CD4 and infection: To examine if CXCR6 expression correlated with the ability of lymphocytes to express cytokines in this acute infection model, leukocytes from the lungs at day 20 after infection were stimulated with the encoded CD4+ T cell epitope, P25, or the endogenous CD8+ T cell epitope, NP366−375, and similarly to M. tuberculosis infection, production of IFNγ (CD4+p < 0.01, CD8+p < 0.01) and TNFα (CD4+p < 0.05, CD8+p < 0.01) correlated with CXCR6 expression (Figure 1G).