Antibodies are a type of small-sized protein that circulates in the bloodstream, and are included as part of the immune system. Antibodies have an important function for the body as a bulwark against various causes of disease. Antibodies are made by white blood cells in response to help the body fight bacteria, viruses, and poisons, and protect the body from various diseases and infections. Antibodies work specifically by sticking to antigens, which are foreign objects in the body that are suspected of being a threat by the body's defense system. Recognizing the Type of Antibody There are several types of antibodies, each of which has its own function, also known as immunoglobulin. The following are the types of antibodies: Immunoglobulin A (IgA) IgA antibodies are the most common type of antibody found in the body, having a role in the emergence of allergic reactions. IgA is found in high concentrations in the mucous lining (mucous membranes) of the body, especially th...