized immune cells responsible for identifying and destroying foreign substances or infected cells.
The class I human antigens are encoded by a group of genes called the major histocompatibility complex (MHC) class I genes, which are located on chromosome 6. Each individual inherits a unique set of HLA class I alleles from their parents.
The class I antigens consist of a glycoprotein complex made up of a heavy chain, known as HLA-A, -B, or -C, and a molecule called β2-microglobulin. These chains are responsible for binding short peptide fragments derived from inside the cell, which are then presented on the cell surface for recognition by T cells. This allows the immune system to differentiate between self and non-self cells or identify infected cells.
The presence of class I human antigens is essential for effective immune responses, as they enable T cells to recognize and eliminate foreign invaders, such as bacteria, viruses, or cancer cells. Additionally, their genetic diversity plays a crucial role in transplantation medicine, as matching HLA class I antigens between donor and recipient reduces the risk of rejection.
In conclusion, class I human antigens are cell-surface proteins that facilitate immune responses by presenting antigens to T cells. They are encoded by genes within the major histocompatibility complex and play a vital role in immune surveillance and transplantation compatibility.
