Ulcerative colitis. Light micrograph (LM) 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. The major histologic changes in ulcerative colitis (UC) are limited to the mucosa and submucosa. There is no transmural inflammation. In the acute stages, there is cryptitis ( crypt abscesses) ( shown here) with an increased number of inflammatory cells within the epithelium as well as the lamina propria, including neutrophils, lymphocytes, plasma cells, histiocytes, eosinophils, and mast cells. Magnification: x100 when printed at 10 centimetres wide. Human tissue.