Figure 5.

In vitro cytotoxicity analysis showed the induction of cytotoxic CD8+ T cells by antigen-specific TCV. (A) CD4+ cells isolated from TCV or nonimmunized rats were stained with high or low concentrations of CFSE, sorted depending on Qa-1 high or low by flow cytometry, and cocultured alone or with TCV CD8+ T cells. (B) Qa-1 high CD4+ cells were significantly eliminated when cocultured with TCV CD8+ cells (**P<0.01), but CD4+ Qa-1 low cells were not eliminated. Anti–Qa-1 antibody inhibited the cytotoxic effects of TCV-derived CD8+ T cells on Qa-1 high CD4 T cells. (C) In vitro cytotoxicity assays were performed using CD4 target cells and CD8 effector cells from rats that had received either Fx1A TCV or CFA TCV using the same method as in A and B. There was no effect for CFA-derived CD8+ T cells to eliminate Qa-1–expressing CD4+ T cells in vitro compared with the cytotoxicity of CD8+ T cells isolated from Fx1A-derived TCV rats that were added to Qa-1 high CD4+ T cells in coculture. These results are representative of three independent experiments.