The Seattle group showed in 1993, I believe, that the CD28 mediated
stimulation is NOT essential for superantigen-mediated T-cell
expansion/proliferation. They used CTLA-4Ig as a B7-directed inhibitor
and saw no effect on Superantigen-induced IL-2 synthesis or proliferation.
Given opportunity, CD28 stimulation may augment the existing
superantigen-induced response but its participation is not obligatorily
required as some people would have us believe.
