Final answer:
Mammals possess five classes of antibodies: IgM, IgD, IgG, IgA, and IgE. These antibodies have unique structures and functions, such as IgM with its pentamer form for pathogen binding, IgG for long-term immunity, IgA for mucosal defense, IgD for B cell receptor function, and IgE for allergic and parasitic responses.
Step-by-step explanation:
In mammals, there are five primary classes of antibodies, also known as immunoglobulins. These are IgM, IgD, IgG, IgA, and IgE. Each class plays a distinct role in the body's immune response and is critical for adaptive immune responses.
- IgM is typically the largest antibody and is commonly the first produced in a primary immune response. Composed of five four-chain structures, IgM can bind up to ten identical antigens. It is often found in its pentamer form, which gives it high avidity for pathogens.
- IgG antibodies are the most abundant, making up about 80% of all antibodies in the blood. They are known for their role in secondary immune responses, providing long-term immunity. IgGs have heavy chains with one variable domain and three constant domains, enabling them to neutralize toxins and tag pathogens for destruction.
- Located primarily in mucosal areas, IgA plays an essential role in the immune function of mucous membranes. This antibody can be found in saliva, tears, and breast milk, helping to protect against pathogens entering through these routes.
- IgD is less understood but acts as a receptor on naive B cells and plays a role in the initiation of immune responses.
- IgE is associated with allergic reactions and defense against parasitic infections, as it can trigger histamine release from mast cells and basophils.