The five classes of immunoglobulins, also known as antibodies, are IgG, IgM, IgA, IgD, and IgE.
These immunoglobulins play critical roles in the immune system, each possessing distinct functions and structures tailored to specific immune responses. They are distinguished by the type of heavy chain they possess.
Here's a breakdown of each immunoglobulin:
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IgG (Immunoglobulin G): The most abundant antibody in the blood and tissue fluids, IgG provides long-term immunity against infections. It is the only antibody that can cross the placenta, providing passive immunity to the fetus. IgG plays a role in neutralizing toxins and opsonizing pathogens (making them more susceptible to phagocytosis).
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IgM (Immunoglobulin M): The first antibody produced during an immune response. It is a large pentameric molecule (composed of five subunits) and is very effective at activating the complement system, leading to the destruction of pathogens. IgM is primarily found in the blood.
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IgA (Immunoglobulin A): Found in mucosal secretions such as saliva, tears, breast milk, and respiratory and gastrointestinal tract fluids. IgA provides protection against pathogens at mucosal surfaces, preventing their attachment and entry into the body. IgA exists as a monomer in serum and a dimer in secretions.
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IgE (Immunoglobulin E): Primarily involved in allergic reactions and parasitic infections. IgE binds to mast cells and basophils. When an allergen binds to IgE on these cells, it triggers the release of histamine and other inflammatory mediators, leading to allergy symptoms.
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IgD (Immunoglobulin D): Found on the surface of B cells, where it acts as a receptor for antigen. IgD plays a role in B cell activation and differentiation, but its exact function remains less well understood than that of the other immunoglobulins.
In summary, each immunoglobulin class contributes differently to the body's defense mechanisms, providing specialized immunity against a wide range of threats.
