IRF8 and Granuloma: H&E staining of lung sections at day 15 p.i. evidenced few granulomas in healthy lung parenchyma of both WT-B6 and IRF-8−/− mice (Fig. 2B panels a, d), albeit those of deficient mice appeared less organized with a increased number of mononuclear cells infiltrated (Fig. 2B panels c, f).