SPONTANEOUS SECRETION OF INTERFERON-GAMMA AND INTERLEUKIN-4 BY HUMAN INTRAEPITHELIAL AND LAMINA PROPRIA GUT LYMPHOCYTES

Background-Cytokines secreted by intestinal T lymphocytes probably pla y a critical role in regulation of the gut associated immune responses . Aims-To quantify interferon gamma (IFN-gamma) and interleukin 4 (IL- 4) secreting cells (SC) among human intraepithelial (IEL) and lamina p ropria (LPL) lymphocytes from the duodenum and right colon in non-path ological situations and hi the absence of in vitro stimulation. Patien ts-Duodenal and right colonic biopsy specimens were obtained from pati ents with no inflammation of the intestinal mucosa. Methods-Intraepith elial and lamina propria cell suspensions were assayed for numbers of cells spontaneously secreting IFN-gamma and IL-4 by a two site reverse enzyme linked immunospot technique (ELISPOT). Results-The relatively high proportion of duodenal lymphocytes spontaneously secreting IFN-ga mma (IEL 3.6%; LPL 1.9%) and IL-4 (IEL 1.3%; LPL 0.7%) contrasted with the very low numbers of spontaneously IFN-gamma SC and the absence of spontaneously IL-4 SC among peripheral blood mononuclear cells. In th e basal state, both IFN-gamma and IL-4 were mainly produced by CD4(+) cells. Within the colon, only 0.2% of IEL and LPL secreted IFN-gamma i n the basal state, and 0.1% secreted IL-4. Conclusions-Compared with p eripheral lymphocytes substantial proportions of intestinal epithelial and lamina propria lymphocytes spontaneously secrete IFN-gamma and/or IL-4. These cytokines are probably involved in the normal homoeostasi s of the human intestinal mucosa. Disturbances in their secretion coul d play a role in the pathogenesis of gastrointestinal diseases.