"antigen"的定义和意义

What is an "antigen"?

An antigen is a foreign substance that triggers an immune response in the human body. It can be a molecule, such as a protein or a carbohydrate, that is recognized as non-self by the immune system. Antigens are often found on the surface of pathogens, such as bacteria or viruses, but can also be present on allergens or cells from transplanted organs. When the immune system encounters an antigen, it initiates an immune response to eliminate or neutralize it. This response involves the production of antibodies, activation of immune cells, and the development of immune memory. Antigens are crucial for the body's ability to distinguish between self and non-self and play a vital role in immune defense and disease recognition.