Rusty is a 26
year old llama. He is on a special ration and we should not feed
Rusty lives across the parking lot from our lab in the Stevenson
Center. He is not really ours at all. But we like him and he
seems to like us. His hobbies are grazing and expectoration.
So why the heck would a lab that studies sharks and frogs want a
llama as a mascot? Especially one with Rusty's manic temperament?
While his terrific posture and handsome eyes help, the real answer
lies in his humoral immune system!
Antibodies are made by B cells and they are
comprised of heavy and light chains... usually! In a beautiful example
of homoplasy, both cartilaginous fish and camelids have evolved
antibodies that use pairs of heavy chains, but with no light
chains. These two very divergent groups of vertebrates both
convergently arrived at this antibody innovation in their
evolution. The stability and single-variable domain paratopes of
these antibodies are being exploited for diverse applications. The
sharks appear to go a step further and use a relative of the single
chain variable on some T cells, we call this
NARTCR. (No, even this wonderful molecule does not protect
sharks from cancer.) Incredibly, early mammalian lineages
(marsupials and monotremes) use a similar T cell
receptor usually with two variable domains as well, yet from a
different locus. More gorgeous convergent evolution demonstrating
the diverse paths that have arrived at similar contrivances in
lymphocyte receptor repertoires.
So if in the area, go visit this nice camelid. He has a a
repertoire of antibody structures that most of us bony Teleostomi
can only dream of! Call his name and he'll come running... but if
the ears drop back you might want to take cover.