Function of alpha beta TCR+ intestinal intraepithelial lymphocytes: Th1- and Th2-type cytokine production by CD4+CD8- and CD4+CD8+ T cells for helper activity

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.

Glutamine prevents total parenteral nutrition-associated changes to intraepithelial lymphocyte phenotype and function: a potential mechanism for the preservation of epithelial barrier function

Total parenteral nutrition (TPN) results in a number of derangements to the intestinal epithelium, including a loss of epithelial barrier function (EBF). As TPN supplemented with glutamine has been thought to prevent this loss, this article further defined the impact of glutamine on EBF, and investigated potential mechanisms that contributed to the preservation of EBF. C57BL/6J male mice were randomized to enteral nutrition (control), TPN, or TPN supplemented with glutamine (TPN+GLN). Changes in intraepithelial lymphocyte (IEL)-derived cytokine expression were measured, and EBF was assessed with electrophysiologic methods and assessment of junctional protein expression. TPN resulted in a significant decline in EBF, and this loss of EBF was significantly prevented in the TPN+GLN group. Coincident with these changes was a loss of intraepithelial lymphocyte (IEL, mucosal lymphocyte)-derived IL-10 and increase in interferon-gamma (IFN-gamma) expression, and a decline in IEL numbers in the TPN group. A prevention in the increase in IFN-gamma and decline in IL-10 expression was seen in the TPN+GLN group. To determine the mechanism responsible for these glutamine-associated cytokine changes, we tested whether blockade of the IL-7 signaling pathway between epithelial cells (EC) and IEL would prevent these changes; however, blockade failed to influence IEL-derived cytokine changes. Glutamine-supplemented TPN leads to a specific IEL-derived cytokine profile, which may account for the preservation of EBF; and such action may be due to a direct action of glutamine on the IEL.

Enteral versus parenteral nutrition: effect on intestinal barrier function

Total parenteral nutrition (TPN), or the complete absence of enteral nutrients, is commonly used in a clinical setting. However, a major consequence of TPN administration is the development of mucosal atrophy and a loss of epithelial barrier function (EBF); and this loss may lead to an increase in clinical infections and septicemia. Our laboratory has investigated the mechanism of this TPN-associated loss of EBF using a mouse model. We have demonstrated that the mucosal lymphoid population significantly changes with TPN, and leads to a rise in interferon gamma (IFN-gamma) and decline in interleukin-10 (IL-10) expression-both of which contribute to the loss of EBF. Associated with these cytokine changes is a dramatic decline in the expression of tight junction and adherens junction proteins. This article discusses the potential mechanisms responsible for these changes, and potential strategies to alleviate this loss in EBF.

Intestinal epithelial cell-derived interleukin-7: A mechanism for the alteration of intraepithelial lymphocytes in a mouse model of total parenteral nutrition

Total parenteral nutrition (TPN), with the absence of enteral nutrition, results in profound changes to both intestinal epithelial cells (EC) as well as the adjacent intraepithelial lymphocyte (IEL) population. Intestinal EC are a rich source of IL-7, a critical factor to support the maintenance of several lymphoid tissues, and TPN results in marked EC changes. On this basis, we hypothesized that TPN would diminish EC-derived IL-7 expression and that this would contribute to the observed changes in the IEL population. Mice received enteral food and intravenous crystalloid solution (control group) or TPN. TPN administration significantly decreased EC-derived IL-7 expression, along with significant changes in IEL phenotype; decreased IEL proliferation; and resulted in a marked decrease in IEL numbers. To better determine the relevance of TPN-related changes in IL-7, TPN mice supplemented with exogenous IL-7 or mice allowed ad libitum feeding and treated with exogenous administration of anti-IL-7 receptor (IL-7R) antibody were also studied. Exogenous IL-7 administration in TPN mice significantly attenuated TPN-associated IEL changes, whereas blocking IL-7R in normal mice resulted in several similar changes in IEL to those observed with TPN. These findings suggest that a decrease in EC-derived IL-7 expression may be a contributing mechanism to account for the observed TPN-associated IEL changes.

Colon cancer and the immune system: The role of tumor invading T cells

Colon cancer is still one of the leading causes of cancer death worldwide. Although the host immune system has been shown to react against tumor cells, mainly through tumor infiltrating lymphocytes and NK cells, tumor cells may utilize different ways to escape anti-tumor immune response. Tumor infiltration of CD8+ and CD4+ (T-bet+) effector T cells has been attributed to a beneficial outcome, and the enhancement of T cell activation through T cell receptor stimulation and co-stimulatory signals provides promising strategies for immunotherapy of colon cancer. Growing evidence supports a role for the Fas/FasL system in tumor immunology, although the mechanisms and consequences of FasL activation in colon cancer are not completely understood. In animal models, depletion of regulatory T cells (CD4+ CD25+ T cells) can enhance the anti-tumor immune response under certain conditions. Taken together, recent insights in the immune reaction against colon carcinoma have provided new approaches to immunotherapy, although much remains to be learned about the exact mechanisms.

Escherichia coli Shiga toxin 1 enhances il-4 transcripts in bovine ileal intraepithelial lymphocytes

Shiga toxin 1 (Stx1) blocks the activation of bovine peripheral and intraepithelial lymphocytes (IEL), implying that the toxin has the potential to retard the host's immune response during intestinal colonization of cattle with human pathogenic Stx-producing Escherichia coli (STEC). Since Stx1 does not eliminate affected lymphocytes by causing cellular death, we assumed that Stx1 disturbs the integrity of the immune regulatory network. We therefore assessed the impact of Stx1 on the expression of selected chemokine and cytokine genes in vitro by real-time RT-PCR and by quantitation of intracellular cytokine proteins. While Stx1 did not alter the amount of mRNA specific for interleukin (IL)-2, IL-10, gamma interferon (IFN-gamma), transforming growth factor beta (TGF-beta), IL-8, 10kDa interferon inducible protein (IP-10), and monocyte chemoattractant protein 1 (MCP-1) in cultured ileal IEL (iIEL), minute concentrations of Stx1 led to an up to 40-fold increase of il-4 transcripts within 6-8h of incubation. Comparative experiments with peripheral lymphocytes revealed that the effect was specific for iIEL. The enhancement of il-4 transcripts in iIEL was not accompanied by apoptosis but required the enzymatic activity of the holotoxin. Nevertheless, iIEL retained their ability to synthesize proteins in the presence of Stx1: 40% of iIEL could be stimulated to synthesize IFN-gamma while less than 10% expressed IL-4 or TGF-beta. Furthermore, iIEL were found to produce granulocyte chemoattractants, but the release of these substances was not different in iIEL cultures incubated with or without Stx1. Although Stx1 did not affect the numbers of iIEL producing either cytokine, these findings point to an altered responsiveness of IEL during bovine STEC infections and shed light on the initial effects Stx1 exerts on the local adaptive immune system.

