The immune response to severe bacterial infections: consequences for therapy.

The immune response to a bacterial stimulus starts when pathogen-associated molecular patterns of the bacterial pathogens activate pattern recognition receptors of the innate immune system. This leads to production of proinflammatory and anti-inflammatory mediators aiming to contain infection and drive the clinical signs of sepsis. When sepsis and signs of failing organs are apparent, proinflammatory phenomena have ceased; a hypoinflammatory phase predominates, characterized by anergy of monocytes and apoptosis of T lymphocytes. The above sequence of events seems to differ from one patient to the next. The majority of therapies targeting the immune responses have failed to provide clinical benefit. Immunostimulation with IFN-γ and leukocyte growth factors, hemoperfusion with polymyxin B-embedded fiber column, and macrolides remain the most promising immunomodulators in clinical practice.