Evolution of the Immune System
30th December 2005
Immunology: Jawless Fish Have Form of Adaptive Immunity, Science Next Article
Excerpts:
Evolution doesn’t like to do things just once. It came up with flight three times, for example–in insects, birds, and bats. Now it appears that evolutionarily distinct immune systems have exploited a similar genetic trick to battle microbes. New research on page 1970 reveals that the immune defenses of jawless fish such as lampreys generate as much diversity as the immune system that organisms from sharks onward in evolution use. And both employ a similar technique: rearranging DNA.
The immune system in sharks, mammals, and other jawed vertebrates generates antibodies–proteins that recognize very specific molecular features of invading pathogens–by rearranging DNA segments and inducing random mutations to give rise to a hundred million million different possible proteins. This allows the immune system to adapt to each new infectious agent by boosting production of antibodies specific for the attacking microbe.
Researchers don’t yet know whether the lamprey’s immune system arose before our own or if it spun off from its own evolutionary tangent, but they’re impressed by its sophistication. “It’s just fascinating that there’s another adaptive immune system,” says David Davies of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland, who studies Toll-like receptors, other immune proteins that recognize pathogens.
Whether vertebrates started out with a [lamprey-like] system and later gave it up for the antibody-based immunity is anybody’s bet. The study authors are looking both in invertebrates–squid and octopus–and in bony fish for remnants of such a system. “It may well be that this exists in us because nature very rarely throws things away,” says Davies.
* Source: Immunology: Jawless Fish Have Form of Adaptive Immunity, Mary Beckman, Science : Vol. 310. no. 5756, pp. 1892 – 1893, 12/23/05