key term - Antigens

Definition

Antigens are molecules, usually proteins or polysaccharides, that are recognized by the immune system as foreign or different from the body's own cells. They trigger an immune response, leading to the production of antibodies and the activation of other immune defenses to neutralize or eliminate the perceived threat.

5 Must Know Facts For Your Next Test

1. Antigens can be derived from pathogens, such as bacteria, viruses, and parasites, as well as from the body's own cells in the case of autoimmune diseases.
2. The adaptive immune system, including B cells and T cells, is responsible for recognizing and responding to specific antigens.
3. Antigen presentation by MHC molecules on the surface of cells is a crucial step in the activation of T cell-mediated immune responses.
4. The diversity of the antibody repertoire allows the immune system to recognize a vast array of potential antigens.
5. Vaccines work by exposing the immune system to specific antigens, triggering the production of memory cells that can mount a rapid response upon future exposure.

Review Questions

• Explain the role of antigens in the context of the immune system's response to pathogens.
  • Antigens play a central role in the immune system's defense against pathogens. When the body encounters a foreign antigen, such as a bacterial or viral protein, the adaptive immune system recognizes it as a threat and mounts a specific response. This involves the activation of B cells, which produce antibodies that bind to the antigen, and T cells, which can directly attack cells displaying the foreign antigen. The recognition of antigens is a crucial step in the adaptive immune response, allowing the body to identify and eliminate invading pathogens.
• Describe how the presentation of antigens by MHC molecules is involved in the activation of T cell-mediated immunity.
  • The major histocompatibility complex (MHC) plays a vital role in the presentation of antigens to T cells, which is a crucial step in the activation of T cell-mediated immunity. MHC molecules on the surface of cells bind to and display fragments of antigens, including those derived from pathogens. T cells, through their T cell receptors, can then recognize these MHC-bound antigen fragments and become activated. This antigen presentation by MHC molecules is essential for the initiation of T cell responses, such as the activation of cytotoxic T cells to directly kill infected cells or the stimulation of helper T cells to coordinate the broader immune response.
• Evaluate the role of antigens in the development and use of vaccines for the prevention of infectious diseases.
  • Vaccines are a crucial tool in the prevention of infectious diseases, and they work by exposing the immune system to specific antigens. By introducing either weakened or inactivated forms of a pathogen's antigens, vaccines trigger the production of memory B and T cells that can quickly recognize and respond to the actual pathogen upon future exposure. This primes the immune system, allowing for a rapid and effective response that can prevent or significantly reduce the severity of the disease. The ability of vaccines to elicit an immune response against specific antigens is central to their success in protecting individuals and populations from a wide range of infectious diseases. Ongoing research and development of new vaccines continue to leverage our understanding of antigen recognition and the immune system's response to these foreign molecules.

Related terms

Antibodies: Proteins produced by B lymphocytes that bind to specific antigens, neutralizing them or marking them for destruction by other immune cells.

Epitope: The specific region of an antigen that is recognized and bound by an antibody or T cell receptor.

Major Histocompatibility Complex (MHC):

A group of genes that encode proteins involved in the presentation of antigens to T cells, allowing the immune system to distinguish self from non-self.