Carbohydrate antigens are specific carbohydrate molecules that can trigger an immune response in the body. These antigens are often found on the surface of cells and can be recognized by antibodies, which are proteins produced by the immune system. Carbohydrate antigens play a crucial role in various biological processes, including cell recognition and signaling. These antigens are important in medical contexts, such as blood typing and organ transplantation. For example, the ABO blood group system is determined by the presence of specific carbohydrate antigens on red blood cells. Understanding carbohydrate antigens helps in diagnosing diseases and developing vaccines.