Antigén

An antigen is a molecule capable of inducing an immune response in the body, specifically the production of antibodies or the activation of immune cells. These molecules are typically proteins, polysaccharides, nucleic acids, or lipids, and they can originate from pathogens such as bacteria, viruses, fungi, or parasites, as well as from non-infectious substances like toxins, pollen, or transplanted tissues. The immune system recognizes antigens as foreign or harmful, triggering mechanisms to neutralize or eliminate them.

Antigens are detected by immune cells, particularly B cells and T cells, which play key roles in adaptive immunity. B cells produce antibodies that bind specifically to antigens, marking them for destruction by other immune cells. T cells, particularly helper T cells and cytotoxic T cells, recognize antigens presented by other cells, coordinating immune responses or directly attacking infected cells. The specificity of antigen recognition allows the immune system to target particular pathogens while sparing healthy tissues.

Antigens can be classified based on their origin and function. Complete antigens, or immunogens, are large molecules that elicit a full immune response, including antibody production and memory cell formation. Hapten, on the other hand, are small molecules that are not immunogenic on their own but can become antigenic when attached to a carrier protein. Superantigens are a distinct class of antigens that can stimulate a massive and non-specific immune response, often leading to severe symptoms such as fever and shock.

Antigens are also fundamental in medical and research applications. Vaccines contain antigens from pathogens to stimulate protective immunity without causing disease. Diagnostic tests, such as enzyme-linked immunosorbent assays (ELISAs), rely on antigen-antibody interactions to detect infections or autoimmune conditions. Additionally, antigens are used in research to study immune responses and develop therapies for immune-related disorders.