What are the different types of antibodies and their functions?

Antibodies, also known as immunoglobulins, are categorised into five types: IgG, IgM, IgA, IgD, and IgE, each with distinct functions.

Immunoglobulins, or antibodies, are proteins produced by the immune system to identify and neutralise foreign objects such as bacteria and viruses. They are a crucial part of the immune response and are produced by specialised white blood cells called B lymphocytes.

IgG is the most common type of antibody found in the blood and extracellular fluid, allowing it to combat bacterial and viral infections. It is the only antibody capable of crossing the placenta in pregnant women to provide immunity to the foetus. IgG antibodies are involved in the secondary immune response, which is more rapid and effective than the primary response.

IgM is the largest antibody and is the first to be produced in response to an initial exposure to an antigen. It primarily stays in the bloodstream where it can effectively kill bacteria. It is responsible for the primary immune response and is also involved in the ABO blood group reactions.

IgA is found in areas of the body such as the nose, breathing passages, digestive tract, ears, eyes, and vagina. It protects body surfaces that are exposed to foreign substances from outside the body. It is also present in saliva, tears, and breast milk, providing immunity to infants.

IgD is present in small amounts in the blood and is primarily found on the surface of immature B cells, where it plays a key role in the maturation and activation of these cells. Its exact function is not fully understood, but it is believed to regulate the immune response.

IgE is associated with allergic reactions and is responsible for causing the symptoms of allergies. It is also involved in the immune response to parasites. When it recognises an allergen, it triggers the release of substances like histamine, causing inflammation and other symptoms of an allergic reaction.

In summary, each type of antibody has a unique role in the immune system, from fighting infections to causing allergic reactions. Understanding these roles is crucial in the study of immunology and in the development of treatments for immune-related diseases.