In article 308fu0INNcre at jhunix.hcf.jhu.edu,
ejf at welchlink.welch.jhu.edu (Ephraim Fuchs) writes:
> Since antigen presenting cells take in antigens randomly from their
> environment, how is their delivery of signal two regulated so as to
> achieve a self/nonself discrimination?
In my opinion it isn't necessary to regulate e.g. the phagocytosis of
macrophages to achieve a self/nonself discrimination at the level of T
lymphocyte activation.
Self/nonself discrimination is achieved by the ability of T-cell receptors
(TCR) of CD4+ T lymphocytes to built a complex with MHC-II, the presented
anigen and the TCR. No complex (MHC-II-antigen-TCR), no signal for the T
lymphocyte.
Normally TCRs won't bind to a complex of MHC-II and self-antigen (negative
selection).
Michael
--
Michael Scheinost Internet: <scheini at bio.rhein-main.de>
CompuServe: <100326,2553>
