Final answer:
The five main classes of immunoglobulins in humans are IgA, IgD, IgE, IgG, and IgM, and they play distinctive roles in the immune system, with IgG being the most abundant and involved in fighting infections, while IgA protects mucous membranes and IgE is involved in allergic responses.
Step-by-step explanation:
The five main classes of immunoglobulins found in humans are IgA, IgD, IgE, IgG, and IgM. Each class has unique functions in the immune system:
- IgG is the most abundant antibody in the blood and extracellular fluid, crucial for fighting bacterial and viral infections.
- IgM is often the first antibody produced in response to an antigen and is primarily found in the blood and lymph fluid.
- IgA is found in mucous membranes, saliva, tears, and breast milk, playing a key role in mucosal immunity.
- IgE is associated with allergic reactions and protection against parasitic infections.
- IgD is mainly found on B cells and is least understood, but it plays a role in initiating immune responses.