Functional morphology of the human endolymphatic sac. A review.

Modern immunohistochemical methods allow a functional characterization of the human endolymphatic sac (ES) and its associated cell populations. The currently available immunohistochemical data on the extraosseous part of the human ES support the assumption that the epithelium is metabolically active and capable of both secretion and absorption. The reactivity of some epithelial cells with antibodies against neuroendocrine antigens implies a paracrine activity of the human ES. Further results provide evidence for a possible role of the human ES in inner ear immune defense and indicate a putative functional relationship of the human ES to the common mucosa-associated immune system

Human endolymphatic sac: evidence for a role in inner ear immune defence.

In an immunohistochemical study, monoclonal and polyclonal antibodies have been used to identify cells and structures in the extraosseous part of endolymphatic sacs (ES) which were removed at autopsy from 30 persons. Intraluminal, intraepithelial, intravascular and perisaccular cells expressed the leukocyte common antigen. Immunostaining with antibodies against the CD4 and CD8 antigens revealed the predominance of CD4-positive T lymphocytes in the ES. A few lymphoid cells were found to express the major histocompatibility antigen class II. Interdigitating cells of the Langerhans type were rarely found in the epithelial layer. B lymphocytes were present in the lumen and the stroma of the ES and IgA- or IgG-containing cells in the stroma only. IgA, secretory component and the J chain were detected within epithelial cells and in the lumen of the ES. Macrophages were observed in the lumen and the stroma. Our findings are in accordance with previously published data in animals and man and give further evidence of an important role of the ES in inner ear immune defence

The intestinal immune system and its relation to disease.

The essential protective structure against the heavy enteric antigenic burden, the gut mucosa, prevents penetration of noxious agents, but allows a minimal exchange of large molecules and particles between the gut lumen and the 'milieu intérieur' of the body. M cells in the follicle-associated epithelium of the gut, ideal gateways for the presentation of enteric antigens to the cells of the gut-associated lymphoid tissue (GALT), are also weak links in the mucosal barrier, and may provide access for various microorganisms. The afferent limb of the GALT consists of distinct aggregates of lymphoid cells located in Peyer's patches, the vermiform appendix and the solitary lymphatic follicles, and of the mesenteric lymph nodes. The efferent limb subsumes the diffusely scattered mucosal leukocytes, mainly lymphocytes and plasma cells. Intraepithelial and mucosal T lymphocytes are instrumental in launching local immune responses, producing lymphokines, and in the specific lysis of virally infected cells. Antigenic stimulation of the GALT results in local secretion of antibodies, or in suppression of systemic immunologic responses to ingested antigens ('oral tolerance'). Poorly controlled mucosal immune responses result in organ-specific diseases. Extranodal lymphomas that mimic structures of the GALT may arise on a background of inflammatory or immunologic (autoimmune) disorders

Spirochaetosis of the human rectum associated with an intraepithelial mast cell and IgE plasma cell response.

In two patients presenting with mild intestinal symptoms, rectal spirochaetosis was the only morphological abnormality diagnosed by light microscopy. A re-evaluation of the morphological changes using electron microscopy and immunohistochemistry showed certain unusual features: the microorganisms were observed within epithelial cells and in subepithelial macrophages; there were numerous partially degranulated intraepithelial mast cells; and there was a marked increase in the proportion of IgE plasma cells within the lamina propria. Mucosal penetration by the organisms may be responsible for the unusual immune response. In one patient, treatment with antibiotics eliminated the spirochaetes and resulted in a clinical improvement. Spirochaetes should not always be considered as harmless commensals in the colon

Normal colorectal mucosa exhibits sex- and segment-specific susceptibility to DNA methylation at the hMLH1 and MGMT promoters

Silencing of gene expression by aberrant cytosine methylation is a prominent feature of human tumors, including colorectal cancers. Epigenetic changes of this type play undisputed roles in cell transformation when they involve genes that safeguard genome stability, and they can also be detected in precancerous lesions and seemingly normal peritumoral tissues. We explored physiological conditions associated with aberrant promoter methylation involving two DNA-repair genes in normal colorectal mucosa. Samples of cecal, transverse colon, sigmoid and rectal mucosa collected from 100 healthy individuals undergoing screening colonoscopy were analysed for hMLH1 and MGMT promoter methylation with a quantitative PCR assay. Positivity in at least one colon segment was common in both sexes, with methylation involving 0.1-18.8% of the alleles (median=0.49%). Samples from males showed no consistent patterns for either promoter, but there were striking age- and colon segment-specific differences in the female subgroup. Here, the prevalence of hMLH1 and MGMT methylation increased significantly with age, particularly in the right colon, where there was also an age-related increase in the percentage of alleles showing hMLH1 methylation. Concomitant methylation of both promoters was also significantly more common in the right colon of women. These findings paralleled immunohistochemical patterns of hMLH1 and MGMT protein loss in an independent series of 231 colorectal cancers and were consistent with current epigenetic profiles of colorectal cancer subsets. They suggest the intriguing possibility that the epigenetic signatures of cancers may have early-stage, normal-tissue counterparts that reflect potentially important aspects of the initial carcinogenetic process