Specific Expression of Phagocytosis and Membrane Ruffling Associated Molecule Aif1 by M Cells

Microfold (M) cells are known as antigen uptake intestinal epithelial cells. It has been reported that transcription factor Spi-B acts as a pivotal transcription factor for the development of M cells with inducing M-cell-specific functional protein, Glycoprotein2 (GP2). The DNA microarray analysis of the follicle associated epithelium of Peyer’s patches from Spib^+/+ and Spib^-/- mice revealed M-cell specific expression of Aif1 associating with phagocytosis and formation of membrane ruffling in microglia and macrophages. Confocal microscopic analysis confirmed that Aif1 was specifically expressed in GP2-positive matured M cells. Therefore, we next investigated whether newly found Aif1 is involved in M-cell development and/or function. When the presence of M-cell was examined in Aif1-deficient mice, comparable numbers of M cells were found with wild-type (WT) mice suggesting that Aif1 is not involved in M-cell development. Contrary, however, Aif1-deficient mice showed significant lower particle antigen uptake compared with WT mice, suggesting that Aif1 has an essential role in M-cell transcytosis function. We are now investigating cellular and molecular mechanisms which might be involved in the Aif1-regulating antigen uptake by M cells.