Immunity Quiz

Immunity

• Immunity is the body's ability to resist or eliminate potentially harmful foreign substances or pathogens.
• It involves a complex network of cells, tissues, and organs working together to protect against infection and disease.
• Two main branches of immunity: innate and adaptive immunity.
• Innate immunity is the first line of defense, providing immediate, non-specific responses to a wide range of pathogens.
  • Physical barriers (skin, mucous membranes)
  • Chemical barriers (enzymes, acids)
  • Cellular components (phagocytes, natural killer cells)
• Adaptive immunity is a slower, more specific response that develops after initial exposure to a pathogen.
  • Involves lymphocytes (B cells and T cells)
  • Produces highly specialized antibodies tailored to specific pathogens.
  • Can develop immunological memory, leading to faster and stronger responses upon subsequent encounters with the same pathogen.

Antibody Structures

• Antibodies, also known as immunoglobulins (Ig), are Y-shaped proteins produced by B cells.
• They are crucial components of the adaptive immune system.
• Basic antibody structure consists of:
  • Two identical heavy chains and two identical light chains.
  • The chains are held together by disulfide bonds.
  • Variable regions (Fab) at the tips of the Y. These are specific to a particular antigen.
  • Constant regions (Fc) at the stem of the Y. These determine the antibody's function.
• Different classes of antibodies exist (IgG, IgM, IgA, IgE, IgD), each with unique properties and roles in immune responses.
• IgG is the most abundant antibody in blood, and is involved in various immune functions, including neutralization, opsonization, and complement activation.
• IgM is the first antibody produced during an immune response and is involved in complement activation.
• IgA is primarily found in mucosal secretions and plays a crucial role in preventing pathogen entry.
• IgE is involved in allergic reactions and defense against parasites.
• IgD is primarily found on the surface of B cells, where it acts as an antigen receptor.
• Antigen binding sites on the variable regions of antibodies recognize and bind to specific antigens, which can be found on pathogens, toxins, or other foreign substances.
• The binding of antibodies to antigens can lead to different outcomes, such as neutralization of the pathogen's ability to infect host cells, opsonization (making the pathogen more susceptible to phagocytosis by immune cells), and activation of the complement system (a cascade of proteins that enhance immune function).
• Antibody diversity is generated through a combination of mechanisms, including somatic recombination of gene segments encoding antibody molecules. This mechanism allows for the production of a vast array of antibodies, enabling the immune system to recognize virtually any antigen.
• The constant region of the antibody determines the effector function of the antibody (e.g., complement activation, phagocytosis).