CD4 and infection: T cells expressed negligible amounts of IL-10 or IFN-γ in the lung and bronchoalveolar lavage fluid (BAL) on day 4 post RSV infection (not depicted), but both CD4+ and CD8+ T cells from the lung or airways frequently expressed IFN-γ and IL-10 on day 8 post infection (Fig. 1A and B).