Phenotype of exogenous microparticle-containing pigment cells of the human Peyer's patch in inflamed and normal ileum.

OBJECTIVES: Pigmented cells, that contain inert, submicron-sized dietary particles, are a consistent feature of the base of human Peyer's patches (PP). We aimed (i) to phenotype these intestinal pigment cells (PC) in archival tissue specimens and (ii) to establish whether PC phenotype is altered in inflammatory conditions, especially Crohn's disease (CD).
METHODS: PCs contained within PP were identified by routine haematoxylin and eosin (H&E) staining and dark field microscopy of archival ileal sections for: adenocarcinoma (n=16), colonic CD (n=23), non-CD colitis (n=10). Paraffin-embedded serial sections were graded for microscopic inflammation and then investigated immunohistochemically with antibodies against CD68, MAC387, CD14, CD11b, CD15, CD1a, S100, HLA-DR, CD86 and Cathepsin D. Analyses were by light and confocal microscopies.
RESULTS: The majority of PCs were CD68 positive (circa 80%) with a minority (circa 20%) staining for MAC387. Microparticles were mainly identified within cathepsin D negative lysosomal compartments. Histological inflammatory grade and disease type had no influence on cell phenotype.
CONCLUSIONS: The microparticle-containing PCs of the PP base are mainly mature macrophages (CD68) of low metabolic and immunological activity. There is no evidence of differential PC phenotype or activation in differing disease states, including CD.