Dr. Kirberg,
Since you are at Basel, you may wish to talk to Franca Ronchese (if she
is still there; I do not know). She did a neat experiment where she
adoptively transferred F1 (b x d) T cells and B cells into scid (H-2d)
mice, followed by priming with soluble antigen. While this priming was
accompanied by vigorous antibody production, the primed T cells were
restricted only to H-2d and not to H-2b. Obviously, because the F1 B
cells were making antibody, they were activated and interacting with T
cells. Yet no H-2b restricted helper T cells were activated. H-2b
restricted T cells were generated if the adoptive transfer also included
F1 professional APC. So it appears that activated B cells are unable to
prime the precursors of CD4+ T cells that give help in antibody
production.
Maybe we are agreeing, and this is just semantics. However, the bottom
line, I believe is that no B cell, resting or activated, can prime naive
T cells, but they can reactivate memory T cells.
By the way, I don't trust transgenic T cells. They have more than one
species of antigen-specific receptor on their surface and so can acquire
memory from a pairing of endogenous alpha chain and transgenic beta chain.
The reason that all this is important to the original discussion is that
if B cells fail to activate naive T cells, then the immune system CANNOT
discriminate self from nonself because any antigen, self or foreign,
presented exclusively by B cells will tolerize naive T cells specific for it.
Thus one must look for a new paradigm of immune function.
Ephraim Fuchs
ejf at welchlink.welch.jhu.edu
