Fig. 2.

Increased T-cell activation by endogenous nonstimulatory peptides at limiting antigen quantities. (a) shows the amount of TCR endocytosis at differing quantities of antigen OVA–K^b expressed on the cell surface of RMA-S cells, either alone or with added nonstimulatory peptides derived from VSV, Erk, or the P815 tumor antigen. Erk and P815 are natural endogenous K^b–binding peptides (Santori et al. 2002). (b) shows the percentage of T cells in conjugates with RMA-S cells treated as in (a). (c) shows the interaction between TCR and CD8 by the FRET signal between CD3ζ–CFP and CD8β–YFP. Used with permission from Yachi et al. (2005)