I was wondering what other folks thought about the role of costimulation
in CD8 T cells, especially via B7/CD28. Most of the literature on this
topic deals with CD4 T cells. Harding and Allison (J. Exp. Med., 177:1791-
6, 1993) showed that in the absence of APCs and CD4 T cells, a normally
non-stimulatory cell line (P815), when transfected with B7, could stimulate
a CTL response (H-2k v. H-2d). The CTL generated by the B7-P815
stimulators could lyse B7-P815 as well as non-transfected P815. If the
B7-P815s were fixed, there was no CTL activation. However, the fixed
stimulators worked if a CD28 mAb was added to provide the costimulation.
The result that sort of surprised me was that IL-2 could be used instead
of CD28 mAb to allow activation with the fixed cells. My questions are:
1) Can IL-2 replace costimulation for CD8 activation? My impression was
that this was not the case for CD4 cells.
2) What if you coated a plate with Class I coupled with peptide, or maybe
anti-CD3, and threw in allogenic T cells and IL-2. Would you get activation?
What does this say about the requirements for costimulation in CD8 T cells?