TNF and infection: Naïve macrophages can be activated either classically into a proinflammatory M1 phenotype by IFNγ, TNF-α, and TLR ligands to defend against infection or into an anti-inflammatory M2 phenotype by IL-4 and IL-13 to aid in healing (Tan et al., 2016; Srivastava et al., 2017).