MODIFICATIONS OF THE FOLLICLE-ASSOCIATED EPITHELIUM BY SHORT-TERM EXPOSURE TO A NON-INTESTINAL BACTERIUM

This study was undertaken in order to study the effects of short-term exposure of the follicle-associated epithelium (FAE) of rabbit Peyer's patches to a non-intestinal, Gram-positive bacterium, Isolated ileal loops, each containing one Peyer's patch (PP), were stimulated for sho rt periods of time (30 and 60 min) with Streptococcus pneumoniae R36a, a micro-organism normally not present in the intestinal area, Samples from antigen-stimulated and control Peyer's patches were analysed by Light (LM), transmission electron (TEM), and scanning electron microsc opy (SEM), Stimulation with living pneumococci induced dramatic change s in FAE architecture and morphology, A massive passage of cells from lymphoid tissue to the FAE was rapidly detectable, accompanied by alte rations of the FAE surface, with a marked increase of M-cell area, Fur thermore, TEM analysis revealed that M cells were able to internalize living pneumococci. S. pneumoniae R36a is a valid experimental model f or the further study of the unique antigen sampling function which cha racterizes the highly specialized FAE in Peyer's patches.