The study of mucosal immunity has revealed that complex reciprocal interact
ions occur between intestinal intraepithelial lymphocytes (IEL) and intesti
nal epithelial cells (IEC). The present study focuses on the induction of i
nducible nitric oxide (NO) synthase in cocultures of freshly isolated rat I
EL and the rat epithelial cell line IEC-18 after the addition of interleuki
n-1 beta (IL-1 beta), tumor necrosis factor-alpha, or lipopolysaccharide. W
hen IEL and IEC were separated using Transwell chambers, NO synthesis was n
ot induced, indicating that cell-cell contact was required. Culture of IEC-
18 with IEL, even in the absence of inflammatory stimuli such as IL-1 beta,
resulted in upregulation of class I and II antigens on IEC-18, due to the
interferon-gamma (IFN-gamma) that is constitutively produced by IEL. Additi
on of anti-IFN-gamma antibody to the NO-producing cocultures resulted in in
hibition of NO synthesis as well as the upregulation of class I and II anti
gen expression. These data indicate that IFN-gamma production by IEL condit
ions IEC for the expression of other components of the inflammatory process
.