Enhanced intramucosal cytotoxic lymphocyte gene expression in ulcerative colitis

Abstract

: The histopathology of the mucosal lesions in ulcerative colitis suggests that cellular immune hyperactivity plays a role in the pathogenesis of ulcerative colitis. The role of colonic mucosal cytotoxic lymphocytes in ulcerative colitis is highly controversial. In vitro determinations of cytotoxic lymphocyte function vary according to the experimental conditions and target cells employed. Transcription of the cytotoxic molecules granzyme B and perforin are specific for activated cytotoxic lymphocytes. We investigated whether activated cytotoxic lymphocytes are present in ulcerative colitis lesions via identification of granzyme B, perforin, and interleukin 2 transcripts. RNA was extracted from endoscopic colonic biopsies taken from normal and ulcerative colitis patients. An aliquot was reverse transcribed, followed by gene amplification in the polymerase chain reaction. A competitive template was incorporated within the reaction permitting the quantitation of specific mRNA species. Granzyme B and perforin levels of reverse transcribed cDNAs (RT-cDNAs) were significantly elevated in active ulcerative colitis as compared to normal colonic tissues (p = 0.0081 and p = 0.0018, respectively) when calculated as a ratio with the RT-cDNA of the constitutively expressed gene GAPDH. Interleukin 2 mRNA measurements did not vary between normal and UC samples to a statistically significant degree. These data suggest heightened lymphocyte cytotoxic function within ulcerative colitis mucosal lesions.