Bacterial proteases graphic (IMAGE) University of California - San Diego Caption Researchers hypothesize that ulcerative colitis may be triggered by bacterial proteases that damage the colonic epithelium and allow an influx of immune cells to drive further inflammation. Credit UC San Diego Health Sciences Usage Restrictions Use photo credit and caption as shown License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.