Fig. 2. Vimentin-positive immature M cells appear in the area of rapidly proliferative cells of crypts in three rabbit GALTs. After 1 hour in vivo incorporation of BrdU, FAE was dissociated, fixed, permeabilized and labeled with anti-vimentin (red) and anti BrdU (green) antibodies. (A) Half dome epithelium from rabbit appendix revealed with DIC; (B) fluorescent labeling of the corresponding field. BrdU labeling is confined to crypts and the neck of crypts. (C,D) Enlarged fields from the delimited area in A, showing vimentin labeling starting around BrdU-labeled cells in crypts (arrow). (E-G) Vimentin-labeled cytoskeleton in the three GALTs studied is progressively organized along the crypt-dome axis starting from fine apico-basal filaments in the crypts (E), here seen from the top of cells, to pockets in dome flanks (G). Isolated FAE from Peyer’s patch (H) and caecal patch (I) shows the first vimentin-expressing cells around BrdU-incorporating cells of crypts (arrows). Insets in D,H,I show vimentin-positive cells co-labeled with BrdU.
