Immunoglobulins (Ig)

Definition:

Immunoglobulins (Ig), also known as antibodies, are proteins produced by the immune system in response to the presence of foreign substances, such as bacteria, viruses, and other pathogens. They play a crucial role in defending the body against infections and diseases.

Structure:

Ig molecules are composed of two heavy chains and two light chains, linked together to form a Y-shaped structure. The heavy and light chains are held together by disulfide bonds, while each chain contains variable and constant regions. The variable regions determine the specificity of the antibody for a particular antigen, enabling targeted immune responses.

Types:

There are five main classes of immunoglobulins, known as IgG, IgM, IgA, IgD, and IgE. Each class has distinct functions and is present in different amounts in various parts of the body. IgG is the most abundant type in the blood and provides long-term protection. IgM is the first antibody produced during an initial immune response, while IgA is primarily found in mucosal tissues, protecting against infections at body surfaces. IgD has a role in activating B cells, and IgE is involved in allergic reactions.

Functions:

The primary function of immunoglobulins is to recognize and bind to specific antigens, marking them for destruction by other immune cells. This process, called antibody-mediated immunity, can neutralize pathogens, prevent them from entering cells, activate the complement system, and facilitate phagocytosis. Immunoglobulins are also involved in immune memory, where they remember previous encounters with antigens, leading to more efficient and rapid immune responses upon reinfection.

Clinical Significance:

Immunoglobulin levels are measured in medical tests to assess immune system function and diagnose certain diseases, such as allergies, autoimmune disorders, and immunodeficiencies. Additionally, synthetic immunoglobulins can be used as therapeutics to supplement or modulate the immune response in various conditions.