An atypical population of NK cells that spontaneously secrete IFN-gamma and IL-4 is present in the intraepithelial lymphoid compartment of the rat

The suckling rat as a model for immunonutrition studies in early life

Diet plays a crucial role in maintaining optimal immune function. Research demonstrates the immunomodulatory properties and mechanisms of particular nutrients; however, these aspects are studied less in early life, when diet may exert an important role in the immune development of the neonate. Besides the limited data from epidemiological and human interventional trials in early life, animal models hold the key to increase the current knowledge about this interaction in this particular period. This paper reports the potential of the suckling rat as a model for immunonutrition studies in early life. In particular, it describes the main changes in the systemic and mucosal immune system development during rat suckling and allows some of these elements to be established as target biomarkers for studying the influence of particular nutrients. Different approaches to evaluate these immune effects, including the manipulation of the maternal diet during gestation and/or lactation or feeding the nutrient directly to the pups, are also described in detail. In summary, this paper provides investigators with useful tools for better designing experimental approaches focused on nutrition in early life for programming and immune development by using the suckling rat as a model.

Intestinal intraepithelial NK and NKT cell ontogeny in Lewis rats

Natural killer T (NKT) cells have been described in the liver and spleen of adult rats, but their presence and function in other tissues and in early life remains uncertain. This study was designed to determine the proportion of NK cells and NKT cells among small intestine intraepithelial (IE) lymphocytes in suckling rats and adult animals by flow cytometry. Very few intestinal IE-NKT cells (NKR-P1A+ TCRalphabeta+) were present in adult rats ( approximately 1%), but a high proportion of this population was found during early life ( approximately 40% of IE lymphocytes in 9-day-old rats), with a marked age-decreasing pattern. Most of these cells presented the CD8alphabeta+ phenotype. Intestinal IE-NK cells (NKR-P1A+ TCRalphabeta-) were also present in a relatively high proportion during the suckling period ( approximately 30% of IE lymphocytes). Thus, a predominance of both NK and NKT cell subpopulations in small intestine epithelium is characteristic in the early life of rats and may have a protective role during the suckling period.

Bovine whey protein concentrate supplementation modulates maturation of immune system in suckling rats

During neonatal life, challenges from breast milk and microbial flora promote immune system maturation. Immunonutrition in these stages may become an important way to increase natural defence systems. The aim of this study was to determine the effect of a daily bovine milk whey protein concentrate (WPC) supplement on the intestinal and systemic immune systems in suckling rats. The composition of intraepithelial and lamina propria lymphocytes (IEL and LPL) was analysed by flow cytometry. Systemic and intestinal humoral immune responses were determined by sera Ig levels and Ig-secreting cell quantification by ELISA and ELISPOT, respectively. From birth, suckling Wistar rats were supplemented with WPC or standard infant formula (SIF). The WPC group showed the same proportion of most of the main mucosal cell subsets as the reference animals. However, in the first days of life WPC enhanced the innate immunity by increasing the NK cell proportion in both epithelial and lamina propria (LP) compartments. A rise in intestinal CD8alphaalpha+ IEL was also induced by WPC supplementation. A time-course of sera Ig levels and spontaneous IgA, IgM and IgG production by LPL and mononuclear cells from blood and spleen, in the WPC group, exhibited a similar pattern to those pups fed only by dam's milk. In summary, the present results show the effects of WPC on enhancing mucosal innate immunity during early life.

Modulation of mucosal immunity in a murine model of food-induced intestinal inflammation

BACKGROUND

Hypersensitivity or uncontrolled responses against dietary antigens can lead to inflammatory disorders like food allergy and current models reflect a variety of causes but do not reveal the detailed modulation of gut immunity in response to food antigens after breakdown in mucosal tolerance.

OBJECTIVE

To develop and characterize a murine model for food-induced intestinal inflammation and to demonstrate the modulation of gut immune response by dietary allergenic antigens.

METHODS

C57BL/6 mice were sensitized with peanut proteins, challenged with peanut seeds and their sera and gut segments were collected for subsequent analyses.

RESULTS

Sensitization and challenged with peanut seeds led to alterations in gut architecture with inflammatory response characterized by oedema in lamina propria and cell infiltrate composed mainly by eosinophils, mast cells, phagocytes, natural killer and plasma cells, together with low percentage of gammadelta+ and CD4+CD25+Foxp3+ cells in Peyer's patches. These animals also presented high levels of specific IgE and IgG1 in sera and modulation of mucosal immunity was mediated by increased expression of GATA-3, IL-4, IL-13 and TNF-alpha in contrast to low IFN-gamma in the gut.

