IgG

Definition

IgG, or Immunoglobulin G, is a type of antibody that plays a crucial role in the immune system by identifying and neutralizing pathogens like bacteria and viruses. It is the most abundant antibody in the bloodstream, accounting for about 75-80% of all immunoglobulins. IgG is key in both the humoral immunity response and in providing long-term protection against infections due to its ability to remember past encounters with specific pathogens.

5 Must Know Facts For Your Next Test

1. IgG is divided into four subclasses: IgG1, IgG2, IgG3, and IgG4, each having different functions and properties related to immune response.
2. IgG can cross the placenta, providing passive immunity to the fetus during pregnancy, which protects newborns from infections in their early months.
3. IgG is known for its ability to opsonize pathogens, marking them for destruction by other immune cells like phagocytes.
4. In response to an infection, IgG levels rise significantly within days to weeks, making it an important indicator in diagnosing various diseases.
5. IgG can remain in the body for a long time after an infection has cleared, which allows for quicker responses upon subsequent exposure to the same pathogen.

Review Questions

• How does IgG contribute to the body's ability to respond to previously encountered pathogens?
  • IgG contributes to the immune response by providing long-term memory against specific pathogens. Once the body has been exposed to a pathogen, B cells produce IgG antibodies that remain in circulation. If the same pathogen is encountered again, these memory IgG antibodies facilitate a faster and more effective immune response, neutralizing the pathogen before it can cause illness.
• Discuss the role of IgG in both humoral immunity and passive immunity during pregnancy.
  • In humoral immunity, IgG is essential as it helps to identify and neutralize extracellular pathogens through mechanisms like opsonization and neutralization. Additionally, during pregnancy, IgG plays a vital role in passive immunity by crossing the placenta from mother to fetus. This transfer provides newborns with immediate protection against infections until their own immune systems mature and can produce antibodies.
• Evaluate the importance of measuring IgG levels in clinical settings for diagnosing infections or immune disorders.
  • Measuring IgG levels is critical in clinical settings as it provides insights into an individual's immune status and history of infections. Elevated IgG levels may indicate recent or chronic infections, while low levels might suggest an underlying immunodeficiency. Additionally, specific IgG subclass measurements can help differentiate between types of immune responses or diagnose particular immune disorders, making it an essential tool for healthcare professionals.

Related terms

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

B Cells: A type of white blood cell that produces antibodies, including IgG, as part of the adaptive immune response.

Humoral Immunity: The aspect of immunity that is mediated by antibodies produced by B cells, which circulate in body fluids and target extracellular pathogens.