Igg test

 In immunology, IgG (Immunoglobulin G) is one of the five major classes of immunoglobulins, also known as antibodies. Antibodies are proteins produced by the immune system in response to the presence of foreign substances, called antigens, such as bacteria, viruses, and other pathogens.

IgG is the most abundant antibody class in the bloodstream, accounting for about 75-80% of all antibodies. It plays a crucial role in the adaptive immune response, which is the part of the immune system that learns to recognize specific pathogens and mount targeted responses against them.

Here are some key features and functions of IgG:

1. Structure: IgG is a Y-shaped molecule composed of four protein chains: two identical heavy chains (H) and two identical light chains (L). The heavy chains have a constant region (Fc region) and a variable region (Fab region), while the light chains have a variable region. The Fc region allows for interaction with various immune cells and molecules, while the Fab region is responsible for antigen binding.

2. Subclasses: There are four subclasses of IgG in humans: IgG1, IgG2, IgG3, and IgG4. Each subclass has distinct properties, including their ability to activate different components of the immune system and their role in specific types of immune responses.

3. Antigen binding: IgG antibodies can specifically bind to antigens on the surface of pathogens. This binding helps to neutralize the pathogens, preventing them from infecting host cells and promoting their clearance by other immune cells.

4. Opsonization: IgG antibodies can act as opsonins, molecules that enhance the process of phagocytosis. They coat pathogens, making them more recognizable to phagocytic cells like macrophages and neutrophils, which then engulf and destroy the opsonized pathogens.

5. Antibody-dependent cellular cytotoxicity (ADCC): IgG antibodies can also trigger ADCC, a process where immune cells, such as natural killer (NK) cells, recognize IgG-coated target cells and release cytotoxic substances to kill the target cells.

6. Maternal transfer: IgG is the only antibody class that can cross the placenta from the mother to the developing fetus, providing passive immunity to the newborn during the early stages of life.

7. Memory response: During an infection or vaccination, B cells produce IgG antibodies that recognize specific antigens. Some of these B cells become memory B cells, which can quickly produce a robust IgG response upon re-exposure to the same antigen, leading to a faster and more efficient immune response.

Overall, IgG plays a critical role in immune defense by neutralizing pathogens, promoting their clearance, and providing long-lasting protection through memory responses. It is a versatile antibody class that contributes significantly to maintaining health and combating infections.