: DANGER DANGER .
: Since you originally described this phenomena I believe you have thought
: of this. I assume you believe that the B cell idiotype specific T cells
: have been deleted/anergized prior to infection and therefore do not
: react. But in an active infection when you have DANGER you also have a
: huge amount of B cell somatic mutation generating new idiotypic peptides
: in a proper mileu. Why do these not induce T cell response, or do they?
My proposal is that under no circumstances can a B cell activate a naive
T cell to become an effector cell, and that the consequence of a B cell
presenting antigen to a naive T cell specific for that antigen is tolerance.
Now you might ask, "If B cells induce tolerance in idiotype specific
naive T cells, and if the universe of B cell idiotypes is potentially
equal to the universe of foreign antigens, why isn't the entire immune
repertoire tolerized?"
That is a good question, but I think I have an answer. Since an
antigen-specific T cell will encounter a B cell bearing an idiotype that
looks like the antigen in at most 1 in 1 million B cell encounters, such
tolerizing encounters are probably quite rare. But even if they do
occur, the pool of naive T cells is continuously being replenished by
thymic emigrants. So the T cell repertoire is like the water level in a
bathtub with the drain open (tolerizing encounters with B cells) and the
faucet on (thymic production).
Ephraim Fuchs
ejf at welchlink.welch.jhu.edu