MyD88-dependent signaling for IL-15 production plays an important role in maintenance of CD8 alpha alpha TCR alpha beta and TCR gamma delta intestinal intraepithelial lymphocytes

Interaction between commensal bacteria and intestinal epithelial cells (i-ECs) via TLRs is important for intestinal homeostasis. In this study, we found that the numbers of CD8alphaalpha TCRalphabeta and TCRgammadelta intestinal intraepithelial lymphocytes (i-IELs) were significantly decreased in MyD88-deficient (-/-) mice. The expression of IL-15 by i-ECs was severely reduced in MyD88(-/-) mice. Introduction of IL-15 transgene into MyD88(-/-) mice (MyD88(-/-) IL-15 transgenic mice) partly restored the numbers of CD8alphaalpha TCRalphabeta and TCRgammadelta i-IELs. The i-IEL in irradiated wild-type (WT) mice transferred with MyD88(-/-) bone marrow (BM) cells had the same proportions of i-IEL as WT mice, whereas those in irradiated MyD88(-/-) mice transferred with WT BM cells showed significantly reduced proportions of CD8alphaalpha TCRalphabeta and TCRgammadelta i-IELs, as was similar to the proportions found in MyD88(-/-) mice. However, irradiated MyD88(-/-) IL-15 transgenic mice transferred with WT BM cells had increased numbers of CD8alphaalpha TCRalphabeta and TCRgammadelta subsets in the i-IEL. These results suggest that parenchymal cells such as i-ECs contribute to the maintenance of CD8alphaalpha TCRalphabeta and gammadelta i-IELs at least partly via MyD88-dependent IL-15 production.

Oral antigen induces antigen-specific activation of intraepithelial CD4+ lymphocytes but suppresses their activation in spleen

Intraepithelial lymphocytes (IELs) are considered to drive immune surveillance of the epithelial layer to the mucosa, which is initially exposed to exogenous antigens. However, how IELs are activated by orally administered antigens remains unclear. To clarify this mechanism, we fed ovalbumin (OVA) to T cell receptor transgenic (TCR-Tg) mice with OVA-specific MHC class II-restricted TCR and found that the cytotoxic activity of IELs was increased against both NK and LAK target cells, but notably reduced after depleting CD8 + IELs. Cytoplasmic staining showed that the production of IFN-gamma and IL-2 was increased in mice fed with OVA both in the supernatant of cultured IELs with immobilized anti-CD3 mAb and in fresh CD4+ IELs. In contrast, the cytotoxic activity against NK and LAK target cells and the production of IL-2 and IFN-gamma was decreased in splenic T cells from mice fed with OVA. However, when the splenic T cells from these mice were cultured with OVA and IL-2, IFN-gamma production recovered. The decreased response demonstrated the clonal anergy of T cells. Furthermore, tumor growth was enhanced in TCR-Tg mice carrying an OVA-transfected counterpart A20 B cell lymphoma (OVA-A20) and fed with OVA. These results indicate that the oral administration of soluble antigens can activate CD4+ IELs in an antigen-specific manner but induces hyporesponsiveness in the spleen. In addition, Th1-type cytokines produced by activated CD4+ IEL might provide a bystander effect on the cytotoxic activity of IELs.

Oral administration of bovine colostrum stimulates intestinal intraepithelial lymphocytes to polarize Th1-type in mice

Th1 stimulus for Th2-skewed immune response during infancy is important for reduction of incidence of allergic diseases. We examined effects of oral administration of bovine colostrum on local immunity in intestine in adult mice. C57BL/6 mice were orally given bovine colostrum or control milk for 1, 3 or 6 months and intestinal microflora, fecal IgA, and lymphocyte population of gut-associated lymphoid tissues and their abilities of cytokine production were examined. Although the cell populations of intestinal intraepithelial lymphocytes (i-IEL) were not remarkably changed, the T cells in i-IEL were polarized to Th1 type after oral administration of bovine colostrum. Intestinal microflora and IgA levels in feces were not changed by oral administration of bovine colostrum. These results suggest that colostrum stimulates directly to i-IEL to polarize Th1 type, which may protect from infectious diseases and allergic diseases mediated by Th2 type responses.

Intra-epithelial T cells in coeliac disease

Coeliac disease is an enteropathy associated with dietary gluten which occurs in individuals with a genetic predisposition. The pathogenesis remains obscure although it is clear that only certain parts of the gliadin molecule are toxic and there is considerable evidence of immunological activity, including antibody production. In this issue of European Journal of Gastroenterology and Hepatology Carton et al. present evidence in favour of an inherent depletion of CD4CD8 T cells, which could result in a loss of oral tolerance to ingested gliadin. Using flow cytometry they also demonstrated that the classic T-cell infiltration of coeliac disease is not due to an increase in T cells but is an apparent increase associated with a relative decrease in enterocytes as a result of the change in architecture of the mucosa. These could be important fundamental observations in helping to unravel the pathogenesis of coeliac disease.

Complete replacement of tracheal epithelia by the host promotes spontaneous acceptance of orthotopic tracheal allografts in rats

BACKGROUND

Tracheal immunogenicity has been controversial. Although replacement of allotracheal epithelia by the host epithelia has been reported in rat orthotopic tracheal grafting, the immunological effect of epithelial replacement is still uncertain.

METHODS

We performed orthotopic tracheal grafting of nine cartilage rings in the following groups: 1, Lewis --> Lewis (n = 30); 2, ACI --> DA (n = 25); 3, Lewis --> F344 (n = 23); 4-A, DA --> Lewis (n = 41); 4-B, DA --> Lewis with tacrolimus therapy (1 mg/kg/d for 10 days) starting from the day of the operation (n = 31); 4-C, retransplantation of DA allografts to secondary naive Lewis rats 10 or 15 days after primary grafting (n = 11); 4-D, DA --> Lewis with tacrolimus therapy starting from postoperative day 10 (n = 6). Survival times and histopathology were assessed. Epithelial replacement was evaluated by immunohistochemistry.

RESULTS

All rats survived in groups 1, 2, and 3. Even in the fully histoincompatible group 4-A, survival ratio on day 120 was 15%. Epithelial replacement was in progress on day 10 in this group. However, all tacrolimus-treated rats died by day 54 and epithelial replacement did not occur on days 30 and 50 in group 4-B. In group 4-C, retransplantation after complete epithelial replacement increased the long-surviving rats. In group 4-D, all rats receiving tacrolimus therapy after complete epithelial replacement survived over 120 days.

CONCLUSIONS

These results suggest that complete replacement of tracheal epithelia by the host promotes spontaneous acceptance of orthotopic tracheal allografts in rats.

CD4+CD8+ human small intestinal T cells are decreased in coeliac patients, with CD8 expression downregulated on intra-epithelial T cells in the active disease

BACKGROUND/OBJECTIVE

The intestinal lesion of coeliac disease is thought to be initiated and exacerbated by dysregulation of local T-lymphocyte sub-populations. This study examines changes in intestinal T cells from coeliac patients, with a particular focus on CD4CD8 T cells, immunoregulatory cells normally found in relatively high proportions in the small intestine.

METHODS

Cells were obtained from duodenal biopsies from active and treated coeliac patients using chelating and reducing agents (epithelial layer) followed by collagenase treatment (lamina propria). Cell yield and viability were assessed and flow cytometric analysis was used to examine CD4CD8 T cells and to quantify CD8 expression.

RESULTS

Surprisingly, total T-cell yields in the epithelial layer did not increase in active coeliac disease although enterocyte counts decreased significantly, giving an appearance of infiltration. In active coeliac patients, CD4CD8 T cell percentages were significantly decreased in both the epithelial layer and lamina propria. Levels of CD8 expression by CD4CD8 T cells in the epithelial layer were decreased significantly in patients with active coeliac disease. CD4CD8 T cell proportions did not return to normal in treated coeliac patients whose villous architecture had responded to gluten withdrawal.

CONCLUSIONS

No increase of intra-epithelial lymphocytes in the coeliac lesion may require us to reconsider the definition of coeliac disease as an inflammatory condition. Low CD4CD8 populations in treated as well as untreated coeliac patients indicate that these T cells are inherently absent in individuals genetically predisposed to coeliac disease.

