In every case, OT-1 T cells “parked” in Selleck HDAC inhibitor mice transduced with the AAV2-gfp control vector served as the control. The results are represented as the mean fluorescence intensity (MFI) in groups of at least five mice (Fig. 3A). In the liver, the presence of AAV-OVA caused the down-regulation of CD62L and up-regulation of CD44 at all time points. The CD127 marker was down-regulated at day 3 and 5, but was restored by 8 weeks. The PD-1 marker was powerfully induced in the AAV-OVA mice from day 3 to week 8. None of these effects was modified in the absence of MHC class II. To determine if this PD-1 high phenotype correlated with impaired function, we tested the ability of these cells to produce interferon-gamma

(IFN-γ). Graphs in Fig. 3B,C show OT-1 cells in wild-type versus MHC II–deficient mice on day 5 (B) and week 8 (C). On day 5, OT-1 cells in both wild-type and MHC II–deficient hosts were capable of making IFN-γ in the presence of antigen. However, by week 8, these cells

made less IFN-γ than those without antigen. Thus, the high expression of PD-1 correlated with loss of function. Tamoxifen mouse In the spleen, the down-regulation of CD62L was clear-cut only at week 8, whereas increased CD44 was seen at day 5 and week 8. These data are consistent with our previous demonstration that the anti-AAV immune response starts in the liver, rather than in lymph nodes.14 The down-regulation of CD127 expression on OT-1 T cells in the spleen was not seen on day 3, but was present at day 5 and week 8. PD-1 was up-regulated in OT-1 T cells on day 5 and week 8, but the level of PD-1 expression was at least 10-fold less than with the OT-1 T cells in the liver; the PD-1 MFI data are shown on the same scale to emphasize this difference. None of these effects were different between normal B6 mice and MHC class II–deficient mice. Effects on OT-1 T cells in the PLN were smaller, but there was up-regulation of CD44 and PD-1 expression on day 5 and at week 8. Again, there was no effect of MHC class II–restricted help on any of these phenotypic changes.

These effects on CD8+ T cell surface phenotype in B6 versus MHC class II–deficient mice agree with Fig. 2, and support the conclusion that CD4+ T helper cells are not involved in the CD8+ T cell response to AAV2-ova–transduced liver cells. These effects of the OT-1 T cell phenotype could be summarized as follows: Endonuclease whereas other markers fluctuated in a similar way in both help-intact and help-deficient mice in all of the organs sampled, the expression of PD-1 was dramatically different. Its expression was very high on OT-1 T cells in the liver; however, this expression was not influenced by the presence or absence of CD4+ T cell help. Figure 3 shows that high PD-1 expression is unique to OT-1 cells in the liver.