Expression of membrane-bound scFv. (A) Expression
of membrane-bound scFv on the surface of I-Ek-expressing
CHO cells. Solid histograms represent binding of CTLA-4 Ig to CHO
cells, and shaded histograms represent binding of CD28 Ig to CHO cells.
(B) AND TCR transgenic T cells were purified and
cocultured with costimulatory receptor-specific APC. □, TCR
stimulation alone; ■, TCR/CTLA-4 stimulation;
▵, TCR/CD28 stimulation; ▴, TCR/CD28/CTLA-4
stimulation. Proliferation was measured at 72 h, and IL-2
production was assessed at 60 h.