IgG

Definition

IgG, or Immunoglobulin G, is the most abundant type of antibody found in the blood and extracellular fluid, playing a critical role in the body's immune response. It is known for its ability to neutralize pathogens such as bacteria and viruses, marking them for destruction by other immune cells. IgG also has a unique ability to cross the placenta, providing passive immunity to the fetus and newborn.

5 Must Know Facts For Your Next Test

1. IgG accounts for approximately 75-80% of all antibodies in the serum and is crucial for long-term immunity.
2. There are four subclasses of IgG (IgG1, IgG2, IgG3, and IgG4), each with slightly different functions and properties.
3. IgG can opsonize pathogens, meaning it coats them to enhance their recognition and destruction by phagocytic cells.
4. In response to infections, levels of IgG rise significantly, and it can remain elevated long after the infection has cleared, providing ongoing protection.
5. IgG's ability to cross the placenta is vital for protecting newborns from infections during their first few months of life.

Review Questions

• How does IgG contribute to the adaptive immune response following an infection?
  • IgG plays a pivotal role in the adaptive immune response by specifically targeting and neutralizing pathogens after exposure. When a person is infected, B cells produce IgG antibodies that bind to antigens on the pathogens, facilitating their opsonization and marking them for destruction by other immune cells. This targeted approach not only helps clear the infection but also establishes immunological memory, ensuring a faster and more robust response if the same pathogen is encountered again.
• Discuss how the structure of IgG facilitates its function in immune defense mechanisms.
  • The structure of IgG is designed to enhance its functionality in immune defense. It consists of two heavy chains and two light chains forming a Y-shaped molecule with variable regions that allow it to bind specifically to antigens. The constant region of IgG enables it to interact with other components of the immune system, such as complement proteins and Fc receptors on phagocytes, promoting opsonization and enhancing phagocytosis. This dual capability underscores why IgG is so effective in neutralizing pathogens and coordinating a comprehensive immune response.
• Evaluate the implications of altered IgG levels in autoimmune disorders and how this might affect treatment strategies.
  • Altered levels of IgG can significantly impact autoimmune disorders, where the immune system mistakenly targets self-antigens. In such cases, elevated IgG levels may indicate a heightened immune response against body tissues, complicating disease management. Treatment strategies may need to focus on modulating the immune system to reduce excessive IgG production while still providing adequate protection against infections. Understanding these dynamics helps clinicians personalize therapies that balance immune suppression with maintaining protective immunity.

Related terms

Antibody: A protein produced by the immune system that recognizes and binds to specific antigens, helping to neutralize or eliminate pathogens.

Immunization: The process by which an individual's immune system becomes fortified against an agent, often through vaccination, leading to the production of antibodies like IgG.

Autoimmunity: A condition in which the immune system mistakenly attacks its own body’s cells, often involving inappropriate responses from antibodies such as IgG.