Regional variations in the distribution of small intestinal intraepithelial lymphocytes in three inbred strains of mice

Age-dependent changes in intraepithelial lymphocytes (IELs) of the small intestine, cecum, and colon from young adult to aged mice

We previously reported the regional differences in the IELs present in the proximal (P), middle (M), and distal (D) parts of the small intestine, cecum (Ce), and colon (Co) of mice. In this study, we investigated the age-dependent changes in the regional differences of IELs from young adult to aged mice. In this experiment, 3-, 6-, 12-, 18-, and 24-month-old mice were examined. IELs were separately isolated from 5 parts of the intestines and analyzed by flow cytometry. Regional differences in the number and phenotype of IELs showed the same trends in all age groups. The number of IELs was highest in 6-month-old mice and then gradually decreased with age. As to IEL subsets, age-related changes were not seen except for a few subsets among the age groups. We conclude that age-related decreases in IELs in mouse small intestine may be one of the aging phenomena of the intestinal immune system. Such age-related decreases in IELs may be concerned with the increased liability to intestinal infections in the elderly.

TL and CD8αα: Enigmatic partners in mucosal immunity

The intestinal mucosa represents a large surface area that is in contact with an immense antigenic load. The immune system associated with the intestinal mucosa needs to distinguish between innocuous food antigens, commensal microorganisms, and pathogenic microorganisms, without triggering an exaggerated immune response that may lead to excessive inflammation and/or development of inflammatory bowel disease. The thymus leukemia (TL) antigen and CD8αα are interacting surface molecules that are expressed at the frontline of the mucosal immune system: TL is expressed in intestinal epithelial cells (IEC) whereas CD8αα is expressed in lymphocytes, known as intraepithelial lymphocytes, that reside in between the IEC. In this review we discuss the significance of the interaction between TL and CD8αα in mucosal immunity during health and disease.

Differences in intraepithelial lymphocytes in the proximal, middle, distal parts of small intestine, cecum, and colon of mice

We have previously reported the regional differences in the intraepithelial lymphocytes (IELs) present in the small intestine of mice. In this study, we further investigated these differences on the basis of our previous findings and studied the entire intestine, including the cecum and colon. Most of the significant differences in phenotypic compositions were found between the small and large intestines, although some differences were found among the different parts of the small and large intestines. In particular, the composition of the subsets in alphabeta T cells and gammadelta T cells clearly differed between the small and large intestines. For example, in alphabeta T cells, the percentages of double negative (DN) and CD8alphaalpha(+) cells were higher in the large intestine, that of CD8alphabeta(+) cells was higher in the small intestine, and those of CD4(+) and CD4(+) CD8alphaalpha(+) double positive (DP) cells were higher in the distal part of the small intestine. In gammadelta T cells, the percentage of CD8alphaalpha(+) cells was higher in the small intestine and that of DN cells was higher in the large intestine. These results indicate that the differences between IELs in the small and large intestines are discontinuous.

Regionalization of pIgR expression in the mucosa of mouse small intestine

Few reports exist on the differences in cell populations or immunological functions between the proximal and distal segments of the small intestine (SI). In the current contribution we analyzed the expression of the polymeric immunoglobulin receptor (pIgR) and alpha chains as well as the density of IgA-producing cells from the proximal and distal intestinal segments from Balb/c mice. Furthermore, by using real-time RT-PCR we quantified the expression of cytokines (TNF-alpha, IFN-gamma, IL-4 and TGF-beta), Toll-like receptor-4 (TLR-4), and the glucocorticoid receptor (GR) involved in pIgR expression in intestinal epithelial cells (IEC). In this study, for the first time it has been demonstrated that the expression of the pIgR as well as alpha chain was greater in the proximal than the distal segment of the small intestine of normal mice. Moreover, we found striking differences in the expression of cytokines at the different intestinal compartments. Whereas the expression of TNF-alpha, IFN-gamma and TGF-beta was higher in lamina propria lymphocytes (LPL) of the distal than proximal segment, it was higher in IEC of the proximal than distal segment. In contrast, the expression of the gene for IL-4 was higher in the LPL of the proximal segment and the IEC of the distal segment. Although the overall expression of TNF-alpha, IL-4, IFN-gamma and TGF-beta was higher in the whole mucosa of the distal than proximal segment, we propose that cytokines produced by epithelial cells (TNF-alpha, IFN-gamma and TGF-beta) autocrinally up-regulate the expression of mRNA for the pIgR. Finally the expression of the GR was higher in the proximal segment, while the expression of the gene for TLR-4 was significantly higher in the IEC of the distal than proximal segment. The higher expression of pIgR found in the proximal segment is probably related to the effect on epithelial cells of the higher production of TNF-alpha, IFN-gamma and TGF-beta, as well as the higher expression of the glucocorticoid receptors. The increased expression of pIgR in the proximal segment appears primarily responsible for the increased secretory IgA levels in the small intestine of mice. These results confirm and extend previous findings supporting the compartmentalization of the intestinal immune system.

