Coordinate regulation of complex T cell populations responding to bacterial infection.

Bacterial infections activate complex T cell populations that differ in size and antigen specificity. We used tetramerized MHC class I molecules complexed with Listeria monocytogenes-derived epitopes to characterize four distinct CD8+ T lymphocyte populations during bacterial infection. Surprisingly, T cell populations differing in antigen specificity expand, contract, and enter the T cell memory compartment synchronously. Because the four L. monocytogenes epitopes are presented with different efficiencies and have distinct stabilities in infected cells, our findings suggest that these factors do not determine in vivo T cell dynamics. While T cell activation requires antigen presentation, the timing and extent of T cell expansion appear to be regulated in a coordinated fashion independent of antigen quantity and stability.