What is IgG?
Immunoglobulin G (
IgG) is one of the five major classes of immunoglobulins, or antibodies, produced by the immune system. It plays a crucial role in the body's defense against bacterial and viral infections. IgG is the most abundant antibody in human serum, making up about 75% of the total immunoglobulins in the blood.
Structure of IgG
The structure of IgG is Y-shaped, consisting of two heavy chains and two light chains. These chains are connected by disulfide bonds. The molecule has two antigen-binding sites, which allow it to bind specifically to antigens. The Fc region of IgG is crucial for mediating various immune functions, such as binding to
Fc receptors on immune cells and activating the
complement system.
Role of IgG in Immune Response
IgG is essential for the
secondary immune response. When a body is re-exposed to an antigen it has encountered before, IgG is produced in large quantities to neutralize the pathogen. It is also involved in
opsonization, where it marks pathogens for destruction by phagocytes. Additionally, IgG can neutralize toxins and viruses, preventing them from infecting cells.
IgG in Histological Studies
In
histology, IgG is often used as a marker in various staining techniques to identify specific cells or tissues. Techniques such as
immunohistochemistry (IHC) and
immunofluorescence utilize antibodies against IgG to detect proteins of interest within tissue sections. This helps in diagnosing diseases and understanding cellular functions.
Applications of IgG in Diagnostic Pathology
IgG-based staining methods are widely used in diagnostic pathology to identify
cancer cells and infectious agents. For instance, in autoimmune diseases, IgG deposits can be detected in tissues using IHC. This provides valuable information for the diagnosis and monitoring of diseases like
lupus and
rheumatoid arthritis.
IgG in Therapeutics
Monoclonal antibodies, which are engineered versions of IgG, have been developed for therapeutic purposes. These antibodies are designed to target specific antigens, making them effective in treating various conditions, including cancers and autoimmune diseases.
Rituximab and
Herceptin are examples of therapeutic IgG antibodies used in clinical practice.
Challenges and Future Directions
Despite its widespread use, there are challenges in using IgG in histological studies, such as non-specific binding and cross-reactivity. Researchers are continually working on improving antibody specificity and sensitivity. Future advancements in
nanotechnology and
bioengineering hold promise for the development of more effective IgG-based diagnostic and therapeutic tools.