Effect of restraint stress on the population of intestinal intraepithelial lymphocytes in mice

The impact of restraint stress on the intestinal immune system, particularly on intestinal intraepithelial lymphocytes (i-IEL), has not been described in detail. Thus, the purpose of this study was to assess the effects of restraint stress, including those produced by increases in glucocorticoids and catecholamines, on the population of i-IEL. Mice were exposed to 1 or 4h restraint stress for 4 day, and the number of IEL in the mucosa of the proximal small intestine was determined by immunohistochemistry. The effects of restraint were also analyzed in mice submitted to different procedures: adrenalectomy, chemical sympathectomy, and treatment with a glucocorticoid antagonist (RU486), dexamethasone, and epinephrine. The main findings were that: (1) chronic restraint-stress reduced the i-IEl population in the small intestine; (2) adrenalectomy, treatment with RU-486 and chemical sympathectomy decreased the number of gammadelta, CD4+ and CD8+ T cells in non-stressed groups; (3) dexamethasone reduced the number of gammadelta and CD8+ T cells, and (4) epinephrine reduced the number of gammadelta, CD4+ and CD8+ T cells. These results demonstrated that restraint stress decreased the number of i-IEL in the proximal small intestine of mice, mainly by the combined action of higher concentrations of catecholamines and glucocorticoids, and that lower concentrations of glucocorticoids and catecholamines in unstressed mice preserved the population of i-IEL.

Influences of orally administered lactoferrin on IFN-γ and IL-10 production by intestinal intraepithelial lymphocytes and mesenteric lymph-node cellsThis paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal's usual peer review process

Intestinal mucosal immunity plays an important role in mucosal and systemic immune responses. We investigated the influences of orally administered bovine lactoferrin (LF) on cytokine production by intestinal intraepithelial lymphocytes (IEL) and mesenteric lymph-node (MLN) cells, especially T cells. Bovine LF or bovine serum albumin (control) was administered to mice once daily for 3 d. After 24 h from the last administration, IEL of the jejunum and ileum and MLN cells were isolated. These cells were cultured with and without the anti-T-cell-receptor antibody, and then the culture supernatants were assayed for cytokines with ELISA. Oral LF did not affect the ratio of T-cell subpopulations in IEL and MLN; however, LF enhanced both interferon (IFN)-γ and interleukin (IL)-10 production by unstimulated IEL and by IEL stimulated with the αβ T-cell receptor but not with the γδ T-cell receptor. LF also enhanced both IFN-γ and IL-10 production by stimulated and unstimulated MLN cells. The production level of IFN-γ by MLN cells was correlated with that of IL-10. These results suggest that oral LF enhances the production of both Th1-type and Th2/Tr-type cytokines in the small intestine of healthy animals.

Regional variations in the distributions of small intestinal intraepithelial lymphocytes (IELs) in outbred laboratory mice (Mus musculus domesticus) and the inbred strain of mice established from Japanese fancy mice (Mus musculus molossinus)

Previously, we reported regional variations in small intestinal IELs of mice. In this study, we examined the regional variations of IELs in outbred laboratory mice (ddY: Mus musculus domesticus) and the inbred strain of mice established from Japanese fancy mice (JF1: Mus musculus molossinus). IELs were isolated from the proximal, middle and distal parts of the small intestine and analyzed by flow cytometry. The percentages of gammadelta T cells and alphabeta T cell subset of extrathymic origin were higher in the proximal part while the percentages of alphabeta T cell subset(s) of thymic origin were higher in the distal part in both ddY and JF1 mice. Such trends in regional variations of IELs were almost the same as those found in the inbred strains of laboratory mice in our previous reports. This strongly suggests that these regional variations of IELs may be common phenomena in Mus musculus species.

IELs: enforcing law and order in the court of the intestinal epithelium

The intestinal intraepithelial lymphocytes (IELs) are mostly T cells dispersed as single cells within the epithelial cell layer that surrounds the intestinal lumen. IELs are, therefore, strategically located at the interface between the antigen-rich outside world and the sterile core of the body. The intestine of higher vertebrates has further evolved to harbor numerous commensal bacteria that carry out important functions for the host, and while defensive immunity can effectively protect against the invasion of pathogens, similar immune reactions against food-derived antigens or harmless colonizing bacteria can result in unnecessary and sometimes damaging immune responses. Probably as a result of this unique dilemma imposed by the gut environment, multiple subsets of IEL have differentiated, which all display characteristics of 'activated yet resting' immune cells. Despite this common feature, IELs are heterogeneous with regard to their phenotype, ontogeny, and function. In this review, we discuss the different subtypes of IELs and highlight the distinct pathways they took that led to their unique differentiation into highly specialized effector memory T cells, which provide the most effective immune protection yet in a strictly regulated fashion to preserve the integrity and vital functions of the intestinal mucosal epithelium.

