PTPRC and ulcerative colitis: Small populations of non-epithelial cells (identified by expression of CD45) were also present in disaggregated crypt cell preparations from normal control colon [1·5 (s.e.m. ± 0·4)%], ulcerative colitis [2·4 (s.e.m. ± 1·3)%] and colonic Crohn's disease [2·5 (s.e.m. ± 0·7)%] tissue.