Andrew Louka wrote in message ...
>The question asks "why", and not "how do B cells achieve one
I suggest you readup on clonal expansion. This is, in
my opininion, one of the key features that make the
immune response so effective and one of the reasons
that it is most likely that each B cell possesses receptors
of only one specificity.
I have just looked up the topic in "Essential Immunology"
by Ivan Roitt (a basic immunology text).
"Because we can make hundreds of thousands,
maybe even millions, of different antibody molecules,
it is not feasible for us to have too many lymphocytes
producig each type of antibody; there just would not be
enough room in the body to accomodate them. To
compensate for this, lymphocytes which are triggered
by contact with antigen undergo successive waves of
proliferation to build up a large clne of plasma cells which
will be making antibody of the kind for which the parent
lymphocyte was programmed."
Clearly, there are workabouts that could have evolved to
develop such a refined response. However, I think that
those are things you should try and figure out on your
own. I think the way to approach this problem is to start
at the beginning of B cell development and try to imagine
different alternatives to the current system. As yourself
what effect your alternatives would have on a single B
and on the immune response as a whole. I think
that you will find that B cells have evolved very nicely.
Hope this is helpful.