CONCLUSION

A murine model for food-induced intestinal inflammation was characterized in which modulation of gut immunity occurs by peanut antigens in consequence of T-helper type 2 (Th2) allergic response and failure of regulatory mechanisms necessary for mucosa homeostasis, resembling food allergy. This work shed some light on the understanding of the pathogenesis of gastrointestinal disorders and intolerance in the gut and supports the development of therapies for food-related enteropathies like food allergy, focusing on gut-specific immune response.

Dietary glutamine affects mucosal functions in rats with mild DSS-induced colitis

The development of inflammatory bowel disease may involve immune dysfunction. Because enteral glutamine is the main source of amino acids for the intestinal mucosa and is metabolized at high rates by both enterocytes and immunocytes, the aim of this study was to ascertain the protective role of glutamine supplementation in a DSS-induced model of mild experimental colitis on metabolic, immune, and intestinal variables. Lewis rats were fed diets supplemented with glutamine (glutamine diet, G group) or an isoenergetic isonitrogenous control diet (C group) from postnatal d 21 (weaning) and continuing to d 35. On d 30, half of the rats from both groups were given 0.5% DSS in drinking water (G-DSS and C-DSS groups). Glutamine supplementation increased the plasma concentrations of Thr, Gln, Cit, His, and Arg and enhanced the ratio of essential to nonessential amino acids irrespective of DSS treatment. DSS administration increased the plasma Gln concentration, indicating a reduced utilization of this amino acid by the intestinal tissue. Regarding the gut-associated lymphoid tissue lymphocyte populations, DSS increased the percentages of CD3(+) T lymphocytes from Peyer's patches, NK and B lymphocytes from mesenteric lymph nodes, and NK CD8(-) cells from intraepithelial lymphocytes. The administration of glutamine did not affect the inductive populations nor did it modify T-cell subtypes or the percentage of intraepithelial lymphocytes of gut-associated lymphoid tissue. However, glutamine supplementation reduced the feces water contents in the DSS-treated but not in the untreated rats. These results indicate that glutamine supplementation can improve barrier function in rats with colitis.

Developmental changes in intraepithelial T lymphocytes and NK cells in the small intestine of neonatal rats

The main objective of this study was to characterize developmental changes in small intestinal intraepithelial lymphocyte (IEL) subpopulations during the suckling period, thus contributing to the understanding of the development of diffuse gut-associated lymphoid tissue (GALT) and to the identification of early mechanisms that protect the neonate from the first contact with diet and gut microbial antigens. The study was performed by double labeling and flow cytometry in IEL isolated from the proximal and distal small intestine of 1- to 21-d-old Lewis rats. During the suckling period, intraepithelial natural killer (NK) cells changed from a typical systemic phenotype, CD8+, to a specific intestinal phenotype, CD8-. Analysis of CD8+ IEL revealed a progressive increase in the relative number of CD8+ IEL co-expressing TCRalphabeta, cells associated with acquired immunity, whereas the percentage of CD8+ cells expressing the NK receptor, i.e. cells committed to innate immunity, decreased. At weaning, IEL maturity was still not achieved, as revealed by a phenotypic pattern that differed from that of adult rats. Thus, late after weaning, the regulatory CD8+CD4+ T IEL population appeared and the NK population declined. In summary, the intestinal intraepithelial compartment undergoes changes in its lymphocyte composition associated with the first ingestion of food. These changes are focused on a relatively high proportion of NK cells during the suckling period, and after weaning, an expansion of the regulatory CD8+CD4+ T cells.

Novel insights on human NK cells' immunological modalities revealed by gene expression profiling

As part of the innate immune system, human NK cells play a critical role early in the systemic host defense against pathogens and tumor cells. Recent studies suggest a more complex view of NK cell behavior, as different functions and tissue localizing capabilities seem to be preferentially assigned to distinct subpopulations of NK cells, CD56(dim)CD16(+) or CD56(bright)CD16(-). In this study, we used oligonucleotide microarrays to compare the expression profile of approximately 20,000 genes in three NK cell subpopulations: peripheral blood-derived CD56(dim)CD16(+), CD56(bright)CD16(-), and in vitro-activated CD16(+) NK cells. The differential expression of selected genes was verified by flow cytometry and functional assays. When comparing CD56(dim)CD16(+) and CD56(bright)CD16(-) subsets, a new heterogeneous molecular basis for the functional and developmental differences between these two subsets was revealed. Furthermore, systematic analysis of transcriptional changes in activated CD16(+) NK cells provided us with a better understanding of NK function in inflamed tissues. We highlight a number of genes that were overexpressed upon activation (e.g., OX40 ligand, CD86, Tim3, galectins, etc.), that enable these cells to directly cross-talk with other innate and adaptive immune effectors. The overexpressed genes assign novel intriguing immunomodulatory functions to activated NK cells, in addition to their potent cytotoxic abilities.

