Immunity in the Land of Nod(-like Receptors)
When a pathogen, such as a bacterium or a virus, first enters our body, our innate immune system kicks in, alerting microbial sensors to the presence of an intruder. This immediate response is designed to prevent the invading pathogen from travelling any deeper into our tissues. The sensors trigger inflammatory mediators, the secretion of anti-microbial peptides, and the recruitment of a battery of immune cells to help fight off infection.
Certain pathogens, however, especially food-borne bacteria such as salmonella and listeria, are somehow able to evade these sensors and pass through our natural defence barrier unhindered. Canada Research Chair Stephen Girardin wants to know exactly how the pathogens manage to do this.
In pursuit of his goal, Girardin works with a recently discovered family of intracellular protein sensors called the Nod-like receptors, which can recognize bacterial cell-wall components and are known to play key roles in innate immunity by triggering inflammatory pathways when they detect invading pathogens. Acting like molecular sentinels against infection, the Nod-like receptors regulate inflammation and the immune defences at the level of mucosal surfaces, such as the intestine, and they may be involved in Crohn’s disease, a debilitating inflammation of the intestine that is believed to be an autoimmune disorder.
In Girardin’s lab, he and his colleagues dissect the signalling pathways that are triggered by Nod-like receptors once they detect the incoming microbe. In addition, the scientists work on identifying new sensors in the family of Nod-like receptors and exploring how pathogenic bacteria have evolved to escape our body’s innate immunity.
Girardin’s research is not only broadening our understanding of various food-borne human diseases but is also clarifying the mechanisms that lead to certain important inflammatory disorders at the mucosal surfaces.