Evolution of an Adaptive Immune System of Defense

All living organisms have innate immune systems that can be used for self-defense. An adaptive immune system that is capable of recognizing specific pathogens and providing protective memory against a second encounter is found only in vertebrate species, however, including humans. Alternative adaptive immune systems have recently been defined in jawed and jawless vertebrates. Both employ lymphocytes with a wide variety of anticipatory receptors, but they differ in that lymphocytes in jawless vertebrates (lampreys and hagfish) use leucine-rich-repeat-based variable lymphocyte receptors (VLR) for antigen recognition, whereas lymphocytes in vertebrates with jaws use immunoglobulin-based receptors for the same purpose. The VLR antigen receptors are expressed in a clonally diverse fashion by separate populations of lymphocytes that resemble our thymus-derived T lymphocytes and bone marrow-derived B lymphocytes. Using parallels and differences between our adaptive immune system and that of lampreys and hagfish, Dr. Cooper will explore interesting questions about how adaptive immunity may have evolved. He will also address the potential for biomedical uses of antibodies found in the primitive lamprey.