Innate and adaptive immune responses in patients with pandemic influenza A(H1N1)pdm09.

Innate and adaptive immune responses play critical roles in the body's defense against viruses. We investigated the host immune response against the 2009 pandemic H1N1 influenza virus [A(H1N1)pdm09] in patients before and after anti-influenza therapy and found that the numbers of dendritic cells and T cells were significantly reduced compared with those of a healthy control group. In contrast, the frequency of natural killer, γδT and T regulatory (Treg) cells increased, and the concentrations of plasma interferon (IFN)-α/γ and interleukin (IL-15) were significantly higher than those of the control. Following therapy the frequency of γδT and Treg cells returned to normal; the counts of myeloid dendritic and plasmacytoid dendritic cells were still lower than the control, while the concentrations of IFN-α/γ and IL-15 remained high. We show that infection with A (H1N1)pdm09 was accompanied by changes in peripheral blood lymphocyte subgroups and cytokine profiles, leading to deleterious imbalances in innate and adaptive immunity.