Figure 6.

Illustrative sequence of events by which endotoxin (lipopolysaccharide) from Gram-negative bacteria or other bacterial products, such as lipotechoic acid (LTA) from Gram-positive bacteria (Ryu et al., 2009), interact with immune cells via toll-like receptors (TLRs) to initiate a pro-inflammatory cytokine response that induces the systemic hypersecretion of procalcitonin (ProCT) from parenchymal cells. In turn, in a feedback manner, the blood cell production of these same cytokines may further augment the local levels of ProCT.