Functional expression of costimulatory molecule CD88 on epithelial cells in the inflamed colonic mucose

Background & Aims: Costimulatory signals are essential for T-cell activatio n. The aim of this study was to demonstrate expression of costimulatory mol ecules CD86 and CD80 in human colonic epithelial cells and assess their fun ctional roles in the activation of T cells in inflamed colonic mucosa. Meth ods: CD86 and CD80 expression was assessed by immunohistochemistry of colon ic mucosa, reverse-transcriptionpolymerase chain reaction, and flow cytomet ric analysis of isolated colonic epithelial cells and cell lines. Costimula tory effect of CD86-expressing colonic epithelial cells on purified CD4(+) T-cell proliferation was also assessed at suboptimal phytohemagglutinin sti mulation. Results. CD86 and CD80 messenger RNA was detected in isolated col onic epithelial cells from normal and inflamed mucosa of patients with ulce rative colitis. Immunohistochemistry and flow cytometric analysis of coloni c epithelial cells confirmed cell surface expression of CD86 protein in inf lamed colonic mucosa. Cell surface expression of CD86 protein was increased in the colonic epithelial cell line HT29-18-N2 after interferon gamma stim ulation. Purified CD4(+) T cells proliferated in response to suboptimal phy tohemagglutinin costimulated with interferon gamma-stimulated HT29-18-N2, a nd these proliferative responses were efficiently inhibited by the addition of anti-CD86 monoclonal antibody. Costimulatory effect of CD86-expressing colonic epithelial cells isolated from inflamed mucosa of ulcerative coliti s was also demonstrated at suboptimal phytohemagglutinin stimulation in CD4 (+) T cells. Conclusions: Colonic epithelial cells may act as antigen-prese nting cells, and contribute to the activation off cells through costimulato ry molecule CD86 expression in inflamed colonic mucosa.