Fermentable dietary fiber potentiates the localization of immune cells in the rat large intestinal crypts

Intestinal crypts are composed of a well-defined hierarchy of epithelial cells, and proliferating epithelial cells reside close to the bottom of the crypts-even in the large intestine. We investigated whether CD8(+)and CD4(+)intraepithelial lymphocytes (IELs) and CD161(+) natural killer (NK) cells localized in proliferating or differentiated epithelial region of cecum and colon. Both proliferating epithelial layer cells and the immune cells along the longitudinal crypt axis of the large intestine were measured histochemically. Dietary intervention revealed that the physiological localization of the immune cells in the longitudinal crypt axis depended on the immune cell type. CD8(+) IELs were preferentially located among differentiated epithelial cells. In contrast, CD161(+) NK cells were located adjacent to the epithelial cells at the bottom of crypt. Cecal crypts contained significantly larger numbers of CD8(+) IELs than did colonic crypts. However, there was only a minor population of CD4(+) IEL in the cecal and colonic epithelia. Some dietary fibers increased the densities of CD8(+) IELs and CD161(+) NK cells in the cecum, with the magnitude of response varying among the types of fiber. There was a significant relationship between SCFA and the localization of immune cells, especially CD8(+) IEL and CD161(+) NK cells, which are considered to be involved in the maintenance of epithelial homeostasis.

Deficiencies in gut NK cell number and function precede diabetes onset in BB rats

Defects in the intestinal immune system may contribute to the pathogenesis of autoimmune diseases. Intraepithelial lymphocytes represent a substantial fraction of gut-associated lymphocytes, but their function in mucosal immunity is unclear. A newly described population of NK cells that spontaneously secrete IL-4 and IFN-gamma is present in the intraepithelial lymphocyte compartment of the rat. We hypothesized that defects in the number or function of these cells would be present in rats susceptible to autoimmunity. We report that the number of NKR-P1A(+)CD3(-) intraepithelial NK (IENK) cells is deficient before onset of spontaneous autoimmune diabetes in diabetes-prone BB (BBDP) rats. The absolute number of recoverable IENK cells was only approximately 8% of that observed in WF rats. Bone marrow transplantation from histocompatible WF donors reversed the IENK cell deficiency (and prevented diabetes) in these animals, suggesting a hemopoietic origin for their IENK cell defect. Analysis of diabetes-resistant BB rats, which develop autoimmune diabetes only after perturbation of the immune system, revealed IENK cell numbers intermediate between that of BBDP and WF rats. IENK cells were selectively depleted during treatment to induce diabetes. Prediabetic BBDP and diabetes-resistant BB animals also exhibited defective IENK cell function, including decreased NK cell cytotoxicity and reduced secretion of IL-4 and IFN-gamma. IENK functional defects were also observed in LEW and BN rats, which are susceptible to induced autoimmunity, but not in WF, DA, or F344 rats, which are resistant. Defects in IENK cell number and function may contribute to the pathogenesis of autoimmune diseases including type 1 diabetes.

Divergence in NK cell and cyclic AMP regulation of T cell CD40L expression in asthmatic subjects

T cells are central in the pathogenesis of asthma, and the associated ligand, CD40L, plays an important role by increasing production of immunoglobulin E and inflammatory mediators. beta-Adrenoceptor agonists are commonly used in asthma, although little is known regarding effects on CD40L expression and T cell activation. Here, we demonstrate that cyclic adenosine monophosphate (cAMP) and beta-adrenoceptor agonists differentially regulate CD40L in asthma. cAMP increased naïve T cell CD40L expression in asthmatics (9.8+/-8.5 increase in percent CD40L-positive cells), and expression in control subjects was inhibited (7.1+/-6.0 decrease in percent CD40L-positive cells; P< 0.05). Cell depletion and reconstitution experiments were used to determine that cAMP enhancement of CD40L required cell-to-cell contact with an asthma-associated natural killer (NK) cell subset. The NK cell subset expressed elevated levels of CD95, and in vitro-generated CD95+ NK2 cells also produced similar effects on CD40L expression. Our findings suggest that a subset of NK cells with elevated CD95 expression is associated with asthma and can reverse cAMP inhibitory effects on T cell CD40L with the potential to increase disease exacerbation.

Human small-intestinal epithelium contains functional natural killer lymphocytes

BACKGROUND & AIMS

CD3(-) non-T lymphocytes constitute the second most abundant lymphoid subset in the human small-bowel epithelium, and these CD3(-) intraepithelial lymphocytes are virtually absent in active celiac disease. Phenotypically, they resemble natural killer cells and have been termed natural killer-like intraepithelial lymphocytes. Because of the limited availability of appropriate human samples, functional studies have not yet been reported, and it is not yet clear whether these are true natural killer cells.

