CCL2 and influenza: Furthermore, the similar expression levels of IFN-β and CCL2 (among others) by alveolar macrophages isolated from influenza-infected WT and Tpl2-/- mice suggest that dysregulated cytokine responses in influenza-infected Tpl2-/- mice likely originate from other cellular sources, like the pulmonary epithelial cells that are primary targets and replicative niches for influenza.