Anti-Tumor Immune Response Figure 4. Impaired proliferation of CD8 T cells after CY treatment. (A) Draining lymph node cells from tumor-bearing mice treated with saline, CY or gemcitabine (GEM) at day 10 post inoculation were analyzed for Ki-67 expression three days later. Cells shown were gated such that CD8neg cells are CD4 T cells. Data shown in lower panel are mean6SEM (n = 3) from one experiment. ** P,0.01 when PBS is compared with CY (unpaired t test). (B) Adoptively transferred transgenic CD8 T cells fail to proliferate in CY-treated mice. CFSE-labeled HA-specific clone 4 cells were transferred into tumor bearing mice two days before PBS or CY injection and were harvested 7 days later and stained for CD8 expression. Cells shown are gated as CD8+. Data shown in lower panel are mean6SEM (n = 3) from one experiment. * P,0.05 when PBS is compared with CY (unpaired t test). (C) HA-specific MHC class I pentamer staining in untreated and CY-treated tumor-bearing mice. Data shown are frequencies of pentamer+ CD8 T cells per total CD8 T cells in tumor-draining lymph nodes at day 10 post CY injection. ns = not significant (P = 0.06, unpaired t test). (D) CD43 (clone 1B11) expression on pentamer+ CD8 T cells in tumor-draining lymph nodes. Cells shown are gated on CD8+ cells. Representative plots are shown. doi:10.1371/journal.pone.0006982.g004 PLoS ONE | www.plosone.org 5 September 2009 | Volume 4 | Issue 9 | e6982