The recent discussion on bionet.immunology on the number of blood group
antigens in different species has prompted the question, why do the
number of antigens vary so much from species to species? That is, why
are cats happy to have 95% of the species bearing a single blood type,
while cattle have some 80 or so types?
I've seen speculation that (at least for humans) the different blood types
reduce the spread of red cell parasites, in that the parasites use the
blood types as receptors. I find that unsatisfying, first because it
shows little respect for the parasite's ingenuity and second because it
suggests that cattle should have much less problem with blood parasites
than do cats - which is not the case. (You could say, I suppose, that
cattle made the evolutionary attempt and were forestalled by the
parasites, but that's even less satisfying, not to mention probably
unprovable.)
Anybody know? Failing that, anybody have an interesting wild-assed guess?
Ian
--
Ian York (iayork at panix.com)
Dana-Farber Cancer Institute, 44 Binney St., Boston MA 02115
Phone (617)-632-3921 Fax (617)-632-2627