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An important regulatory role for CD4+CD8 alpha alpha T cells in the intestinal epithelial layer in the prevention of inflammatory bowel disease

The normal immunoregulatory mechanisms that maintain homeostasis in the intestinal mucosa, despite continuous provocation by environmental antigens, are jeopardized in inflammatory bowel diseases. Although previous studies have suggested that intestinal intraepithelial lymphocytes prevent spontaneous intestinal inflammation, there is limited knowledge about the characteristics of regulatory cells in the intestinal intraepithelial lymphocytes population. Here we show that CD4(+)CD8 alpha alpha(+) double-positive cells present in the intestinal intraepithelial lymphocytes population can suppress T helper 1-induced intestinal inflammation in an IL-10-dependent fashion. CD4(+) T cells stimulated along the Th2 but not the Th1 lineage, when transferred to RAG-1-/- mice, acquire CD8 alpha alpha expression on reaching the intestinal epithelium, and on arrival there, augment their production of IL-10. We show that a precursor CD4(+) T cell after limited, but not repeated, stimulation by IL-4 is able to become a double-positive-regulatory cell on exposure to the intestinal microenvironment in mice. Both CD8 alpha alpha acquisition and IL-10 production depend critically on the NF-kappa B-GATA-3-axis that we have previously shown is essential for differentiation to the Th2 phenotype and for the induction of airway inflammation. Our studies identify a mechanism for the generation of regulatory T cells in the intestine that may play an important role in controlling inflammatory bowel disease.

Alteration of intestinal intraepithelial lymphocytes after massive small bowel resection

BACKGROUND

Intraepithelial lymphocytes (IEL) comprise the inner most layer of the gut immune system, and play a critical role in protecting the host from enteric organisms. Massive small bowel resection (MSBR) is one such clinical condition where patients are at particularly high risk for the development of such enteric infectious complications. Because of this, we hypothesized that the IEL may change significantly after the formation of a MSBR. To address this, a mouse model of MSBR was created and the acute phenotypic and functional characteristics of the IEL were studied.

MATERIALS AND METHODS

Mice underwent a 70% mid-small bowel resection. After 7 days, IEL were isolated and analyzed for phenotypic changes by flow cytometry. IEL cytokine expression was performed with semiquantitative polymerase chain reaction techniques. To assess the functional significance of these changes, IEL proliferative response was assessed in vitro.Results. MSBR led to significant decreases in specific IEL subpopulations: CD 44+ (used as a marker of cell maturity); CD 8alphabeta+ (marker of thymic derivation), and CD 69+ (marker of T cell activation). Compared with controls, IEL TNF-alpha mRNA expression increased 84%, while IL-2 and IL-10 mRNA expression decreased by 69 and 72%, respectively. Spontaneous proliferation of IEL in the MSBR group was significantly higher than controls, however, proliferation failed to increase with T cell stimulation.Conclusion. These changes suggest a shift to a more immature and possibly less activated cell population. It is possible that such alterations may play an important role in the increase in enterically derived infections in patients with MSBR.

Interferon-gamma expression by intraepithelial lymphocytes results in a loss of epithelial barrier function in a mouse model of total parenteral nutrition

OBJECTIVE

To determine the etiology of the loss of epithelial barrier function observed with the administration of total parenteral nutrition (TPN) in a mouse model.

SUMMARY BACKGROUND DATA

Removal of enteral nutrition with the administration of TPN is associated with a loss of intestinal epithelial barrier function. The etiology of this barrier loss is not clear. Because intraepithelial lymphocytes (IELs) produce a number of cytokines that may alter epithelial permeability, the authors investigated IEL cytokine expression in a mouse model of TPN.

METHODS

Adult C57BL/6 mice received TPN or enteral diet for 7 days. IELs were subsequently harvested and the mRNA expression of cytokines was measured. Epithelial barrier function was assessed in vitro with 51Cr-EDTA in Ussing chambers and was expressed as the permeability coefficient (Papp).

RESULTS

IEL mRNA expression of interferon-gamma (IFN-gamma) rose from 0.14 +/- 0.07 in the control (enterally fed) group to 0.44 +/- 0.11 attomoles/microL in the TPN group (P <.05). Transforming growth factor-beta1 declined slightly but not significantly, from 0.75 +/- 0.35 to 0.55 +/- 0.18 attomoles/microL in the control and TPN groups, respectively. Epithelial barrier function declined significantly with TPN compared to controls. To assess the relevance of IFN-gamma changes, permeability in IFN-gamma knockout mice was studied. Barrier function was significantly higher in IFN-gamma knockout mice on TPN compared to C57BL/6 mice that received TPN.

CONCLUSIONS

IEL cytokine expression changes significantly with TPN administration. The partial correction with IFN-gamma knockout mice suggests that an upregulation of IFN-gamma expression is one mechanism responsible for the loss of the epithelial barrier associated with TPN.

CD8 alpha-deficient mice are highly susceptible to 5-fluorouracil-induced lethality

Intestinal intraepithelial lymphocytes (i-IEL) expressing CD8 alpha are located in the intestine and may confer protection against invasion of intestinal microflora. We found that mice rendered deficient in CD8 alpha molecules by homologous recombination were susceptible to 5-fluorouracil (5-FU)-induced lethality accompanied by translocation of members of the enterobacteria. The number of i-IEL was greatly reduced on day 6 after 5-FU administration in both CD8 alpha(+/-) mice and CD8 alpha(-/-) mice, whereas the recovery of the level of i-IEL thereafter was significantly impaired in CD8 alpha(-/-) mice compared with that in CD8 alpha(+/-) mice. The ability of i-IEL to produce gamma interferon in response to immobilized T-cell receptor (TCR) alpha beta or TCR gamma delta monoclonal antibodies was significantly lower in CD8 alpha(-/-) mice than in CD8 alpha(+/-) mice. Transfer of CD8(+) i-IEL conferred significant protection against 5-FU-induced lethality in CD8 alpha(-/-) mice. The results suggest that CD8(+) i-IEL play an important role in protection against 5-FU-induced lethality with translocation of Enterobacteriaceae.

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.

Identification and characterization of lymphoid precursors in the murine intestinal epithelium

Although in vivo evidence supports a role for the murine intestinal epithelium in the extrathymic generation of certain intraepithelial T lymphocytes (IEL), no intraepithelial cells with in vitro lymphoid progenitor potential have yet been demonstrated. Using reaggregate fetal thymic organ culture techniques, we show that a subset of CD3(-) cells isolated from the intestinal epithelium of young mice is capable of generating T cells (alpha beta and gamma delta) and NK1.1(+) cells in vitro. A novel IEL subset bearing a low level of CD45 was identified and found to comprise cells expressing highly immature lymphoid markers including CD34, c-kit, CD122, CD127 and high levels of CD16 and CD44. This subset represents 20-30% of intraepithelial CD45(+) cells from 4-week-old wild-type and nude mouse strains and contains cells with in vitro T cell differentiation capacity. The identification of such an early pluripotent precursor phenotype within the intestinal epithelium implies that the potential for T cell generation exists at this site, and suggests that extrathymic T cell generation may occur within the epithelium itself.

