Antigens and Antibodies - Lesson 48
An antigen is a substance, usually foreign to the body (such as a poison, virus, or bacterium), that stimulates the production of antibodies. Antibodies are protein substances made by white blood cells in response to the presence of foreign antigens. For example, the flu virus (antigen) enters the body, causing the production of antibodies in the bloodstream. These antibodies will then attach to and destroy the antigens (viruses) that produced them. The reaction between an antigen and an antibody is called an immune reaction (immune/o means protection). Another example of an antigen-antibody in the Rh condition. A person who is Rh+ has a protein coating (antigen) on his or her red blood cells (RBCs). This antigen factor is something that the person is born with and is normal for him or her. A person who is Rh- has normal RBCs as well, but they do not carry the Rh factor antigen. If an Rh- woman and Rh+ man conceive an embryo, the embryo may be Rh- or Rh+. A dangerous condition a...