It was known that T-cells become educated to respond to foreign material, but not to the self. Yet the precise mechanism in that process was not understood. Malfunctions of the immune system can result in several autoimmune diseases, among them rheumatoid arthritis, multiple sclerosis, insulin-dependent diabetes, hemolytic anemia and systemic lupus. And organ implants and skin grafts are now commonly performed using pharmaceuticals that impair the immune system to prevent an immune response to the new organ. Such substances leave the body with few defenses against pathogens, however.
Pharmaceuticals based on their research are under development.
The immune system has two distinct means for dealing with pathogens such as viruses and bacteria. More Receptors Marrack and Kappler, working in the early 1980s, identified the structure of one of two T-cell systems that recognize antigens. The receptors on the surface of lymphocytes, they found, are made by combinations of specialized gene segments. Those segments combine at random to create about a trillion different T-cells in each human being, meaning a huge variety of receptors, each recognizing a different antigen, is possible. Kappler and Marrack subsequently cloned the specialized genes encoding the receptors, allowing for further wide-ranging studies.