I came across a really interesting article regarding a possible causative mechanism for multiple sclerosis (MS). As you most likely know, MS is an autoimmune disease (similar to IBD and Crohn's) where immune cells misguidedly attack the body's own cells. In the case of MS, the body is attacking the protective sheath around major nerves. In the case of IBD, the body is attacking your intestinal tissue.The above mentioned article found that a viral infection could incite certain rare immune cells to be released in the body that attack both the virus and (in the case of MS) nerve cells. The rare immune cells do this because they have receptors for both the virus' proteins and proteins present in nerve tissue (myelin). I found this research interesting given the recent talk from Amy Proal that I blogged about regarding the viral and bacterial metagenome and the recent study (similar to the MS one) that found a possible link between errant T-cells and diabetes.
The study about MS suggests that there's not necessarily a single virus that causes the disease, but instead a combination of factors that generate the errant T-cells:
The authors explained that it's possible that multiple viruses could influence susceptibility to multiple sclerosis. The ability of any particular virus to contribute to the disease could depend on an individual's own repertoire of other predisposing genes, exposure to other predisposing environmental factors, and the random chance that T cells had been generated that recognize a myelin protein and a pathogen.
Receptors on T cells are randomly generated during their development. This observation helps explain why multiple sclerosis is partly a matter of chance. Some people with a genetic predisposition and environmental exposure develop the disease, while others with similar genetic predisposition and environmental exposure do not.
This suggests some really interesting (and challenging) directions for future research. Many current studies are focusing on finding a single bacteria or virus (e.g. MAP) that someone is infected with or a single genetic mutation (e.g. NOD2) that cause IBD. This is a potentially flawed approach, though. This study suggests that even after the infection is cleared, the errant T-cells that cause the autoimmune reaction may persist (i.e. there's no smoking gun). It certainly makes finding the root-cause difficult! But it suggests a different direction to take research.