Clinical immunology: Culprits with evolutionary ties

Abstract

The cellular organelles we know as mitochondria are thought to have originated as symbiotic bacteria. Indeed, the two use common mechanisms to trigger innate immune responses to injury and infection, respectively.

Figure 1. PAMPs, DAMPs and the inflammatory response

Zhang et al. find that, like bacterial DNA released following sepsis, mitochondrial DNA released by severe trauma can also act through toll-like receptor-9 (TLR9) to activate neutrophils through activation of p38 MAP kinase (MAPK) enzyme. Similarly, formylated peptides released from bacteria and mitochondria in these settings attract neutrophils by the process of chemotaxis to sites of inflammation and injury through formyl peptide receptor-1 (FPR1). In both cases, the outcome may be acute lung injury, as part of the systemic inflammatory response syndrome (SIRS). DAMPs, damage-associated molecular patterns; PAMPs, pathogen-associated molecular patterns.