Immunopathogenesis of severe sepsis.

Severe sepsis refers to the syndrome of fever, hypotension and organ dysfunction resulting from infection, commonly due to Gram-negative or Gram-positive bacteria with or without bacteraemia1. Occasionally, non-bacterial pathogens, including fungi, rickettsiae, protozoa and viruses, can cause a similar syndrome. The first line of defence against infecting organisms comprises highly conserved interactions of the host’s innate immune system with microbial products, followed by amplification of the immune response to maximise host defences. Whilst evidently conferring an evolutionary survival advantage, the humoral and cellular responses which ensue are directly invo lved in the pathogenesis of severe sepsis.