The Involvement of Macrophages in the Function and Maintenance of the Intestinal Epithelium

Our aim is to investigate the involvement of macrophages in the development, function and maintenance of the intestinal epithelium. Our data suggests that macrophages have an influence in the composition of the intestinal epithelium. We treated mice with an anti-CSF1R monoclonal antibody (M279) for 6 weeks which resulted in a complete ablation of macrophages in the gut (Sauter et al. 2013). Subsequently, we observed depletion of Paneth cells in intestinal crypts and reduction in M cell density in the follicular associated epithelium (FAE). These data suggest that macrophages may have a more intimate relationship with Paneth cells than previously understood and influence the intestinal epithelium by providing a scaffold for intestinal crypt proliferation function. In a sister study we treated mice with anti-CCL6 and anti-CCL9 antibodies which were previously described to be expressed exclusively by M cells in the FAE (Kobayashi et al. 2012). These chemokines were suspected to be involved in the chemoattraction of antigen presenting cells to the pockets of M cells to initiate antigen sampling. We found depletion in M cell post anti-CCL9 antibody treatment; however no difference was found in M cell densities in mice treated with anti-CCL6.