Cytokines as adjuvants for the induction of mucosal immunity

Safe nasal vaccines capable of promoting both mucosal and systemic immunity are needed for effective protection against bacterial and viral pathogens. While parenteral cytokine treatment could lead to unwanted toxicity, the nasal delivery route results in low but biologically active serum cytokine levels. Interleukin (IL)-6, IL-1 and IL-12, which promote either Th2- or Th1-type responses, respectively, also enhance systemic immunity to co-administered antigens. The chemoattractants lymphotactin (Lptn), RANTES and defensins also exerted adjuvant activity for systemic immunity when nasally administered with antigens. However, each cytokine or innate factor promoted a distinct pattern of T helper cell responses and corresponding IgG subclass response. Interleukin-12, IL-1, and the chemokines Lptn and RANTES promote mucosal immunity. In contrast, nasal IL-6 and defensins failed to induce mucosal S-IgA Ab responses, suggesting that mechanisms more complex than T cell activation and chemotaxis are required for the development of mucosal immunity after nasal delivery of cytokines.

Elimination of colonic patches with lymphotoxin beta receptor-Ig prevents Th2 cell-type colitis

Past studies have shown that colonic patches, which are the gut-associated lymphoreticular tissues (GALT) in the colon, become much more pronounced in hapten-induced murine colitis, and this was associated with Th2-type T cell responses. To address the role of GALT in colonic inflammation, experimental colitis was induced in mice either lacking organized GALT or with altered GALT structures. Trinitrobenzene sulfonic acid was used to induce colitis in mice given lymphotoxin-beta receptor-Ig fusion protein (LTbetaR-Ig) in utero, a treatment that blocked the formation of both Peyer's and colonic patches. Mice deficient in colonic patches developed focal acute ulcers with Th1-type responses, whereas lesions in normal mice were of a diffuse mucosal type with both Th1- and Th2-type cytokine production. We next determined whether LTbetaR-Ig could be used to treat colitis in normal or Th2-dominant, IFN-gamma gene knockout (IFN-gamma(-/-)) mice. Four weekly treatments with LTbetaR-Ig resulted in deletion of Peyer's and colonic patches with significant decreases in numbers of dendritic cells. This pretreatment protected IFN-gamma(-/-) mice from trinitrobenzene sulfonic acid-induced colitis; however, in normal mice this weekly treatment was less protective. In these mice hypertrophy of colonic patches was seen after induction of colitis. We conclude that Th2-type colitis is dependent upon the presence of colonic patches. The effect of LTbetaR-Ig was mediated through prevention of colonic patch hypertrophy in the absence of IFN-gamma. Thus, LTbetaR-Ig may offer a possible treatment for the Th2-dominant form of colitis.

Alteration of V beta usage and cytokine production of CD4+ TCR beta beta homodimer T cells by elimination of Bacteroides vulgatus prevents colitis in TCR alpha-chain-deficient mice

A major pathogenic factor for the development of inflammatory bowel disease (IBD) is the breakdown of the intestinal homeostasis between the host immune system and the luminal microenvironment. To assess the potential influence of luminal Ags on the development of IBD, we fed TCR alpha(-/-) mice an elemental diet (ED). ED-fed TCR alpha(-/-) mice showed no pathologic features of IBD, and their aberrant mucosal B cell responses were suppressed. Similar numbers of CD4(+), TCR betabeta homodimer T cells (betabeta T cells) were developed in the colonic mucosa of ED-fed mice; however, Th2-type cytokine productions were lower than those seen in diseased regular diet (RD)-fed mice. The higher cytokine production in diseased RD-fed mice could be attributed to the high incidence of Bacteroides vulgatus (recovered in 80% of these mice), which can induce Th2-type responses of colonic CD4(+), betabeta T cells. In contrast, ED-fed TCR alpha(-/-) mice exhibited a diversification of Vbeta usage of betabetaT cell populations from the dominant Vbeta8 one associated with B. vulgatus in cecal flora to Vbeta6, Vbeta11, and Vbeta14. Rectal administration of disease-free ED-fed mice with B. vulgatus resulted in the development of Th2-type CD4(+), betabeta T cell-induced colitis. These findings suggest that the ED-induced alteration of intestinal microenvironments such as the enteric flora prevented the development of IBD in TCR alpha(-/-) mice via the immunologic quiescence of CD4(+), betabeta T cells.

Mice deficient in Th1- and Th2-type cytokines develop distinct forms of hapten-induced colitis

BACKGROUND & AIMS

Most experimental models for inflammatory bowel disease in mice are associated with production of interferon (IFN)-gamma and other proinflammatory cytokines. We hypothesized that T-helper 2 (Th2)-type cells could also contribute to the colitis and cause inflammation different than that mediated by Th1-type cells.

METHODS

Trinitrobenzene sulfonic acid (TNBS)-induced colitis in C57BL/6 background mice genetically deficient in interleukin (IL)-12 p40 (IL-12(-/-)), IFN-gamma (IFN-gamma(-/-)), or IL-4 (IL-4(-/-)) was examined in comparison with control mice (C57BL/6(+/+)).

RESULTS

C57BL/6(+/+), IFN-gamma(-/-), and IL-12(-/-) mice developed patterns of colitis characterized by distortion of crypts, loss of goblet cells, and mononuclear cell infiltration with fibrosis of the mucosal layer. IL-4(-/-) mice had greater mortality than other groups because of penetrating ulcers; however, survivors developed milder lesions that were limited to focal acute ulceration. Colonic CD4(+) T cells from normal, IFN-gamma(-/-), or IL-12(-/- )mice produced both IL-4 and IL-5.

CONCLUSIONS

In TNBS colitis, Th1-like cytokine responses induce fatal, acute, transmural, and focal types of lesions, whereas Th2-like cytokine responses play a significant role in the diffuse atrophic changes in crypts and the mucosal layer that occur in the late stages of this disease.

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

The regional variation in the intraepithelial lymphocytes (IELs) in the small intestine was examined in BALB/c male and female mice and C3H/He and C57BL/6 male mice. The small intestines were taken from 11 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 flow cytometer. The number of IELs was highest in the proximal part and lowest in the distal part. The distribution of IEL subsets was markedly different between the proximal and the distal parts, and that in the middle part showed the intermediate pattern. The percentage of alphabeta T cells were higher in the distal part. In alphabeta T cell subset, the percentage of CD8alphaalpha T cells was higher in the proximal part, whereas those of CD4 and CD4CD8alphaalpha double positive T cells were higher in the distal part. In gammadelta T cell subset, no regional variations were found. The regional variations in the number and subsets of IELs showed almost the same patterns between male and female BALB/c mice and similar patterns among three strains of mice. This strongly suggests that the regional variations in the small intestinal IELs are common to mouse species.

Differential intra-epithelial lymphocyte phenotypes following Cryptosporidium parvum challenge in susceptible and resistant athymic strains of mice

The lack of immunocompetent laboratory animal models has limited our understanding of functional immune responses to Cryptosporidium parvum infection, but such responses have been studied in susceptible laboratory rodents with genetic, acquired, or induced immunodeficiencies. We previously observed that athymic C57BL/6J nude mice inoculated with C. parvum oocysts had lower or absent fecal oocyst excretion when compared to inoculated athymic BALB/cJ nude mice. This discrepancy prompted us to explore potential differences in intestinal immune responses in both strains. Prior to and after C. parvum challenge, BALB/cJ nude and C57BL/6J nude mice did not differ in either spleen cell numbers or in parasite-specific proliferation. However, both strains of mice exhibited a significant increase in intra-epithelial lymphocyte (IEL) numbers prior to and following C. parvum inoculation when compared to uninoculated controls (P<0.05). Prior to challenge, C57BL/6J nude mice had a higher percentage of both CD8+ and CD8+ gammadelta+ IEL than BALB/cJ nude mice. Following challenge, resistant C57BL/6J nude mice had a higher percentage of gammadelta+, CD4+, and CD8+ gammadelta+ IEL than uninoculated C57BL/6J nude mice and than susceptible BALB/cJ nude mice (P<0.05). Conversely, inoculated C57BL/6J nude mice had a significantly lower percentage of alphabeta+ IEL than inoculated BALB/cJ nude mice (P<0.05). We conclude that gammadelta+, CD4+, and/or CD8+ gammadelta+ IEL may influence responses to cryptosporidiosis in athymic murine models, and that the increased percentage of alphabeta+ IEL in susceptible BALB/cJ nude mice could reflect a preferential expression during chronic C. parvum infection and/or might downregulate local protective responses.

