Toll-Like Receptors, New Horizons in Sepsis

Saulo F. Saturnino; Marcus V. Andrade

Abstract

Sepsis and septic shock, its more severe form, have shown alarming increases in incidence and a persistently high mortality rate, despite technological advancement allowing adequate support of vital functions in intensive care units. Progress in understanding of physiopathology has directed the therapeutic approach, until recently limited to sustaining failing organ systems and combating infectious agents, towards the alterations provoked by an unbalanced systemic inflammatory response and its deleterious effects on cellular function. Less than 10 years ago, the discovery of Toll-Like Receptor proteins, which allow the detection of pathogen molecular patterns, initiate and modulate the immune response, opened up new and exciting possibilities in approaches to sepsis. The elucidation of the transduction pathways triggered by Toll- Like Receptors activation signals exposes promising therapeutic targets. Currently, mechanisms associated within the context of Toll-Like Receptor signalization are identified in the tolerance phenomena described in the past. The description of genetic polymorphisms associated with Toll-Like Receptors, and the different patterns of response to infectious insults have defined high-risk subgroups of imbalanced immune response with greater specificity. A better understanding of the molecular structures involved in the process and the negative-regulation of some of them have opened up possibilities in antagonizing and modulating the response to the inflammatory activation mediated by Toll-Like Receptors. Having understood how the immune system recognizes pathogens and organizes the inflammatory response upon the discovery of Toll-Like Receptors and their signaling pathways, we gained an insight into the possibilities of specific treatment instead of supportive measures for sepsis.

Keywords: Toll-like receptor, sepsis, septic shock, signal transduction, immune tolerance, innate immunity, pathogen-associated molecular patterns, pattern recognition receptors