Indication for clinical relevance of immunoglobulin-free light chains in inflammatory bowel disease and irritable bowel syndrome

Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) are interrelated intestinal disorders both associated with increased numbers of mast cells and mast cell activation. Previously, we have shown that immunoglobulin-free light chains (IgLC) are able to mediate experimental colonic hypersensitivity responses via mast cell activation. Here, we demonstrate increased serum concentrations of IgLC of patients suffering from IBD, which are reduced in patients treated with immunosuppressive drugs. Furthermore, we demonstrate that IgLC can be found in the intestinal mucosa and inflammatory lesions in biopsies of IBD patients associated with the presence of plasma cells and mast cells. Increased serum concentrations of IgLC and increased presence of IgLC in intestinal biopsies are also observed in patients suffering from IBS. We propose increased levels of IgLC as potential biomarkers of and as therapeutic targets for IBD or IBS.