PRODUCTS OF ENTEROPATHOGENIC ESCHERICHIA-COLI INHIBIT LYMPHOKINE PRODUCTION BY GASTROINTESTINAL LYMPHOCYTES

Previously we have shown that lysates of enteropathogenic Escherichia coli (EPEC) inhibit lymphokine production by mitogen-activated periphe ral blood mononuclear cells (PBMCs). The aim of the present study was to determine whether products of EPEC alter lymphokine expression by g astrointestinal mucosal lymphocytes. Lysates from EPEC clones inhibite d mitogen stimulated interleukin-2 (IL-2), IL-4, IL-5, and interferon- gamma (IFN-gamma) but not IL-8 mRNA expression by lamina propria monon uclear cells isolated from surgically resected colon specimens. Inhibi tory lysates did not significant change CD25 expression on either CD4, CD8, or CD45R0 lymphocytes by flow cytometry. Bacterial supernatants of EPEC inhibited IL-2 and IL-5 protein secretion by mitogen stimulate d PBMCs. EPEC lysates inhibited IL-2 mRNA expression induced by lysate s of nonpathogenic E. coil. In conclusion, EPEC contains a novel gene( s) that encodes factors that selectively inhibit IL-2, IL-4, IL-5, and IFN-gamma expression by mucosal mononuclear cells without affecting C D25 or IL-8 expression. Thus enteric bacteria can produce factors that may regulate the function of the gastrointestinal mucosal immune syst em.