CD4 and infection: Oseltamivir treatment resulted in increased infiltration of antigen-specific CD4+ T cells in the lungs on day 7- post infection (Fig. 5c), although the proportions of CD 44High and T-betHigh activated Th1 cells and effector cytokine IFN-γ and IL-17 secreting cells of HA-specific CD4+ T cells were comparable to the untreated control mice (Fig. 5c).