What are the types of immunoglobulins and their functions?

Immunoglobulins, also known as antibodies, are of five types: IgG, IgA, IgM, IgD, and IgE, each with specific functions.

Immunoglobulins are proteins produced by the immune system to fight against foreign substances like bacteria, viruses, and toxins. They are a crucial part of the body's immune response. Each type of immunoglobulin has a unique role in the immune system.

IgG is the most common type of antibody found in the blood circulation, making up about 75-80% of all the antibodies in the body. It is very effective at neutralising toxins, killing bacteria, and enhancing the phagocytosis process. IgG can cross the placenta, providing the foetus with passive immunity against infections.

IgA is mainly found in body fluids such as saliva, tears, and mucus of the respiratory and gastrointestinal tracts. It plays a crucial role in protecting body surfaces that are exposed to foreign substances. It is also present in colostrum, the first milk produced after childbirth, providing the newborn with passive immunity.

IgM is the first antibody produced in response to an infection. It is primarily found in the blood and lymph fluid. It is larger in size and works as a team to eliminate pathogens. It is particularly effective at killing bacteria and agglutinating cells.

IgD is present in small amounts in the blood. Its main function is to signal the B cells to be activated. When an antigen binds to the IgD antibody on a B cell, it triggers the B cell to proliferate and produce more specific antibodies to fight the antigen.

IgE is associated with allergic reactions and is responsible for the symptoms of allergy. It triggers the release of histamine and other chemicals that cause allergic symptoms. It also plays a crucial role in the body's defence against parasitic infections.

In summary, each type of immunoglobulin has a unique role in the immune system, from neutralising toxins and killing bacteria to triggering allergic reactions and providing passive immunity. Understanding these functions is key to understanding how our immune system works to protect us from various diseases and infections.