As described for a long time, carcinoma-derived Caco-2 cells form a polarized epithelium in culture, whereas HT29-D4 cells are nonpolarized and undifferentiated but can form a polarized monolayer when cultured in a galactose-supplemented medium. Using NF-κB translocation and IL-8 and ICAM-1 gene activation as an index, we have studied the relationship between the differentiation state and the cell response to cytokines. We found that differentiated Caco-2 and HT29-D4 cells were responsive to both cytokines TNFα- and IL-1β-mediated activation of NF-κB but that undifferentiated HT29-D4 cells were unresponsive to IL-1β. However, the expression of endogenous ICAM-1 and IL-8 genes was upregulated by these cytokines in either cell lines differentiated or not. Upregulation of ICAM-1 gene occurred when IL-1β or TNFα was added to the basal, but not apical surface of the differentiated epithelia. Finally, it appeared that in polarized HT29-D4 cells, the IL-1β-induced translocation of NF-κB was connected to PKCδ translocation.