Bacterial transcytosis across conjunctival M cells.
OBJECTIVE
Antigen-sampling M cells have been identified in conjunctival tissue overlying lymphoid follicles in rabbits and guinea pigs. Conjunctival M cells in the guinea pig display alpha(2-3) sialic acid on their surfaces, as evinced by selective labeling by Maackia amurensis leukoagglutinin (MAL)-I. Haemophilus influenzae strains OM12, which expresses the HMW1 adhesin for alpha(2-3) sialic acid, and Rd KW20, which lacks HMW1, were used to test the hypothesis that conjunctival M cells translocate large microbes.


METHODS
Fluorescein-labeled bacteria were instilled into the conjunctival sac for up to 130 minutes. Confocal laser scanning microscopy and electron microscopy were used to visualize bacterial distribution.


RESULTS
M cells, but not nonfollicular epithelial cells in the palpebral region, selectively bound and translocated bacteria. By 66 minutes, 423 +/- 165 bacteria/mm(2) of follicle-associated epithelial (FAE) surface were found in three-dimensional reconstructions extending 15.4 mum below the surface. By 127 minutes, the number of bacteria increased to 579 +/- 44/mm(2) of FAE surface and they had moved 50% deeper into the follicle. Coadministration with MAL-I reduced OM12 transport by 61%. Similarly, Rd KW20 uptake was 71% less at 63 minutes and 58% less at 121 minutes, indicating that OM12 uptake is at least partially mediated by binding to alpha(2-3) sialic acid.


CONCLUSIONS
Conjunctival M cells are a port of entry for large microbes and may play a role in initiation of mucosal immune responses against commensal or transient ocular bacterial species and may allow the entry of pathogens.
Petris
Carisa K
CK
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211-7400, USA.
Golomb
Miriam
M
Phillips
Thomas E
TE
D018829:Adhesins, Bacterial / Q000378:metabolism; D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology; D018988:Bacterial Translocation / Q000502:physiology*; D001693:Biological Transport, Active / Q000502:physiology; D015169:Colony Count, Microbial; D003228:Conjunctiva / Q000166:cytology* / Q000648:ultrastructure; D004847:Epithelial Cells / Q000502:physiology* / Q000648:ultrastructure; D006023:Glycoproteins / Q000378:metabolism; D006168:Guinea Pigs; D006193:Haemophilus influenzae / Q000502:physiology* / Q000648:ultrastructure; D018928:Immunity, Mucosal; D007150:Immunohistochemistry; D008297:Male; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D010835:Phytohemagglutinins / Q000378:metabolism; D022161:Transport Vesicles / Q000502:physiology
D018829:Adhesins, Bacterial; D006023:Glycoproteins; C117431:HMW1 protein, bacteria; D010835:Phytohemagglutinins; C100156:leukoagglutinins, plants