Using red blood cells modified to carry disease-specific antigens, scientists at the Whitehead Institute for Biomedical Research, in Cambridge, Mass., prevented and alleviated multiple sclerosis in early stage mouse models. Researchers say the findings could lead to future insights into how the immune system regulates itself and how that sometimes goes awry.
 
Using bits of proteins from the offending cells — antigenic peptides —  researchers have retrained the immune system to ignore the antigens that trigger inappropriate immune responses. This method, called tolerance induction, shows promise, but the technique is fraught with problems, including delivering the antigenic peptides to their destination before they are degraded or beset by immune cells.
 
To sidestep many of these issues, the researchers pressed red blood cells into service. Red blood cells are particularly well-suited for the delivery of molecules throughout the body. Not only do these cells quickly access almost every tissue, they are also recycled every month in mice and four months in humans without triggering an immune response against them. In previous research, the team attached biotin (a chemical tag) and antibodies to red blood cell using a method called “sortagging.”
 
Drawing blood from a mouse, researchers used sortagging to decorate the red blood cells with the antigens that trigger the harmful immune response, and transfused the altered red blood cells back into mouse models of MS. The entire process can be completed in about an hour. In mice, the transfusions reduced symptoms of disease and even a single injection prior to the onset of disease could prevent further symptoms.
 
Results of mouse model studies sometimes do not translate to humans and may be years away from being a marketable treatment. Further, although antigenic peptides can be effective in stimulating the induction of tolerance, the mechanism responsible is not well understood at the cellular and molecular levels. Finally, the researchers also point out that red blood cells used in the experiment are not “immunologically inert.”
 
The findings were published online in the journal PNAS.