Class I antigens refer to a group of proteins found on the surface of most cells in the human body. These antigens are part of the major histocompatibility complex (MHC) system, which plays a crucial role in the immune response as it helps the immune system distinguish between self and non-self cells.
The class I antigens, also known as MHC class I molecules, are encoded by a group of genes located on chromosome 6 in humans. These proteins act as markers on the surface of cells, allowing the immune system to recognize and respond to any foreign substances, such as viruses or bacteria, that may have invaded the body.
The primary function of class I antigens is to present peptide fragments derived from both self and non-self proteins to cytotoxic T cells, a type of white blood cell. This process, known as antigen presentation, helps activate the T cells and direct them to destroy infected or abnormal cells, thereby defending the body against pathogens or cancerous cells.
Class I antigens are highly polymorphic, meaning they exist in multiple different forms within a population. This genetic diversity allows the immune system to recognize a wide range of foreign substances. However, the polymorphic nature of class I antigens also poses challenges in organ transplantation, as mismatched antigens can trigger rejection responses.
In summary, class I antigens are proteins found on the surface of most cells in the body that play a critical role in the immune response by presenting foreign or abnormal proteins to cytotoxic T cells for recognition and destruction.
