Ulcerative colitis. Light micrograph of a section through an affected tissue. Ulcerative colitis is an inflammatory bowel disease (IBD) that causes inflammation and ulcers in the digestive tract. Ulcerative colitis affects the innermost lining of the large intestine. In most people, symptoms usually develop over time, rather than suddenly. A high power image from the lamina propria show an increased number of inflammatory cells including neutrophils, lymphocytes, plasma cells, histiocytes, eosinophils, and mast cells. Magnification: x400, when printed 10 centimetres high