NOVEL FEATURES OF THE RESPIRATORY-TRACT T-CELL RESPONSE TO INFLUENZA-VIRUS INFECTION - LUNG T-CELLS INCREASE EXPRESSION OF GAMMA-INTERFERON MESSENGER-RNA IN-VIVO AND MAINTAIN HIGH-LEVELS OF MESSENGER-RNA EXPRESSION FOR INTERLEUKIN-5 (IL-5) AND IL-10

Analysis of the respiratory tract before and after primary influenza virus infection revealed a virus-induced preferential accumulation of a CD8(+) T-cell population that coexpresses mRNA for interleukin-5 (IL-5) and IL-10 with virus dose dependent high levels of gamma interferon. However, cytokine production in lung tissues was not restricted to the T-cell population, since CD3(-) cells were found to express mRNA for various cytokines, including IL-4 and particularly IL-6 and granulocyte-macrophage colony-stimulating factor. These data provide in vivo evidence for a local respiratory tract immune response to influenza virus infection dominated by cytokine-producing CD8(+) T cells.