We’ve all heard of the multitude of health benefits that probiotics (friendly bacteria) are thought to offer. More than just freeloaders living in our guts, the little critters seem to keep us healthy by regulating our intestines and staving off infection and disease. But can these organisms also help prevent immune system disorders, from allergies to autoimmune diseases like ulcerative colitis? New research shows just how this might be the case.

Scientists induced the mice to develop a mouse form of colitis that is considered to be similar to inflammatory bowel disease (IBD) in humans. Incredibly, the symptoms of the disease were significantly less severe in Clostridium-treated mice.

In the current study, researchers first gave antibiotics to a group of mice to kill off the bacterial in their intestines. When they measured the number of immune system cells called T cells, the team found that they were much lower than normal, which suggests an interesting positive relationship between bacteria and the immune system.

To explore this further, the researchers gave the same mice various species of harmless Clostridium bacteria to re-colonize their intestines with the friendly microbes. As expected, they found that the number of T cells also shot up.

When the researchers gave Clostridium to normal mice, they found that the T cell levels in their colons were also higher than normal. This finding suggests that even under regular conditions, there is a positive relationship between bacteria and these important immune cells.

Is there a practical application to all of this? Absolutely. The researchers wanted to determine whether the Clostridium-treated mice would also be less likely to develop autoimmune diseases, given their increase in immune system cells. So they induced the mice to develop a mouse form of colitis that is considered to be similar to inflammatory bowel disease (IBD) in humans. Incredibly, the symptoms of the disease were significantly less severe in Clostridium-treated mice, and their colons also appeared to be much less damaged by the disease than the colons of the untreated mice.

While the researchers aren’t exactly sure about the mechanisms behind the "Clostridium-host crosstalk", they are certainly encouraged by the idea that administering beneficial bacteria can ward off serious autoimmune diseases. Of course, it will remain to be seen whether the same holds true for humans. If it is, in the future, then it may be possible to add certain bacteria to foods, as is already the case with some yogurts.

The research was conducted by a team at the University of Tokyo, and published in the December 23, 2010 issue of Science.