Interleukin 12 and innate molecules for enhanced mucosal immunity

Recent strategies for understanding the mechanisms underlying mucosal immune responses and subsequent development of mucosal vaccines for induction of targeted immunity now include cytokines and molecules of innate immunity. These studies have shown that cytokines influencing the development of T helper (Th) cells differentially affect the outcome of mucosal vs. systemic immune responses to mucosal vaccines. Serum antigen-specific antibody (Ab) responses were enhanced when either IL-6 or IL-12 was mucosally administered with a protein antigen, while only IL-12 induced antigen-specific mucosal IgA Ab responses. Mucosal IL-6 and IL-12 also affected the type of Th cell responses induced by CD4+ T cells from mice that received IL-12 secreted larger amounts of IFN-gamma and IL-6 when compared with mice nasally treated with IL-6. Discrepancies in the ability to enhance mucosal or systemic immune responses were also observed when human neutrophil peptide (HNP) defensins or lymphotactin were nasally coadministered with protein antigens. Only lymphotactin promoted mucosal secretory IgA (S-IgA) Ab responses while both lymphotactin and defensins enhanced systemic immunity to mucosally co-administered protein antigens. Mixed antigen-specific Th1 -and Th2-type CD4+ T cell responses were induced in the systemic compartment by both lymphotactin and the mixture of HNP-1, HNP-2, and HNP-3 defensins. However, HNPs failed to significantly enhance cytokine secretion by mucosally derived, antigen-specific CD4+ T cells relative to those isolated from the systemic compartment. In summary, these studies clearly show that IL-12 and lymphotactin are able to trigger S-IgA Ab responses and provide new avenues for the design of safe and targeted mucosal vaccines.

Intraepithelial lymphocytes coinduce nitric oxide synthase in intestinal epithelial cells

The study of mucosal immunity has revealed that complex reciprocal interactions occur between intestinal intraepithelial lymphocytes (IEL) and intestinal epithelial cells (IEC). The present study focuses on the induction of inducible nitric oxide (NO) synthase in cocultures of freshly isolated rat IEL and the rat epithelial cell line IEC-18 after the addition of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha, or lipopolysaccharide. When IEL and IEC were separated using Transwell chambers, NO synthesis was not induced, indicating that cell-cell contact was required. Culture of IEC-18 with IEL, even in the absence of inflammatory stimuli such as IL-1beta, resulted in upregulation of class I and II antigens on IEC-18, due to the interferon-gamma (IFN-gamma) that is constitutively produced by IEL. Addition of anti-IFN-gamma antibody to the NO-producing cocultures resulted in inhibition of NO synthesis as well as the upregulation of class I and II antigen expression. These data indicate that IFN-gamma production by IEL conditions IEC for the expression of other components of the inflammatory process.

gammadelta T cells regulate mucosally induced tolerance in a dose-dependent fashion

We used gammadelta TCR-deficient (TCRdelta(-/-)) mice to examine the role of gammadelta T cells for induction of mucosal responses and systemic tolerance to high versus low doses of oral antigen. When either TCRdelta(-/-) or TCRdelta(+/+) mice were immunized orally with a high dose of ovalbumin (OVA) prior to parenteral challenge, systemic IgG and IgE antibody responses were markedly reduced in both types of mice, while mucosal IgA responses were reduced only in the TCRdelta(-/-) mice. Reduced T cell proliferative responses and delayed-type hypersensitivity were seen in TCRdelta(-/-) and TCRdelta(+/+) mice given the high dose of OVA. Antigen-induced T(h)1 and T(h)2 cytokine production by splenic CD4(+) T cells was severely inhibited in orally tolerized TCRdelta(-/-) and TCRdelta(+/+) mice. In contrast, while oral tolerance associated with increased levels of IL-10 synthesis was induced by a low dose of OVA in TCRdelta(+/+) mice, the TCRdelta(-/-) mice were not tolerized and failed to produce IL-10. Our findings indicate that gammadelta T cells play a significant immunoregulatory role in IL-10-mediated, low-dose oral tolerance induction, but are not essential participants in the induction of systemic tolerance to orally introduced antigens given in larger doses.

Alteration of interleukin 4 production results in the inhibition of T helper type 2 cell-dominated inflammatory bowel disease in T cell receptor alpha chain-deficient mice

T cell receptor alpha chain-deficient (TCR-alpha(-/-)) mice are known to spontaneously develop inflammatory bowel disease (IBD). The colitis that develops in these mice is associated with increased numbers of T helper cell (Th)2-type CD4(+)TCR-betabeta (CD4(+)betabeta) T cells producing predominantly interleukin (IL)-4. To investigate the role of these Th2-type CD4(+)betabeta T cells, we treated TCR-alpha(-/-) mice with anti-IL-4 monoclonal antibody (mAb). Approximately 60% of TCR-alpha(-/-) mice, including those treated with mock Ab and those left untreated, spontaneously developed IBD. However, anti-IL-4 mAb-treated mice exhibited no clinical or histological signs of IBD, and their levels of mucosal and systemic Ab responses were lower than those of mock Ab-treated mice. Although TCR-alpha(-/-) mice treated with either specific or mock Ab developed CD4(+)betabeta T cells, only those treated with anti-IL-4 mAb showed a decrease in Th2-type cytokine production at the level of mRNA and protein and an increase in interferon gamma-specific expression. These findings suggest that IL-4-producing Th2-type CD4(+)betabeta T cells play a major immunopathological role in the induction of IBD in TCR-alpha(-/-) mice, a role that anti-IL-4 mAb inhibits by causing Th2-type CD4(+)betabeta T cells to shift to the Th1 type.

Optimisation of a technique for isolating lymphocyte subsets from human endometrium

Human endometrium is a rich source of lymphocytes which may have unique immunoregulatory functions. The aim of this study was to compare current procedures for endometrial tissue disaggregation, and optimise a method for isolation of endometrial lymphocytes. Tissue was obtained from 41 women undergoing elective hysterectomy or dilation and curettage (D&C) for reasons of benign non-endometrial pathology. Specimens were exposed to reduction/chelation, mechanical or enzymatic disruption. Optimal single cell suspensions of high yields (mean 8.8 x 10(6) range 3.5-18 x 10(6)lymphs) and good viability (60%) were obtained, using a combination of collagenase IV (200 U/ml) and DNase I (35 U/ml). Suspensions were further purified by density gradient centrifugation. Multi-colour flow cytometry was used for analysis of endometrial lymphocyte subsets. Cell suspensions were stained with mAbs specific for CD3, CD4, CD8, CD56, CD45 and CD14, and it was clearly shown that the developed method had no effect on surface glycoprotein expression. Phenotypic analysis revealed consistent populations of endometrial large granular lymphocytes (CD56+CD3-) 54.16%, and T-cells (CD3+) 37.73%. This technique was applicable to the characterisation of T-cell populations, including CD8+ (56.6%), CD4+ (44.0%), and particularly smaller populations of CD4+CD8+(3.56%), CD4-CD8-(3.34%) and CD56+(6.3%) due to it's sensitivity. In conclusion, optimised enzymatic digestion, in combination with flow cytometry provides an effective method for phenotypic examination of small endometrial lymphocyte subpopulations.

