IL10 and influenza: IL-10Rα blockade in mice increases the severity of respiratory disease in mice infected with influenza or RSV,93–95 with similar results obtained in RSV-infected Il10−/− mice.95 Importantly, with both viruses, increased severity was not accompanied by increased viral burden, but featured a heightened pulmonary Th1 response,93–95 indicative of a failure to regulate adaptive immunity and tolerate infection in the absence of IL-10 signaling (Fig. 2b).