A serum antibody is an antibody derived from serum, a blood component that is collected after blood has coagulated. As it is collected after coagulation, blood serum does not actually contain blood cells or clotting factors. It does, however, include many different types of proteins that are not involved in the clotting process, including antibodies. Antibodies, or immunoglobulins, are specialized proteins that make up a primary component of the immune system by recognizing and, ideally, disabling foreign bodies, including viruses, bacteria, and other illness-causing agents. It is often necessary to isolate a particular serum antibody from animals for research purposes or from people for purposes of diagnosis or treatment.