There are a couple of points which I would like to insert into this
interesting thread.
1) Almost certainly some B-cells Ig will be processed to give rise to
peptides which can be presented on their own MHC-II. However it is
difficult to estimate the frequency.
2) During somatic hypermutation the potential peptides which can bind
MHC-II may be lost or gained.
3) Following on from the work of people like Colin Watts who have shown
that when antigen is bound to antibody that the processing of the antigen
is different. I would propose that the processing of the antibody is likely
to be different when it has bound antigen. ie what I am saying is that
some B-cells will present their Ig derived peptides or not, differently,
with and without antigen. Again this is likely to alter during somatic
hypermutation.
I accept fully that the logical way out of this is to say that a naive B-cell
presents for tolerance. However what about activated B-cells undergoing somatic
hypermutation. Experimental evidence shows us that activated B-cells make
highly efficient antigen presenters. So how do you deal with altered
specificity
and idiotype during hypermutation?
Mike Clark, mrc7 at cam.ac.ukhttp://www.path.cam.ac.uk/MikeClark/
--
o/ \\ // || ,_ o Mike Clark, C.U. Dept. Pathology
<\__,\\ // __o || / /\, "to pay for my hobbies I teach
"> || _`\<,_ // \\ \> | immunology and engineer antibodies :-)"
` || (_)/ (_) // \\ \_