Modulation of cytokine responses of murine CD8+ alphabeta intestinal intraepithelial lymphocytes by IL-4 and IL-12

The immune responses of the intestine mucosa feature the noninflammatory type, such as IgA production and oral tolerance. Th2 type cytokines have been implicated in the induction of these noninflammatory responses. In the present study, cytokine responses of CD8+ and CD4+ TCRalphabeta+ intestinal intraepithelial lymphocyte (alphabeta iIEL) subsets to TCR stimulation under the influence of IL-12, IL-4, or CD28 costimulation were examined. IL-12 enhanced production of IL-10 and IFN-gamma by the CD8alphabeta+ alphabeta iIEL significantly but only marginally affected the CD8alphaalpha+ subset, whereas IL-4 induced IL-4, IL-5, and IL-10 production and augmented TGF-beta production by both subsets. CD28 costimulation induced production of Th2 cytokines by CD4+ iIEL in the absence of exogenous IL-4. Unlike lymph node CD4+ cells, the CD28 costimulation-induced Th2 differentiation of CD4+ iIEL was not inhibited by IFN-gamma. These results demonstrate active cytokine production by CD4+, CD8alphabeta+, as well as CD8alphaalpha+ alphabeta iIEL. The Th2- skewed cytokine profile of CD8alphaalpha+ alphabeta iIEL and the IFN-gamma-resistance of Th2 differentiation of the CD4+ alphabeta iIEL suggest that both iIEL subsets contribute to the induction of noninflammatory mucosal immune responses.

Hapten-induced colitis is associated with colonic patch hypertrophy and T helper cell 2-type responses

To investigate the potential involvement of T helper (Th)2-type responses in murine models of intestinal inflammation, we used trinitrobenzene sulfonic acid (TNBS)-hapten to induce inflammatory bowel disease in situations where Th1-type responses with interferon (IFN)-gamma synthesis are either diminished or do not occur. Intracolonic administration of TNBS to either normal (IFN-gamma+/+) or Th1-deficient IFN-gamma knockout (IFN-gamma-/-) BALB/c mice resulted in significant colitis. In IFN-gamma-/- mice, crypt inflammation was more severe than in IFN-gamma+/+ mice and was accompanied by hypertrophy of colonic patches with a lymphoepithelium containing M cells and distinct B and T cell zones resembling Peyer's patches. Hapten-specific, colonic patch T cells from both mouse groups exhibited a Th2 phenotype with interleukin (IL)-4 and IL-5 production. TNBS colitis in normal mice treated with anti-IL-4 antibodies or in IL-4(-/-) mice was less severe than in either IFN-gamma+/+ or IFN-gamma-/- mice. Our findings now show that the Th2-type responses in TNBS colitis are associated with colonic patch enlargement and inflammation of the mucosal layer and may represent a model for ulcerative colitis.

Differential Effects of IL-2 and IL-15 on the Death and Survival of Activated TCRγδ+ Intestinal Intraepithelial Lymphocytes

TCRγδ+ cells are enriched in the intestine mucosa and constitute approximately half of the intestinal intraepithelial lymphocytes (iIEL) in mice. They are likely activated by self and foreign Ags in situ, but little is known about how the activated γδ iIEL are regulated. In the iIEL compartment, IL-2 is produced by activated TCRαβ+ iIEL, and IL-15 message is detected in iIEL and in the epithelial cells. We found surface expression of IL-2 as well as IL-15Rs on activated γδ iIEL, and examined the effects of IL-2 and IL-15 on the survival and death of γδ iIEL during secondary stimulation through TCR. We found that both cytokines supported growth of the restimulated γδ iIEL, but exerted different effects on their survival. A significant higher number of live cells were recovered from the γδ iIEL cultures restimulated in IL-15 than in IL-2. Quantitation of apoptotic cells showed more cell death in the IL-2 group than in the IL-15 group. The cell death was associated with restimulation through TCR and was not caused by insufficient growth factor, thus representing activation-induced cell death. Western blot analyses found no difference in the levels of Bcl-2 and Bax proteins between the two groups. However, the level of Bcl-xL protein diminished with time in the IL-2 group whereas the level was sustained in the IL-15 group, which may contribute to the pro-survival effect of IL-15. These results demonstrated that the survival of activated γδ iIEL is differentially regulated by IL-2 and IL-15.

Mucosally Induced Systemic T Cell Unresponsiveness to Ovalbumin Requires CD40 Ligand-CD40 Interactions

CD40 ligand (CD40L) gene-disrupted (CD40L−/−) mice were employed to examine the role of costimulatory signals via CD40L-CD40 interactions in mucosally induced tolerance. CD40L−/− and control (CD40L+/+) mice of the same C57BL/6 × 129/J background were immunized orally with 25 mg of OVA before systemic challenge with OVA in CFA. While CD40L+/+ mice showed reductions in Ag-specific T cell responses including delayed-type hypersensitivity (DTH) and proliferative responses, CD40L−/− mice underwent normal T cell responses. Further, cytokine analysis of splenic CD4+ T cells showed that both Th1-type (e.g., IFN-γ and IL-2) and Th2-type (e.g., IL-4, IL-5, IL-6, and IL-10) responses were maintained in CD40L−/− mice orally immunized with OVA, whereas these cytokine responses in CD40L+/+ mice were significantly reduced. In addition, splenic CD4+ T cells from CD40L−/− mice orally immunized with OVA provided B cell help in Ag-specific Ab-forming cells when the cells were cultured with naive B cells in the presence of Ag and CD40L-transfected cell lines. In contrast, an identical culture condition containing splenic CD4+ T cells from orally tolerized CD40L+/+ mice did not exhibit helper activity. Taken together, these findings indicate that CD40L and CD40 interactions are essential for the induction of systemic T cell unresponsiveness to orally administered Ag.

Characterization of CD4+ CD8alphaalpha+ and CD4-CD8alphaalpha+ intestinal intraepithelial lymphocytes in rats

Intestinal intraepithelial lymphocytes (i-IEL) of aged rats comprise CD4+CD8alphaalpha+ and CD4-CD8alphaalpha+ T cells expressing TCR alphabeta. In the present study, we compared characteristics between CD4+CD8alphaalpha+ and CD4-CD8alphaalpha+ i-IEL, which were purified by a cell sorter from the i-IEL of 6-month-old Lewis rats. Most of the CD4+CD8alphaalpha+ i-IEL were of the CD44(hlgh) phenotype, while CD4-CD8alphabeta+ i-IEL were CD44(low). Vbeta usage in the CD4-CD8alphaalpha+ i-IEL was much diversified, while CD4+CD8alphaalpha+ i-IEL showed a skewed Vbeta repertoire. The CD4+CD8alphaalpha+ i-IEL but not the CD4-CD8alphaalpha+ i-IEL proliferated in response to syngeneic spleen cells, which was partially inhibited by addition of anti-MHC class I mAb. The CD4+CD8alphaalpha+ i-IEL produced IFN-gamma and IL-2 but no IL-4 or transforming growth factor (TGF)-beta in response to syngeneic spleen cells, while CD4-CD8alphaalpha+ i-IEL produced abundant levels of TGF-beta but no IL-2, IFN-gamma or IL-4. CD4+CD8alphaalpha+ i-IEL proliferated in response to exogenous IL-2 but not to IL-15, while CD4-CD8alphaalpha+ i-IEL could respond to IL-15 as well as IL-2. These results suggest that a significant fraction of CD4+CD8alphaalpha+ i-IEL belongs to Th1-type T cells capable of responding to self-MHC class I, while CD4-CD8alphaalpha+ i-IEL are a unique population with a diversified Vbeta repertoire that respond to IL-15 in rats.

