Pathogenic bacteria typically elicit a host immune response; however, each of us lives with millions of strains of friendly bacteria (known as commensals) that do not activate the immune system or cause any symptoms.
In the Journal of Clinical Investigation, researchers led by Catharina Svanborg at Lund University in Sweden propose that commensal bacteria act as guardians of their host environment, controlling the quantity and quality of host gene expression in order to prevent an immune response.
To study these responses, Svanborg and colleagues used a strain of E. coli that colonizes the urinary tract but does not cause urinary tract infection symptoms. They found that, unlike bacteria that cause symptoms, the asymptomatic bacteria prevented the activation of inflammatory immune responses.
This study identifies a mechanism by which commensal bacteria may establish a beneficial relationship with their host. In an accompanying Attending Physician article, Patrick Seed discusses how commensal bacteria could potentially be used as therapeutics in patients with recurrent urinary tract infections.
TITLE: Bacterial control of host gene expression through RNA Polymerase II Catharina Svanborg Labmedicin dep of Microbiology, immunology and glycobiology, Lund, SWE