IL10 and infection: 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.