The aim of this work was to establish a new, simplified in vitro model of the human M-cell. Cocultures of physically separated human intestinal epithelial Caco-2 cells and B-cell lymphoma Raji cells were established. The cocultures were characterized under the criteria of morphology, integrity, expression of M-cell markers and cell adhesion molecules (CAMs), and altered particle transport, Using this construct, the epithelial cells were transformed to cells with an Rf-cell-like morphology and had altered expression of potential human M-cell markers (alkaline phosphatase down-regulation and Sialyl Lewis A antigen upregulation). The expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule was altered and there was an increased binding of lectins wheat germ agglutinin and peanut agglutinin with a 40-fold increase in microparticle transport. The particle transport was size-dependent and could he inhibited at 4 degreesC or by replacing the Raji B-cells with Jurkat T-cells. This new coculture model will enable controlled studies of M-cell development and function in vitro.