Age-related changes in the regional variations in the number and subsets of intraepithelial lymphocytes in mouse small intestine

Previously, we reported regional variations in the number and subsets of the small intestinal IELs of mice. In this study, we examined the age-related changes in the regional variations of IELs in mice from 2 to 11 weeks old. IELs were isolated from the proximal, middle and distal parts of the small intestine and analysed by flow cytometry. The total number of IELs gradually increased with age and reached a plateau at 8 weeks old. As to IEL subsets, the percentage of alpha beta T cells was higher in the distal part at and after 2 weeks of age (before weaning). The percentage of the alpha beta T cell subset of extrathymic origin was higher in the proximal part while the percentages of alpha beta T cell subsets of thymic origin were higher in the distal part at and after 3 weeks (just after weaning). It appears that regional variations in IELs may be formed before the weaning period in mice.

Regional variations in the distributions of small intestinal intraepithelial lymphocytes in germ-free and specific pathogen-free mice

Previously, we reported the regional variations in intraepithelial lymphocytes (IELs) in the small intestine of mice. To clarify the effects of intestinal bacteria on the distribution of IELs, regional variations in IELs were examined using germ-free (GF) and specific pathogen-free (SPF) BALB/cA mice. The small intestine was taken and divided equally into three parts (the proximal, middle, and distal parts). IELs were isolated from each part of the intestine, and the total number of IELs in GF mice was about one seventh of that in SPF mice. The decreased number of IELs in GF mice suggests that intestinal bacteria may be essential for local expansion of IELs. On the other hand, similar regional variations in IEL subsets observed in both GF and SPF mice, except for some subsets. The similarity of regional variations in GF and SPF mice indicates that the regional variations in IEL subsets may not fundamentally depend on intestinal bacteria.

Regional variations in the distribution of small intestinal intraepithelial lymphocytes in alymphoplasia (aly/aly) mice and heterozygous (aly/+) mice

Regional variations in intraepithelial lymphocytes (IELs) in the small intestine were examined in alymphoplasia mutant (aly/aly) mice, which are characterized by the systemic absence of lymph nodes and Peyer's patches, and heterozygous (aly/+) mice. The small intestines were taken from 10 to 12-week-old mice and divided equally into 3 parts (the proximal, middle and distal parts). IELs were isolated from each part of the intestine and analyzed with a flow cytometer. The number of IELs in the distal part was significantly fewer in aly/aly mice compared with aly/+ mice, although the total number of small intestinal IELs were comparable between them. As to the IELs subsets, regional variations in alphabeta T cells and gammadelta T cells were observed in aly/+ mice, but they disappeared in aly/aly mice. However, regional variations in composition of alphabeta T cell subsets were similarly observed in both aly/aly mice and aly/+ mice. This indicates that, although not essential, mesenteric lymph nodes (MLN) and/or Peyer's patches may modify the regional variations in IELs.

Murine female reproductive tract intraepithelial lymphocytes display selection characteristics distinct from both peripheral and other mucosal T cells

Despite immense effort, the development of vaccines effective at mucosal sites has proceeded at a faltering pace. Efforts concentrating on humoral immunity but neglecting cellular immunity may be misdirected by ignoring many viral mucosal pathogens. Improved understanding of the development and maintenance of lymphocytes populating the reproductive tract (rtIELs) may inform advances in vaccination strategies for sexually transmitted diseases. Recent studies highlight tissue-specific differences in the development of mucosal immunity and suggest that the local milieu may play a role in selection, maintenance and function of resident lymphocytes. Here, we describe MHC class I and thymus dependence of subpopulations of rtIELs. TCRalphabeta+ CD8alphabeta+ T cells in the periphery, intestine, and female reproductive tract are all developmentally dependent on classical class I MHC and the thymus. TCRalphabeta+ CD8alphaalpha+ are absent from the periphery and the rtIELs, but are present and classical MHC class I-independent, in the intestine. In contrast to intestinal TCRgammadelta+ cells, TCRgammadelta+ rtIELs are CD8 negative and thymus dependent. In contrast to peripheral TCRgammadelta+ cells, murine TCRgammadelta+ rtIELs express not a diverse array of Vdelta genes, but rather, a canonical Vdelta1. In summary, lymphocytes isolated from the murine female reproductive tract have characteristics distinct from both peripheral T cells and those found at other mucosal sites. Therefore, for the purpose of vaccination strategies, the female reproductive tract should be regarded neither as peripheral nor mucosal, but rather as a tissue with distinctive immunological characteristics.