lamoran at gpu.utcs.utoronto.ca (L.A. Moran) writes:
>The defense mechanisms employed by bacteriophage and viruses are very
>sophisticated and have been studied intensely. However, it is unlikely that
>they are evolutionarily related to the immune system in mammals. Similarly,
>the mechansisms employed by plants, arthropods and other invertebrates have
>evolved over a period of hundreds millions of years from the time of the last
>common ancestor of these organisms and vertebrates. Given that there is such
>variety within vertebrates and that the immune systems are so sloppy it
>doesn't seem very likely that there is much of an evolutionary history to
>detect. Very few of the molecules of the vertebrate immune system have an
>evolutionary history that predates the origin of chordates, this suggests
>that most of the vertebrate immune system is fairly new on the scene.
>Laurence A. Moran (Larry)
>P.S. Parts of this posting are deliberately provocative in order to generate
I would argue that large parts of the human immune system are ancient,
if you consider any active defense against invasion as immunity.
I believe that phagocytosis is used as a defense throughout the metazoans,
and it is therefore likely that all metazoans share a common system of
delineating self as far as macrophages (and their ilk) are concerned.
A lot of "low-tech" defenses (such as lysozyme, proteases, nucleases)
are probably also ancient.
Department of Cellular & Developmental Biology
Department of Genetics / HHMI
robison at biosun.harvard.edu