Notably, even though the absolute number of IL-10/eGFP-expressing (IL-10 mRNA +) CD8+ and CD4+ continued to increase in the lungs from d5 to d7 post infection, the in vivo release of IL-10 protein in the airway peaks at d5 post infection, which coincides with the fall in lung virus titers and so the viral antigen load in the lung. The gene discussed is CD4; the disease is infection.