La polarisation des macrophages, le noeud gordien des infections bactériennes ?

Abstract

L’analyse de l’expression génique montre que les macrophages développent un programme commun de réponse aux infections bactériennes de type M1. Cette signature M1 est associée au contrôle des infections aiguës mais, exagérée, elle peut être délétère. Différentes bactéries pathogènes préviennent la polarisation M1 ou promeuvent une polarisation M2 associée à la persistance bactérienne. Des données récentes montrent que l’évolution chronique des maladies infectieuses est liée à la reprogrammation M2 des macrophages. Le diagnostic et le pronostic des maladies infectieuses peuvent s’enrichir de ce nouveau concept de polarisation fonctionnelle des macrophages.

Converging studies show that M1 and M2 macrophages are functionally polarized in response to host mediators. Gene expression profiling of macrophages reveals that various bacteria induce the transcriptional activity of a common host response that includes genes belonging to the M1 program. The microbicidal machinery of M1 macrophages allows them to participate to the clearing of acute infections. However, excessive or prolonged M1 polarization can lead to tissue injury and contribute to pathogenesis. The so-called M2 macrophages play a critical role in the resolution of inflammation by producing anti-inflammatory mediators. These M2 macrophages cover a continuum of cells with different phenotypic and functional properties. Different bacterial pathogens escape from clearing by manipulating functions of M1 macrophages. It has recently been demonstrated that specific M2 programs induced in macrophages by bacterial pathogens are associated with the chronic evolution of infectious diseases.