Figure 1. Summary of Corse's findings and the controversy.

Corse and colleagues studied peptides that bind with increasing affinity in the TCR-peptide-MHC interaction. In vitro, T cell response increases as the affinity increases. In vivo, T cell function and expression of signaling-related molecules peaks at an intermediate affinity. The same CD4+ T cells from a transgenic mouse were used in both the in vitro and in vivo experiments. These results contrast with those from related studies using different types of T cells and experimental conditions. Specifically, Zehn and colleagues examined how stimulation of CD8+ T cells from a transgenic mouse responded to cognate peptides with increasing affinity [20] and found a direct correlation between affinity and the number of T cells, as indicated in red. (Signaling-related molecules were not examined in this study.)