For example, deletion of Bmal1 in macrophages increases pyruvate kinase M2 expression (PKM2) and lactate production, which is required for expression of the immune checkpoint protein-programmed cell death 1 ligand 1 (PD-L1); mice lacking Bmal1 in myeloid cells are more vulnerable to septic death response to severe infection (Deng et al., 2018). Here, BMAL1 is linked to infection.