Proliferative kinetics of large and small intraepithelial lymphocytes in the small intestine of the mouse

Porosity of the epithelial basement membrane as an indicator of macrophage-enterocyte interaction in the intestinal mucosa

The epithelial basement membrane of intestinal villi is perforated with numerous small pores, through which free cells in the lamina propria communicate with the enterocytes. This study was a comparative analysis of the pores in the basement membrane by SEM after removal of the gut epithelium with OsO4 maceration. The porosity as represented by the area fraction of the pores varied along the baso-apical axis of villi in patterns specific for each animal species examined: consistent scantiness along the entire length of villi in mice, acute elevation in the second and third distal one-sixths of villi in rats, and gradual augmentation toward the villus tips in guinea pigs. Size distribution analyses of the pores indicated their heterogeneous enlargement in the regions of elevated porosity. Concomitant observation of lamina propria macrophages by histochemical labelings and by conventional TEM showed that the cells specifically clustered beneath the hyperporous basement membrane, with their thick processes penetrating it. The spatially-regulated patterns of perforation of the epithelial basement membrane indicate phase-specific interventions of lamina propria macrophages in the maturation or aging of enterocytes, which steadily proliferate in crypts and exfoliate at the villus tips.

Zoite migration during infection: parasite adaptation to host defences

The apicomplexan parasite Eimeria tenella has evolved a number of strategies for migration into different compartments of the intestinal tissue during its life cycle. These migration events are associated intricately with pathogenesis and are currently of great interest to coccidiologists. Using evidence from in vivo studies and recent work on the dynamics of gut cell turnover, Peter Daszak suggests that E. tenella zoite migration might be viewed as parasite evolutionary adaptation to evade the host innate immune responses (resistance) and deal with the complex, dynamic nature of gut epithelial tissue.

The biology and pathobiology of the intestinal intraepithelial lymphocyte: a review of the literature

Intraepithelial lymphocytes represent a population of lymphocytes situated in the epithelial layer of all mucosae. In this report their biological and pathobiological features, with emphasis on intestinal intraepithelial lymphocytes, are reviewed.

Functional and structural aspects of the epithelial lymphocyte, with implications for coeliac disease and tropical sprue

Epithelial lymphocytes comprise a compartmentalised and specialised population of presumed effector cells which, in general, express the surface phenotypes (Lyt-2+; OX2+; OKT8+) of suppressor/cytolytic (Ts/c) cells. Granular cells within this population (gEL) morphologically resemble the circulating large granular lymphocytes (LGL) which subserve spontaneous (NK) cytolytic activity. Recent in vitro results indicate that gEL can develop this function after prolonged in vitro culture; the relevance of this, in vivo, remains to be decided. EL also appear to be able to mediate ADCC with sIgA against enteric micro-organisms. This is the kind of integrated activity that might be anticipated from local immunocytes within the intestinal mucosa. Other recent work suggests that gEL are not precursors of mucosal mast cells. EL also appear to be capable of inducing Ia-like expression in surface and crypt enterocytes, a property enjoyed both by highly purified Th, but also Ts/c, cells as well. This raises the interesting prospect that enterocytes may display antigen in macrophage-like fashion to other adjacent cells within the inter-epithelial cell spaces. These latter observations might be more consistent with the presence of 'activated' and 'blast-transformed' lymphocytes in such conditions as coeliac disease and tropical sprue. Another emergent view that demands appropriate attention is that the infiltrate of Ts/c cells into surface, and crypt, epithelium of coeliac mucosa does not necessarily cause injury or damage to the jejunal tissues. Nevertheless the role, either primary or secondary, that EL play either in coeliac disease or tropical sprue still remains obscure.

Isolation of murine small bowel intraepithelial lymphocytes

A method for the preparation of cellular suspensions of the epithelium of murine small bowel for the purpose of isolation and recovery of intraepithelial lymphocytes employing intraluminal hyaluronidase digestion is described. Discontinuous Percoll centrifugation of these suspensions yielded a 76-82% pure population of intraepithelial lymphocytes. Between 1.6 and 4.0 X 10(7) viable intraepithelial lymphocytes were obtained per gram of gut. The isolate contained approximately equal numbers of T, B and null lymphocytes.

Ultrastructure of gut-associated lymphoid tissue (GALT) in the amphibian urodele, Pleurodeles waltlii

The ultrastructure of gut-associated lymphoid tissue (GALT) has been studied in the salamander, Pleurodeles waltlii. Lymphoid accumulations appear as true infiltrates scattered throughout the lamina propria cell elements. The most important components of these infiltrates are small and medium sized lymphocytes, and, in lesser amounts, developing and mature plasma cells, macrophages and granulocytes. Migrating lymphoid cells massively invade the intestinal epithelium inducing noticeable modifications, such as the disappearance of the basement membrane and decreased numbers of mucous cells. Thus, in its organization and cell composition, the GALT of P. waltlii appears to represent a primitive phylogenetic precursor of the mammalian "intestinal-immunologic" barrier.

