Monocyte differentiation in intestine-like macrophage phenotype induced byepithelial cells

Macrophages in normal colonic mucosa show a specific and distinct phenotype with low expression of the typical monocyte/macrophage surface antigens CD 14, CD16, and CD11b and T-cell costimulatory molecules. A method for the in vitro induction of a macrophage phenotype similar to this intestinal pheno type is presented. Multicellular spheroids (MCSs) of intestinal epithelial cell (IEC) and control cell lines were cocultured with elutriated monocytes . Surface antigen expression was analyzed by immunohistochemistry and flow cytometry. Interleukin (IL)-1 beta mRNA was measured by quantitative PCR. M onocytes adhered and infiltrated the MCSs within 24 h. In the MCSs of all I EC lines, the typical monocyte/macrophage surface antigens CD14, CD16, CD11 b, and CD11c, which are detectable after 24 h of coculture by immunohistoch emistry and flow cytometry, were down-regulated after 7 days (e.g., for CD1 4 at 24 h, expression was 86% of CD33+ cells; at day 7, it was 11%). A clea r decrease of lipopolysaccharide (LPS)-stimulated IL-1 beta transcription i n monocytes cocultured with IEC MCSs could he observed during the 7-day per iod. For the first time an intestine-like macrophage-phenotype could be ind uced in vitro. Interactions with IECs play an essential role during this di fferentiation, which is of functional relevance, e.g., for LPS-induced cyto kine secretion.