UPTAKE OF A GRAM-POSITIVE BACTERIUM (STREPTOCOCCUS-PNEUMONIAE R36A) BY THE M-CELLS OF RABBIT PEYERS-PATCHES

The epithelium associated with the lymphoid follicles of Peyer's patch es differs from the villi epithelium by the presence of M cells. The m ain function of these cells is to take up antigens (inert material, vi ruses and bacteria) from the intestinal lumen. The M cells are able to internalize various different gram-negative bacteria. In order to sho w the M cells ability to interact and take up a gram-positive bacteriu m, we exposed rabbit Peyer's patches to Streptococcus pneumoniae R36a. Using the isolated ileal loop technique, Peyer's patches were incubat ed with a bacterial suspension for varying periods (15, 30, 60, 100 mi nutes). The bacteria were found outside and inside the M cells. The in ternalized streptococci could be found in the M cell cytoplasm, in the cytoplasmic ''pockets'' and inside the intraepithelial lymphoid cells . The finding of internalized bacteria with their damaged walls sugges ts the possibility that M cells are able to modify internalized antige ns in the same way as the antigen presenting cells.