Immunoglobulins, also known as antibodies, are proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses. They play a crucial role in the body's defense mechanism by binding to these pathogens, marking them for destruction by other immune cells. There are five main classes of immunoglobulins: IgG, IgA, IgM, IgE, and IgD. Each class has a specific function, such as providing long-term immunity or protecting mucosal surfaces. The presence and levels of immunoglobulins can be measured to assess immune function and diagnose various health conditions.