HETEROGENOUS NA+, K+-ATPASE EXPRESSION IN THE EPITHELIA OF RABBIT GUT-ASSOCIATED LYMPHOID-TISSUES

Na+, K+-ATPase expression in the epithelia of rabbit gut-associated lymphoid tissue was measured using indirect immunofluorescence and confocal laser scanning microscopy. All four major sites of aggregated lymphoid tissue, i.e. Peyer's patch, sacculus rotundus, caecal patch and appendix, were studied. Na+, K+-ATPase expression was localized to the basolateral surface of cells of the follicle-associated epithelium (FAE) and adjacent villous or surface epithelia (non-FAE), where increased expression during enterocyte migration was evident. In the FAE, expression of Na+, K+-ATPase appeared to be lower in the specialized M cells than in enterocytic-type cells, although expression in both cell types was lower than in adjacent non-FAE. Quantification of immunofluorescent staining of Na+, K+-ATPase by confocal laser scanning imaging showed a reduction of expression in the FAE to approximately 20-60% relative to that in the adjacent non-FAE. These results are consistent with a primary role of the FAE in mucosal immunity with minimal involvement in active solute absorption.