Epithelial and interepithelial mitoses of the oral mucosa: light and electron microscopic study in mice after exposure to different antigens

Many epithelia respond to exogenous injurious agents with an increased proliferation. Until now interepithelial cells (neuroectodermal cells, lymphocytes, cerebriform cells and Langerhans cells) have been neglected in investigations of the proliferation kinetics of stratified squamous epithelia. In mice with different antigenic exposure, and in T-cell deficient nude mice mitoses in the oral epithelium were counted by light microscopy and the proportion of mitoses of interepithelial cells was determined by an additional ultrastructural analysis. NMRI mice raised in "germ-free" and "specific pathogen-free" environments exhibit decreased mitotic rates in lingual and buccal epithelia (16 mitoses per 1000 basal cells) when compared with mice raised in "normal" environments. NMRI mice exposed orally to Candida albicans exhibit increased mitotic rates in the same 2 epithelial sites (35 mitoses per 1000 basal cells after 2 days). Similar changes occur in athymic nude mice. The electron microscopic observations showed that most of the mitoses occurred among keratinocytes. Only sporadic mitoses of nonepithelial cells could be observed within the epithelium. However, these amounted to less than 5% of the total of mitoses. Our results show that for proliferation kinetic studies of squamous epithelia this low proportion of interepithelial mitoses may be negligible. Interepithelial cells apparently recruit mainly from migrating cells into the epithelium, while proliferation in situ plays a secondary role. As there are no signs of a transmigration of the epithelium by interepithelial cells they must be considered a recirculating cell population.

Lymphocyte positions in the dome epithelium of the rabbit appendix

The apico-basal distribution of lymphocytes within the epithelium covering the domes of lymphatic tissue in the wall of the rabbit appendix was investigated in single and serial sections stained either for general histology, for cytoplasmic basophilia and acidophilia, or for nonspecific esterase activity. From the base to the summit of a dome, four zones numbered proximo-distally 1-4 were distinguished. Epithelial cells migrate from base to summit, as indicated by mitotic figures in zone 1, the gradual change from cytoplasmic basophilia to acidophilia in zones 2 to 4, and visible extrusion of cells from zone 4 at the summit. Zone 1 was free of lymphocytes. Most of the lymphocytes in zone 2 were intercellular and randomly arranged, but a few in this zone were within tapered epithelial cells modified by a process extending basally to the basement membrane. Small numbers of these tapered epithelial cells also occurred in zone 3. The large clusters of ten to 12 lymphocytes that characterized zone 3 were intercellular and impinged the apical regions of epithelial cells. Serial sections at the level of the distal cluster of zone 3 showed lymphocytes located also more basally, and some of these lymphocytes appeared to be passing through the basement membrane back into the lymphoid tissue of the dome. Epithelium of zone 4 over the distal surface of a dome was largely free of lymphocytes. Apparently most infiltrating lymphocytes form intercellular clusters and then return to the subepithelial lymphatic tissue.

Interepithelial cells of the oral mucosa. Light and electron microscopic observations in germfree, specific pathogen-free and conventionalized mice

Interepithelial cells are found in all epithelia of the internal and external surfaces of the mammalian body. The regional differences of these interepithelial cells and their function are not completely known so far. The quantitative and qualitative changes of the interepithelial cell population were investigated in germfree, specific pathogen-free and conventionalized mice by light and electron microscopy. Germfree and specific pathogen-free animals did not show significant differences in the number of interepithelial cells. In the epithelium of the tongue a mean of 7.4 cells per 1000 basal cells is found. After conventionalization a significant increase to 14.4 interepithelial cells per 1000 basal cells is observed. The number of cells in the buccal epithelium is constantly about 20% higher than in the epithelium of the tongue. In the oral mucosa lymphocytes, cerebriform cells and Langerhans cells are an integral component of the epithelium. In contrast to the monostratified intestinal mucosal epithelium, which is considered a secondary lymphatic tissue, the interepithelial lymphocytes of the oral mucosa are not significantly decreased in germfree animals. This could indicate that the oral mucosa functions partly as a primary lymphatic tissue. Interepithelial cerebriform cells and Langerhans cells increased after conventionalization with a maximum after 10 days in response to exogenous antigens. Both cells are immunologically important. The observations prove that the oral mucosa represents a local immunologic system in which the Langerhans cells plays an important part by formation a reticulo-epithelial tissue.

Organ culture of adult mouse intestine. I. Morphological results after 24 and 48 hours of culture

Explants of adult mouse intestine have been maintained in organ culture for 24 to 48 hr. The best results have been obtained with a mixture of DMEM-HEPES medium and NCTC-135 enriched with 10% fetal bovine serum. The morphology of the mucosa is well preserved at the light and electron microscopic level: absorbing cells exhibit an increase in secondary lysosomes; goblet cells and Paneth cells remain active; numerous mitoses are observed in the crypts; and vigorous re-epithelization takes place on the margin of the explants.

Kinetics of intraepithelial lymphocytes in the small intestine of thymus-deprived mice and antigen-deprived mice

The kinetics of lymphoid cells within the epithelium of the small gut has been studied in various thymus-deprived mice and in antigen-deprived mice by the use of 3H-thymidine injections and radioautography. In thymus-deprived mice--including adult thymectomized, thymectomized and irradiated, neonatally thymectomized, and nude mice - and in germ-free mice decreased numbers of intraepithelial lymphocytes (IL) were found. On the other hand, the radioautographic results indicated that the remaining IL populations included both newly formed and long-lived lymphoid cells in the same percentages as found in sham-operated controls and normal mice. It is concluded that although the presence of the thymus and the antigen content of the gut is of importance to the maintenance of the numbers of cells in the lymphoid populations of the intestinal wall, the basic kinetics of these cell populations are preserved in deprived mice.