TLR4 and infection: Some literatures show that TLR4 is upregulated when stimulated by M. tb or virulence proteins and subsequently activates a series of signaling pathways and increases pro-inflammatory cytokines expression, and some literatures show that TLR4 is downregulated during infection (Saraav et al., 2014; Kim et al., 2018; Shi et al., 2018; Jang et al., 2019; Li and Zhang, 2019).