The interaction of intestinal epithelial cells and intraepithelial lymphocytes in host defense

Intestinal intraepithelial lymphocytes (i-IEL) are located at the basolateral surfaces of intestinal epithelial cells (i-EC) and play important roles in the homeostasis of intestinal microenvironment. i-IEL comprise unique T cell populations including CD4-CD8alphaalpha+ T cells expressing T cell receptor (TCR)alphabeta or TCRgammadelta and CD4+ CD8alphaalpha+ T cells expressing TCR alphabeta. We show here that CD4+ CD8alphaalpha+ i-IEL belongs to Th1 type T cells capable of responding to self-MHC class I on i-EC and that a significant fraction of i-IEL expressed Fas ligand (Fas-L) and induced apoptosis in the i-EC via Fas-dependent pathway. i-IEL may recognize and eliminate the effete i-EC for homeostatic regulation of intestinal epithelia. The interaction of i-EC and i-IEL through E-cadherin/alphaEbeta7 integrin is important for homing and maintenance of i-IEL in intestine. Listeria monocytogenes are also known to interact with E-cadherin on i-EC and invade into the epithelial cells. Invasion of L. monocytogenes into i-EC activated NFkappa-B and subsequently up-regulated the expression of IL-15 gene, which has a NFkappa-B binding site at the promoter region. i-IEL, especially gammadelta T cells, were significantly activated to produce Th1 type cytokines at the early stage after oral infection with L. monocytogenes in mice and rats. The activation of i-IEL coincided with a peak response of IL-15 production by i-EC after infection. Taken together, mutual interaction of i-IEL and i-EC may be important not only for homeostatic regulation but also host defense against microbial infection in intestine.

Chicken CD4, CD8alphabeta, and CD8alphaalpha T cell co-receptor molecules

New knowledge has recently been obtained about the evolutionary conservation of CD4, CD8alphaalpha, and CD8alphabeta T cell receptor (TCR) co-receptor molecules between chicken and mammals. This conservation extends from biochemical structure and tissue distribution to function. Panels of monoclonal antibodies and polyclonal antisera against different epitopes of chicken CD8 and CD4 molecules have proven their value in several recent studies. Chicken CD8 allotypes and homozygous strains carrying these allotypes have been established and these strains provide excellent models for further studies. The extensive polymorphism of CD8alpha in chickens has not been observed in any other species, suggesting that CD8alpha and CD8beta have evolved under different selective pressure in the chicken. A large peripheral blood CD4+CD8+ T cell population in chicken resembles that observed in some human individuals but the inheritance of peripheral blood CD4CD8alphaalpha T cells in the chicken is a unique observation, which suggests the presence of a single gene responsible for CD8alpha, but not CD8beta, specific expression. Despite these unique findings in chicken, the data on CD4, CD8alphaalpha, and CD8alphabeta molecules show that they have evolved before the divergence of mammalian and avian branches from their reptilian ancestors.

Gastrointestinal T lymphocytes retain high potential for cytokine responses but have severe CD4(+) T-cell depletion at all stages of simian immunodeficiency virus infection compared to peripheral lymphocytes

Gastrointestinal complications in human immunodeficiency virus (HIV) infection are indicative of impaired intestinal mucosal immune system. We used simian immunodeficiency virus (SIV)-infected rhesus macaques as an animal model for HIV to determine pathogenic effects of SIV on intestinal T lymphocytes. Intestinal CD4(+) T-cell depletion and the potential for cytokine responses were examined during SIV infection and compared with results for lymphocytes from lymph nodes and blood. Flow cytometric analysis demonstrated severe depletion of CD4(+)CD8(-) single-positive T cells and CD4(+)CD8(+) double-positive T cells in intestinal lamina propria lymphocytes (LPL) and intraepithelial lymphocytes (IEL) during primary SIV infection which persisted through the entire course of SIV infection. In contrast, CD4(+) T-cell depletion was gradual in peripheral lymph nodes and blood. Flow cytometric analysis of intracellular gamma interferon (IFN-gamma) and interleukin-4 (IL-4) production following short-term mitogenic activation revealed that LPL retained same or higher capacity for IFN-gamma production in all stages of SIV infection compared to uninfected controls, whereas peripheral blood mononuclear cells displayed a gradual decline. The CD8(+) T cells were the major producers of IFN-gamma. There was no detectable change in the frequency of IL-4-producing cells in both LPL and peripheral blood mononuclear cells. Thus, severe depletion of CD4(+) LPL and IEL in primary SIV infection accompanied by altered cytokine responses may reflect altered T-cell homeostasis in intestinal mucosa. This could be a mechanism of SIV-associated enteropathy and viral pathogenesis. Dynamic changes in intestinal T lymphocytes were not adequately represented in peripheral lymph nodes or blood.

A Mucosal Intranet: Intestinal Epithelial Cells Down-Regulate Intraepithelial, But Not Peripheral, T Lymphocytes

Epithelial cells and lymphocytes, including γδ and αβ T cells, in the gastrointestinal tract epithelium represent a major host defense intranet that is incompletely understood. Cell-to-cell interactions between intraepithelial lymphocytes (IELs) and intestinal epithelial cells (IECs) comprise this intranet, and we have assessed the role of IECs in the regulation of γδ and αβ T cell responses. When highly purified CD3+ IEL T cells were stimulated via the TCR-CD3 complex, high proliferative responses and cytokine synthesis were induced. However, the addition of viable IECs or purified IEC membranes (mIEC) down-regulated T cell proliferative and cytokine responses. Further, the inhibitory effect of mIEC was not restored by antibodies to TGF-β, CD1d, E-cadherin, or MHC class I or II. This inhibitory effect was noted for both γδ and αβ T cell subsets from IELs, and mRNA levels were reduced for both Th1 (IL-2 and IFN-γ) and Th2 (IL-4 and IL-5) cytokines in γδ and αβ IELs. In contrast, a purified membrane fraction obtained from thymocytes did not inhibit IEL proliferative responses. Further, mIEC did not inhibit splenic αβ T cell proliferative responses. These findings show that cell-to-cell interactions between intraepithelial γδ and αβ T cells and IECs occur via cell surface molecules, suggesting an intranet to prevent potential inflammatory responses at the intestinal mucosal surface.

A novel peripheral CD4+ CD8+ T cell population: inheritance of CD8alpha expression on CD4+ T cells

In this study we show the inheritance of a CD4+ CD8+ peripheral Tcell population in the H.B15 chicken strain. A large proportion of alphabeta T cells in peripheral blood (20-40%), spleen (10-20%) and intestinal epithelium (5-10%) coexpress CD4 and CD8alpha, but not CD8beta. CD4+ CD8alpha alpha cells are functionally normal T cells, since they proliferate in response to mitogens and signals delivered via the alphabeta T cell receptor as well as via the CD28 co-receptor. These cells induce in vivo a graft versus host-reaction, providing further evidence for their function as CD4+ T cells. The CD4+ CD8alpha alpha T cell population was found in 75% of the first progeny and in 100% of further progenies, demonstrating that coexpression of CD4 and CD8 on peripheral T cells is an inherited phenomenon. In addition, cross-breeding data suggest a dominant Mendelian form of inheritance. The hereditary expression of CD8alpha on peripheral CD4+ T cells in chicken provides a unique model in which to study the regulation of CD4 and CD8 expression.

