Autoimmune diseases such as multiple sclerosis and type 1 diabetes are the third largest cause of morbidity and mortality in the US. In these and other autoimmune diseases, immune cells mistakenly attack and destroy healthy tissue; in the case of multiple sclerosis, the target is myelin, which creates the protective sheath around nerve cells. As a result of the autoimmune response to myelin, nerve cell communication is disrupted, causing numbness, paralysis and blindness. It has been estimated that about 400,000 people in the US and more than 2 million people worldwide suffer from multiple sclerosis.

Current treatments for many autoimmune diseases involve suppression of the whole immune system, leaving the affected individuals vulnerable to infections and more susceptible to cancer. Rather than suppressing the total immune response, an ideal treatment for autoimmune diseases would instead 'retrain' the immune system to recognize the target tissue as harmless and to tolerate it instead of attacking it.

A team of researchers led by Stephen D. Miller (Feinberg School of Medicine, Northwestern University, Chicago, IL) recently reported successfully doing exactly that in a mouse model of multiple sclerosis. Treated mice had no relapses or symptom flare-ups for up to 100 days after treatment, a time frame that could be equivalent to years in a person with multiple sclerosis.

The treatment strategy combined myelin antigens with nanoparticles 200 times smaller in diameter than a human hair. When these myelin-loaded particles were injected into mice with relapsing experimental autoimmune encephalomyelitis (a model for relapsing-remitting multiple sclerosis, which is the most common form of the disease, accounting for roughly 80% of cases), they were engulfed by macrophages as if they were normal apoptotic blood cells and carried to the spleen, where they were presented to T-cells. This introduction inhibited the attack on myelin and calmed the autoimmune response (Nat. Biotechnol. published online 18 November 2012; doi: 10.1038/nbt.2434).

“This is a highly significant breakthrough in translational immunotherapy,” stated Miller in a press release. “Our approach resets the immune system so it no longer attacks myelin but leaves the function of the normal immune system intact.” The approach could be modified for use in treating other autoimmune disorders as well. According to Miller, “The beauty of this new technology is it can be used in many immune-related diseases. We simply change the antigen that's delivered.” Miller's group plans to test this strategy in people with multiple sclerosis and those with type 1 diabetes.