In article <35C781C0.642C at mail.tju.edu>,
mark <mark.haynes at mail.tju.edu> wrote:
>>I'll bite. My guess is 50-250 thousand. The question then is how many
>have self vs foriegn peptides attached. And another question concerns
>thresholds. Lets presume that MHC + peptide + TCR (or ab) send a signal.
>what number or % is needed to be complexed in order that the signal is
>transmitted.
>markH
Almost certainly the vast majority of MHC molecules contain self-peptides,
even in a virally infected cell (I'd guess >90%). As for the number of
MHC/peptide + TCR interactions needed to trigger a T cell, Lanzavecchia's
group has done some elegant work in this field. They calculated that
~8000 interactions were needed to activate a T cell in the absence of
co-stimulation, while ~1500 were needed if co-stimulation was present.
But they didn't all need to happen at once - the TCR's could be triggered
serially (which is good, because most antigenic peptides are present on
the cell surface on the order of 1-50 copies/cell)
Ken Frauwirth
--
Ken Frauwirth (MiSTie #33025) kfrauwir at midway.uchicago.edu
Gwen Knapp Center for Lupus and Immunology Research
University of Chicago
http://www.ocf.berkeley.edu/~frauwirt
