SELECTIVE TRANSPORT OF MICROPARTICLES ACROSS PEYERS PATCH FOLLICLE-ASSOCIATED M-CELLS FROM MICE AND RATS

M cells are specialized structures in the Peyer's patch follicle-assoc iated epithelium capable of taking up bacteria, viruses and other path ogens for later presentation to the gut-associated lymphoid tissue. Th e present work studies how coating microspheres with different protein s affects their ability to be taken up by M cells under near physiolog ical conditions in vivo. The later appearance of microspheres in intes tinal lymph has also been measured by flow cytometry. The protein prep arations used in these experiments included bovine serum albumin (bSA) , human immunoglobulin G (hIgG), secretory immunoglobulin A (hIgA), bo vine growth hormone (bGH) and bGH complexed with an IgG antibody raise d against bCH (bGH-Ab). Selectivity in binding of these microspheres t o M cells, determined by confocal microscopy, was bGH < bSA < hIgG (mi ce) and bGH < bGH-Ab (rats and mice). A similar selectivity was seen f or microsphere entry into M cells (bGH < bSA < hIgC; bGH < bGH-Ab). Th e appearance of protein-coated microspheres in rat mesenteric lymph sh owed a similar selectivity to that found for binding and entry into M cells (bCH < bCH-Ab). This latter selectivity was also found for hIgA- coated microspheres (bSA < hIgA). Preservation of transport selectivit y throughout transcytosis highlights the unique importance of the M ce ll surface as being the primary site determining which type of antigen can be presented subsequently to the gut immune system. The possibili ty that this is a transient or phasic property of the M cell surface a nd that this could have physiological relevance is also discussed.