Immune System: IgG and IgA

Overview of Immune System

• The immune system protects the body from pathogens (bacteria, viruses, and other foreign substances).
• Antibody production is a critical function of the immune system.

Immunoglobulin G (IgG)

• IgG is the most abundant type of antibody.
• It plays a crucial role in the secondary immune response and long-term immunity.
• Can cross the placenta, providing passive immunity to the fetus.
• Neutralizes toxins and pathogens through opsonization, which marks them for destruction.

Immunoglobulin A (IgA)

• Primarily found in mucous membranes, such as the respiratory and gastrointestinal tracts.
• Plays a key role in mucosal immunity, protecting body entrances against pathogens.
• Exists in two forms: serum IgA and secretory IgA, with the latter found in bodily secretions like saliva and breast milk.

Functions of Antibodies

• Neutralization: Antibodies bind to toxins or pathogens to neutralize their harmful effects.
• Opsonization: Antibodies coat pathogens, marking them for phagocytosis by immune cells.
• Activation of Complement System: Antibodies activate the complement system, enhancing the ability to clear pathogens.

Antibody Isotypes

• IgM: First antibody type produced in response to an infection.
• IgD: Functions primarily as a receptor on B cells that have not been exposed to antigens.
• IgE: Involved in allergic reactions and protection against parasitic infections.

Antibody Deficiencies

• Deficiencies can lead to increased susceptibility to infections.
• Reduced levels of IgA and IgG can cause frequent infections and indicate immune system dysfunction.

Key Points from Videos (YouTube)

1. Isotypes: Understanding different antibody classes (IgM, IgG, IgA, IgE, IgD).
2. Opsonization: The process of marking pathogens for destruction.
3. IgG Transfer: How IgG is transferred to the fetus via the placenta.
4. Neutralization: The role of IgG in neutralizing toxins.
5. Where to Find IgA: Common locations of IgA within the body, such as mucosal surfaces.
6. Antibody Structure: The basic structure of antibodies and their components.

Summary

• Antibodies are crucial for immune defense and exhibit various isotypes, each with specific roles.
• IgG and IgA are essential in providing immunity at both systemic and mucosal levels.
• Understanding how these antibodies function and their roles in immune responses can aid in diagnosing and treating immune-related conditions.