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.

Immunolocalization of duodenal cytochrome B: a relationship with circulating markers of iron status.

BACKGROUND: The brush border ferric reductase (Dcytb) is critical for the absorption of dietary iron and appears to be expressed on the duodenal enterocyte brush border. The Dcytb expression is increased in severe iron-deficient anaemia, but the situation in a more typical mild iron deficiency is unclear. This study investigated Dcytb expression in patients with normal iron status or mild iron deficiency and its relationships with enterocyte iron status. MATERIALS AND METHODS: Duodenal biopsy specimens and blood samples were obtained from 32 patients undergoing routine upper gastrointestinal endoscopy. Twenty-three specimens (six iron-deficient and 17 iron-replete) were processed for light-microscopy (LM) and for immunohistochemistry with antibodies against Dcytb and heavy/light chain ferritin subunits. The nine remaining biopsies (three iron-deficient and six iron-replete) were processed for electron microscopy (EM). Immunolocalization of Dcytb and intracellular ferritin was performed with appropriate primary antibodies followed by 10-nm gold conjugate labels. RESULTS: The LM process showed a strong negative correlation between immunolabelling intensity of Dcytb on the enterocyte brush border and serum iron saturation (P < 0.001), but only a weak negative correlation between this antigen and haemoglobin (P = 0.08) or serum ferritin concentrations (P = 0.4). EM confirmed anti-Dcytb preferential labelling of microvilli rather than enterocyte cytoplasm (P = 0.001), but preferential antiferritin labelling of cytoplasm (P < 0.02). There was no correlation with enterocyte cytoplasmic ferritin labelling (i.e. enterocyte iron status and Dcytb expression). CONCLUSIONS: Enterocyte Dcytb brush border expression is increased even in mild iron deficiency and may be related to serum iron saturation. The lack of correlation with enterocyte ferritin expression deserves further study with direct measurement of intracellular iron.

Related IgA1 and IgG producing cells in blood and diseased mucosa in ulcerative colitis.

BACKGROUND: Ulcerative colitis (UC) is a chronic inflammatory bowel disease in which the colonic mucosa is infiltrated with plasma cells producing IgG autoantibodies. It is not known whether this represents a local mucosal response which has switched to IgG or a peripheral response which may have been initiated by peripheral antigen which homed to the colonic mucosa. The clonal distribution of IgG secreting cells and isotype switched variants in UC is not known. AIMS: To investigate the clonal distribution of mucosal IgG in UC and to search for related IgG and IgA secreting cells in normal and diseased mucosa and blood in UC. To investigate characteristics which may discriminate between the mucosal and peripheral repertoire in the normal mucosa and in UC. PATIENTS: Blood and normal and diseased mucosa from two patients with UC were studied. METHODS: Immunoglobulin gene analysis and clone specific polymerase chain reaction were used to study the clonal distribution and characteristics of IgG and related IgA in the mucosa and blood of patients with UC. RESULTS: The IgG response in the mucosa of UC patients included widespread clones of cells that were present in both the diseased mucosa and blood but that were scarce in normal mucosa. Clonally related IgA class switch variants, all IgA1, were detected but also only in the diseased mucosa and blood. This suggests that these clones home preferentially to the diseased mucosa. We showed that J(H)1 usage was characteristic of the peripheral repertoire, and that examples of J(H)1 usage were observed in mucosal IgG in UC. CONCLUSIONS: Overall, these data are consistent with a model of UC in which a peripheral response is expressed and expanded in the colonic mucosa.