METHODS

We used magnetic bead-based purification and flow cytometry to study several aspects of normal human small-bowel natural killer-like intraepithelial lymphocytes: intracellular cytokine content (basally and after activation); ability to lyse natural killer-sensitive K562 target cells; and expression of perforins, Fas ligand, and other functional markers.

RESULTS

CD3(-) intraepithelial lymphocytes cultured in interleukin-2 showed a higher lymphokine-activated killer activity than CD3(+) intraepithelial lymphocytes (48%-83% lysis exerted by CD3(-) intraepithelial lymphocytes at an effector-target cell ratio of 2:1 vs. 8%-18% by CD3(+) intraepithelial lymphocytes). Perforin content correlated with this lytic potential (75% +/- 4% in CD3(-) vs. 5% +/- 4% in CD3(+) intraepithelial lymphocytes). Both CD3(-) and CD3(+) cells displayed a type I cytokine profile (interferon-gamma > tumor necrosis factor-alpha > interleukin-2; undetectable interleukin-4 and interleukin-10). In addition to their activated phenotype, subsets of natural killer-like intraepithelial lymphocytes expressed CD8alphaalpha and intracellular CD3epsilon chain, showing the existence of heterogeneity within this cell lineage.

CONCLUSIONS

This is the first demonstration of functional natural killer cells within the human gut epithelium. These cells might play an important role in innate mucosal immunity (host defense and tumor surveillance) and tolerance.

Relationship between formation of aberrant crypts and acute responses of colonic epithelial cells to genotoxic treatment among inbred rat strains

DNA damage such as chemical carcinogen or gamma-rays induces aberrant crypts in the rat colorectum. We demonstrated that formation of aberrant crypts is different among inbred rat strains (WKAH, DA and F344/N). DA had less preneoplastic lesions in the colorectum than the others regardless of the way of DNA damage. We analyzed changes in in vivo number of colonic epithelial cells undergo mitosis, DNA synthesis and apoptosis following DNA damage histochemically. It is indicated that rapid onset of G1 arrest and termination of G2/M arrest and apoptosis in damaged epithelial cells is important to reduce subsequent formation of the preneoplastic lesions.

Autocrine IL-15 mediates intestinal epithelial cell death via the activation of neighboring intraepithelial NK cells

Intestinal intraepithelial lymphocytes (IELs), which reside between the basolateral faces of intestinal epithelial cells (IECs), provide a first-line defense against pathogens via their cytotoxic activity. Although IEC-derived IL-7 and IL-15 are key regulatory cytokines for the development and activation of IELs, we report here that IL-15 but not IL-7 mediates the reciprocal interaction between IELs and IECs, an important interaction for the regulation of appropriate mucosal immunohomeostasis. IL-15-treated IELs induced cell death in IECs via the cytotoxic activity in vitro. Among the different subsets of IL-15-treated IELs, CD4(-)CD8(-)TCR(-) IELs, which express NK marker (DX5 or NK1.1), showed the most potent syngenic IEC killing activity. These intraepithelial NK cells expressed Ly-49 molecules, NKG2 receptors, and perforin. These results suggest the possibility that the cell death program of IECs could be regulated by self-produced IL-15 through the activation of intraepithelial NK cells.

The iddm4 locus segregates with diabetes susceptibility in congenic WF.iddm4 rats

Viral antibody-free BBDR and WF rats never develop spontaneous diabetes. BBDR rats, however, develop autoimmune diabetes after perturbation of the immune system, e.g., by viral infection. We previously identified a disease-susceptibility locus in the BBDR rat, iddm4, which is associated with the development of autoimmune diabetes after treatment with polyinosinic:polycytidylic acid and an antibody that depletes ART2(+) regulatory cells. We have now developed lines of congenic WF.iddm4 rats and report that in an intercross of N5 generation WF.iddm4 rats, approximately 70% of animals either homozygous or heterozygous for the BBDR origin allele of iddm4 became hyperglycemic after treatment to induce diabetes. Fewer than 20% of rats expressing the WF origin allele of iddm4 became diabetic. Testing the progeny of various recombinant N5 WF.iddm4 congenic rats for susceptibility to diabetes suggests that iddm4 is centered on a small segment of chromosome 4 bounded by the proximal marker D4Rat135 and the distal marker D4Got51, an interval of <2.8 cM. The allele at iddm4 has 79% sensitivity and 80% specificity in prediction of diabetes in rats that are segregating for this locus. These characteristics suggest that iddm4 is one of the most powerful non-major histocompatibility complex determinants of susceptibility to autoimmune diabetes described to date.