An antibody, also known as an immunoglobulin, is a large, Y-shaped protein that is used by the immune system to neutralize pathogens. The antibody recognizes a unique molecule of the pathogen, called an antigen, and neutralizes it. [adapted from wikipedia]. This class represents various types of antibodies, the presence or absence of which are the object of a laboratory test. The antibody is typically represented by a SNOMED code.