Figure 4. Memory CD4 T cell formation following IAV priming is not impaired in the absence of IL-6.

WT or Il6^−/− C57Bl/6 mice were primed with A/Alaska as described in Figure 3. The (a) percentage and (b) absolute number of NP_311–325 tetramer⁺ CD44^high CD4 T cells was enumerated at 45 dpi (n=4 mice/group; one of 2 similar experiments). In separate experiments, WT or Il6^−/− mice receiving 1×10⁶ Thy-disparate naïve OT-II donor cells were primed with 0.1 LD₅₀ A/PR8-OVA_II. At 45 dpi, the (c) percentage and (d) absolute number of donor cells detected in stated organs was determined (n=4 mice/group; one of 2 experiments). The mean fluorescence intensity of CD127 on donor cells was determined by FACS (e). The percentage of donor cells co-producing IFN-γ and IL-2 was determined by intracellular cytokine staining following ex vivo stimulation (f).