Figure 4. T Ag-specific T_CD8-mediated cytotoxicity and granzyme B secretion in the presence and absence of IDO.

(A) WT and IDO^−/− mice were injected i.p. with C57SV cells. Nine days later, splenocytes from each group, typically consisting of 2–3 mice each, were pooled and used at indicated effector:target ratios against ⁵¹Cr-labeled EL4 target cells sensitized with indicated T Ag-derived peptides. Each data point represents mean ± standard deviation of quadruplicate samples. Similar results were obtained in 2 independent experiments. (B) Splenocytes from T Ag-primed WT and IDO^−/− mice were restimulated ex vivo with site IV, and granzyme B (GrB)-secreting cells were enumerated by ELISPOT as described in Materials and Methods. A representative ELISPOT well for each group is illustrated along with mean ± SEM of GrB spots per 10⁶ splenocytes for 16 WT and 11 IDO^−/− mice.