An initial lag phase in cytolytic activity precedes robust T cell mediated killing within tumors.

<p>A) ITC assays were performed beginning on days 2, 4, or 6. For tumors, each point represents the mean percent lysis, derived from 2–3 individual mice, for one experiment. Results from 17 experiments are shown, with overall mean values indicated by bars. For dLN and spleen data, each point represents killing from one mouse, with overall means indicated by bars. B) Thy1.1⁺ DUC18 T cells were transferred on day 0, and organs harvested and analyzed on indicated days. Numbers of live Thy1.1 DUC18 T cells are plotted (for tumors, p values for day 2 versus day 4 = .03, for day 2 versus day 6 = .05; for dLNs, p = 0.03 for day 2 versus day 4, and p = 0.04 for day 2 versus day 6). Points represent individual mice (n = 13–20) from 3 experiments. C) Normalized killing values were calculated by dividing the mean % specific killing by the mean number of live DUC18 T cells present in tumors for each time point. D) Activated DUC18 T cells were transferred into tumor bearing mice on day 0. Organs were harvested on days 2 and 6, and the percentage of cells expressing IFNγ ex vivo was determined by intracellular cytokine staining, after gating on Thy1.1⁺ Vβ8.3⁺ DUC18 T cells. E) Linear regression analyses for % specific killing in tumors versus % Meth A reference cells present for all individual mice used in ITC assays shown in A. The slopes were not statistically different from 0; day 2 p = 0.83, day 4 p = .90, day 6 p = .16).