It seems to me that we ought to go back to the costimulatory molecules
that Paul J. Travers mentioned in an early note. You would expect foreign
antigens to be presented to T cells on cells bearing costimulatory
molecules, while most self antigens would be presented in the absence of
costimulation. According to Liu and Janeway (PNAS 89:3845 1992), the antigens
and the costimulatory molecules must be on the same cell for clonal expansion
of T cells, which explains why tissues can express autoantigens and contain
active antigen-presenting cells without inducing autoimmunity.
Jevnikar and coworkers (Am J. Pathol 141:743 1992) treated lupus-prone
MRL-lpr mice with dexamethasone and htereby prevented lymphadenopathy and
renal injury. I haven't read the article, but in the abstract they suggest
that the role of dexamethasone was to alter the expression of costimulatory
I am sending this message by e-mail and I don't know how to join it to
the thread on this subject, or even if that is possible.