Kinetics of cell population of the jejunal mucosal epithelium in mice after administration of syngeneic lymphocytes

By means of the radioautographic method the state of cellular restoration of the gastric epithelium has been estimated after administration of syngenic lymphocytes to mice. Under conditions of physiological regeneration T-lymphocytes are able to inhibit proliferation of the epithelial cells and to limit the size of the proliferation zone in crypts. The inhibition degree of the proliferative activity depends on the doze of the T-cells administered. In order to demonstrate their activity, T-cells do not need DNA and RNA synthesis de novo. At the same time, protein synthesis is necessary; it occurs on long-living mRNA lymphocytes. The T-lymphocyte action is reversible at the tissue, but not at the cellular level. The mechanism of decreasing cell reproduction under effect of T-lymphocytes is described. In the process of lymphoid regulation of the cellular restoration in the intestinal epithelium changes in the size of the proliferative pool play the main role.     

Dose-response relationships for chromosome aberrations in peripheral blood lymphocytes after whole- and partial-body irradiations: II. Decline of aberration-carrying cells in blood with time post-exposure

Dicentric yield and fractionation of damaged metaphases and lymphocyte count were followed for an interval of up to 3 months in rabbits after partial- and whole-body irradiations.Some partial-body exposures led to less-pronounced decline of the lymphocyte count in peripheral blood than others; in the former case the reduction of dicentric yield in peripheral blood lymphocytes over the first 24 h post exposure was significantly faster than in the latter. The decline was also faster than after uniform whole-body irradiation where it was virtually absent. However, the results suggest that, after whole-body exposures, the decline of the fraction of damaged metaphases with post-exposure time was much slower than that of the dicentric yield.     

Homeobox gene expression in the intestinal epithelium of adult mice.

Using a polymerase chain reaction-based strategy, we have detected the expression of nine different homeobox genes in adult mouse intestine. Included among these are the recently described intestine-specific Cdx-1 gene and a new, related gene, Cdx-2. Southern blot experiments show that Cdx-2 is present in a single copy in the mouse genome. Of several adult mouse tissues assayed, intestine was the only one that contained detectable levels of Cdx-2 mRNA. Expression of all nine homeobox genes in different regions of the intestine was quantitated by RNase protection analysis, which revealed a unique expression profile for each gene. These observations suggest that homeobox gene expression may play an important role in cellular differentiation in the adult intestine.     

Self-reactive, T cell receptor-gamma delta+, lymphocytes from the intestinal epithelium of weanling mice.

Intraepithelial T lymphocytes (IEL) are dispersed throughout the intestinal epithelial lining but their role in cellular immune defense is unknown. Their location suggests that their highly activated state may be due to constant exposure to bacterial Ag. To study IEL specificity and function we have prepared a panel of IEL-T cell hybridomas from both adult and weanling C57B1/6 mice. Many of these expressed TCR-gamma delta, a cell type rare in peripheral lymph nodes and spleen but predominant at epithelial surfaces. We have identified a subset of gamma delta T cells from weanling mice which is self reactive, i.e., these hybrids secrete IL-2 spontaneously, without antigenic stimulation or a requirement for APC. Self-reactive TCR-gamma delta+ hybrids and lines, all of which bear a particular TCR (V gamma 1.1C gamma 4V delta 6), have previously been derived from neonatal thymus and the skin. Northern blot and immunoprecipitation analyses suggest that the self-reactive IEL hybrids also bear a C gamma 4/V delta 6 TCR. Antibody inhibition experiments showed that the self-reactivity of the IEL hybrids is TCR mediated. Spontaneous IL-2 production was blocked by soluble anti-CD3 and anti-TCR-gamma delta antibodies but not by antibodies to the TCR-alpha beta. The self-reactive IEL hybrids lack class II MHC and the class I-like proteins CD1 and TLA but express class I MHC. IEL hybrids may also require the vitronectin receptor as an accessory molecule for their activation because spontaneous IL-2 production is blocked by antibody to the vitronectin receptor as well as by the extracellular matrix protein active site peptide RGDS, but not the control peptide RGES. V gamma 1.1C gamma 4V delta 6 T cells in the thymus, skin, and intestine may represent a small and unique subpopulation of lymphocytes with a potential for autoimmune reactivity at peripheral sites.     

The response of the intestinal epithelium in B10.A mice to infection with Trichinella spiralis

Previous studies on intestinal trichinosis have dealt mainly with areas other than the intestinal epithelium. Since the epithelium is now known to be the parasite's habitat, its response to infection is important. Infection with Trichinella spiralis in immunologically slow-responding B10.A mice was associated with crypt hyperplasia and villus atrophy. With similar infection levels in both primary and challenge infections, there was no difference in the maximal degree of atrophy or hyperplasia between the 2 groups. However, challenged mice underwent these mucosal changes in about half the time. Expulsion of worms always occurred during regeneration of the intestinal epithelium suggesting that the host's defense mechanism of altering the kinetics of the epithelium was not the prime factor causing expulsion. Pulse labelling of enterocytes with [3H] thymidine showed that there was no significant increase in the relative size of the proliferation zone. This indicates that the crypt cell output was not altered by this parasite. Atrophy of the villus was analysed with respect to its 3-dimensional shape. There was a decrease in both height and width of the villus but not thickness. Thus, there is a real decrease in the size of the enterocyte population per villus. Histochemical staining of the enterocyte brush border by an alkaline phosphatase method showed that (1) hyperplastic crypts have an enlarged maturation zone and (2) the villus epithelium is composed entirely of mature cells. The distribution of the nematode population was compared to these changes in the intestine. Trichinella spiralis showed a marked anteriad (distal to proximal) migration prior to expulsion. Thus, utilizing a novel approach to study intestinal trichinosis, the response of the mucosal epithelium has been characterized.     

The effects of myeloablative or non-myeloablative total body irradiations on intestinal tract in mice

Acute radiation injury caused by high-dose radiation exposure severely impedes the application of radiotherapy in cancer management. To deeply understand the side effects of radiation on intestinal tract, an irradiation murine model was applied and evaluated. C57BL/6 mice were given 4 Gy non-myeloablative irradiation, 8 Gy myeloablative irradiation and non-irradiation (control), respectively. Results demonstrated that the 8 Gy myeloablative irradiations significantly damaged the gut barrier along with decreasing MECA32 and ZO-1. However, a slight increase in MECA32 and ZO-1 was detected in the 4 Gy non-myeloablative irradiations treatment from day 5 to day 10. Further, the irradiations affected the expression of P38 and JNK mitogen-activated protein kinase (MAPK) but not ERK1/2 MAPK signal pathway. Moreover, irradiation had adverse effects on hematopoietic system, altered the numbers and percentages of intestinal inflammatory cells. The IL-17/AhR had big increase in the gut of 4 Gy irradiation mice at day 10 compared with other groups. Both 8 Gy myeloablative and 4 Gy non-myeloablative irradiation disturbed the levels of short-chain fatty acids (SCFAs) in intestine. Meanwhile, high dosage of irradiation decreased the intestinal bacterial diversity and altered the community composition. Importantly, the fatty acids generating bacteria Bacteroidaceae and Ruminococcaceae played key roles in community distribution and SCFAs metabolism after irradiation. Collectively, the irradiation induced gut barrier damage with dosages dependent that led to the decreased p38 MAPK and increased JNK MAPK, unbalanced the mononuclear cells (MNCs) of gut, disturbed intestinal bacterial community and SCFAs level.