title: Analysis of adhesion molecules involved in leukocyte homing into the basolateral pockets of mouse Peyer's patch M cells.
abstract: The basolateral membranes of intestinal M cells are invaginated to form large intraepithelial "pockets" that are populated by specific sub-sets of mucosal leukocytes, including CD4+ T cells, memory and naïve B cells, and occasional dendritic cells. The adhesion molecules involved in leukocyte trafficking and/or retention within this unique immunological niche are unknown. In this study, we used immunofluorescence microscopy and a battery of monoclonal antibodies to identify the adhesion molecules expressed by leukocytes situated within the intracellular pockets of mouse Peyer's patch (PP) M cells. M cell associated leukocytes (MAL) consistently stained positive for integrin alpha4beta7, and integrin LFA-1 (CD11a/CD18), but were rarely positive for L-selectin (CD62L) or the mucosal integrin alphaEbeta7. However, neither the alpha4beta7 ligands MadCAM-1 or VCAM-1, nor the LFA-1 ligand ICAM-1, were detected on M cell basolateral membranes. To determine whether integrins alpha4beta7 or LFA-1 play a functional role leukocyte homing to M cell pockets, we examined M cells in mice deficient in integrin beta7 or CD11a/CD18. Although PP from CD18 or integrin beta7 mice were reduced in number and size as compared to age-matched controls, we identified M cells in both strains of mice. However, mice lacking CD18 (but not integrin beta7) had significantly fewer leukocytes within M cell pockets as compared to control animals, suggesting LFA-1 (but not alpha4beta7) may contribute, in part, to leukocyte trafficking into and/or retention within this unique immunological niche.
authors.affiliation: GI Cell Biology Laboratory, Children's Hospital Boston, 300 Longwood Avenue, 02115 Boston, MA, USA. nicholas.mantis@tch.harvard.edu
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Mantis
authors.forename: Jessica
authors.initials: J
authors.lastname: Wagner
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000172:deficiency / Q000276:immunology* / Q000502:physiology; D005260:Female; D007962:Leukocytes / Q000276:immunology* / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D010581:Peyer's Patches / Q000276:immunology* / Q000502:physiology; D010641:Phenotype
chemical_list: D015815:Cell Adhesion Molecules