B Cells Prevent Tissue Repair in Inflammatory Bowel Disease

Researchers at Sweden’s Karolinska Institutet suggest that B cells critical to the proper functioning of the immune system can sometimes do more harm than good by showing up in high numbers at the site of bowel damage and preventing tissue from healing. The findings may be of significance to the treatment of inflammatory bowel disease.

B cells are white blood cells whose immune function includes producing the antibodies that attack bacteria and viruses. Previous research has shown that people with chronic inflammatory bowel disease (IBD), such as Crohn’s disease or ulcerative colitis, have many more B cells in their intestines than healthy individuals. For this reason, it has been proposed that B cells might affect the severity of these diseases. The work at Karolinska Institutet sought to determine if this is the case, and if so, the mechanism behind it. 

The researchers studied an experimental model of colitis and tissue from patients with ulcerative colitis, using a range of methods to analyze cell populations. Focusing particularly on how B cells affect healing in the intestinal mucosa, they found that mice lacking B cells recovered much more quickly after bowel damage than regular mice. The finding that the B cells seem to do more harm than good in colonic inflammation can be of significance to the treatment of IBD.

“We’ve been able to show that the B cell population increases sharply in the colon during the healing of colonic lesions, and that these cells mainly accumulate in areas where the damage is severe,” says principal investigator Eduardo Villablanca, associate professor at the Department of Medicine (Solna), Karolinska Institutet. “This prevents, in turn, the interaction between two other cell types—stromal and epithelial cells—which is needed for the tissue to heal.”

Gustavo Monasterio, a postdoc in Dr Villablanca’s research group at Karolinska Institutet and one of the leading authors, noted that there are already approved drugs that affect the B cell response and that are used for other diseases. “We now want to test if depleting B cells at specific time windows could also work with IBD. We also need to find out if the accumulation of B cells can have a long-term beneficial effect, such as by changing the composition of bacteria in the gastrointestinal tract.”

The findings were published in a recent issue of the journal Immunity.