Immune deviation of 2C transgenic intraepithelial lymphocytes in antigen-bearing hosts

The present study examined self-tolerance for T cell receptor (TCR) alpha beta intestinal intraepithelial lymphocytes (iIELs) using the 2C transgenic (Tg) mouse model specific for a peptide antigen (Ag) presented by the class I major histocompatibility complex H-2Ld. Although Tg+ T cells were largely deleted from the periphery of Ag+ mice, equivalent numbers of Tg iIELs were present in Ag+ compared to Ag- mice. Tg iIELs in Ag- mice contained CD8 alpha beta, CD8 alpha alpha, and CD4-CD8- subsets, whereas only CD8 alpha alpha and CD4-CD8- Tg iIEL subsets were detected in Ag+ mice. Analysis of surface markers revealed that Tg iIELs in Ag+ mice expressed decreased levels of Thy-1 and increased CD45R/B220 as compared to Ag- Tg iIELs. In response to activation with exogenous peptide or immobilized anti-TCR mAB, iIELs from Ag- mice proliferated at high levels and produced interleukin (IL)-2 and interferon (IFN)-gamma, while Tg+ iIELs from Ag+ mice proliferated at low levels and failed to produce detectable IL-2 or IFN-gamma. Activation of sorted iIEL subsets from Ag- mice revealed that CD8 alpha alpha and CD4-CD8- subsets produced low levels of IL-2 and IFN-gamma in response to activation with antigen-presenting cells and added peptide or immobilized anti-TCR mAb, while CD8 alpha beta + iIELs responded to endogenous levels of peptide. In response to APC and exogenous peptide, sorted iIEL subsets from Ag+ mice produced IL-2 and IFN-gamma, and proliferated at greatly reduced levels compared to corresponding subsets from Ag- mice. Analysis of cytokine mRNA levels revealed that activation in vitro induced IL-2 mRNA only in Ag-, but not Ag+ iIELs, whereas a high level of IL-4 mRNA induction was detected in Tg+ iIELs from Ag+ mice, and to a lesser degree, from Ag- mice. These data suggest that tolerance for Tg+ iIELs resulted in the deletion of CD8 alpha beta + subsets and the persistence of Tg+ iIEL subsets with decreased sensitivity to endogenous levels of self-peptide. A comparison of the cytokine profiles expressed by Tg+ iIEL subsets in Ag- and Ag+ mice suggested that tolerance induction had involved the functional deviation of cells from TC1 (T helper-1-like) to a less inflammatory TC2 (T helper-2-like) phenotype capable of mediating humoral immune responses in the mucosa.

Isolation and characterization of highly purified rat intestinal intraepithelial lymphocytes

The study of intestinal intraepithelial lymphocytes (IEL) has been hindered by the difficulty of isolating a population of lymphocytes which is free of epithelial cell or lamina propria cell contaminants and representative of the in vivo population of IEL in both phenotype and function. We describe an improved technique for the extraction and purification of IEL from the proximal small intestine of the rat. This technique rapidly and reproducibly isolates 5-10 x 10(6) IEL/rat with 90-95% purity and viability without the use of enzymes which affect lymphocyte function. The resulting cell population, which is 75% alpha beta T cell receptor (TCR)+, 70% CD8+, and 33% CD4+ T cells, and only 5% B cells and 2% macrophages, is of suitable purity to allow for flow cytometric analysis of the entire population of cells without requiring gating on lymphocytes. IEL are comprised of a unique T cell repertoire in that 27% of cells co-express the CD4 and CD8 molecules, but only 11% of CD4+ cells co-express CD45RC. All CD4+ cells express the alpha beta TCR, but 9% of IEL are CD8+ CD4- alpha beta TCR-. The adhesion molecules alpha 4 integrin and L-selectin are expressed on 57% and less than 1% of IEL, respectively. The isolated IEL population contains mRNA for IL-1 alpha, IL-1 beta, IL-1R, IL-1RA, IL-2, IL-6R, IFN-gamma, TGF-alpha, TGF-beta 1, and TNF-alpha. Mesenteric lymph node cells (MLNC) were examined in parallel. This technique allows for the isolation of rat IEL appropriate for phenotypic analysis by flow cytometry and for cytokine analysis by reverse transcription/polymerase chain reaction.

Cytokine gene transcription of human colonic intraepithelial lymphocytes costimulated with epithelial cells bearing HLA-DR and its inhibition by 5-aminosalicylic acid

The objectives of this study were to activate human colonic intraepithelial lymphocytes at the transcriptional level with HLA-DR+ human colonic epithelial cell line (HT29) in synergy with CD3 monoclonal antibody and to investigate the molecular mechanism for the therapeutic effects of 5-aminosalicylic acid. Lymphocytes were isolated by a mechanical method from resected colon of 22 cases and then cocultured on 10 ng/ml CD3mAb immobilized plates with HT29 which had been induced to express MHC class II molecules by interferon gamma. Flow cytometry analysis suggested that the lymphocyte population had a CD4/CD8 ratio similar to that observed in intact tissue sections and that there was no HT29 contamination of the lymphocytes isolated again from cocultured cells. The activation of intraepithelial lymphocytes showed the gene transcription of interferon gamma and tumor necrosis factor alpha, as measured by means of the reverse-transcriptase polymerase chain reaction, and this activation was antagonized by 5-aminosalicylic acid. Thus, epithelial cells bearing HLA-DR are capable of enhancing CD3-induced activation of human colonic intraepithelial lymphocytes and subject to inhibition by 5-aminosalicylic acid, the active moiety of salicylates used in inflammatory bowel disease.

T helper cell 1-type CD4+ T cells, but not B cells, mediate colitis in interleukin 10-deficient mice

Mice rendered deficient in the production of interleukin 10 (IL-10-/-) develop a chronic inflammatory bowel disease (IBD) that predominates in the colon and shares histopathological features with human IBD. Our aim was to identify which cell type(s) can mediate colitis in IL-10-/- mice. We detected an influx of immunoglobulin-positive cells into the colon and the presence of colon-reactive antibodies in the serum of IL-10-/- mice. To assess a pathogenic role for B cells, we generated a B cell-deficient (B-/-) strain of IL-10-/- mice. B-/-IL-10-/- mice acquired a severe colitis analogous to that IL-10-/- mice, implying that B cells were not the primary mediator of IBD in this model. A series of cell transfer experiments was performed to assess a pathogenic role for T cells. When IL-10-/- T cell-enriched lamina propria lymphocytes (LPL) or intraepithelial lymphocytes (IEL) were transferred into immunodeficient recombinase-activating gene (RAG)-2-/- recipients, a mild to severe colitis developed, depending on the cell number transferred. Lymphocytes recovered from the colon of transplanted RAG-2-/- mice with colitis were predominantly alpha beta TCR+CD4+, including a large proportion of CD4+CD8 alpha + cells. These cells were also CD45RB-/low and CD44+, indicative of an activated/memory population. Individual populations of CD4+CD8 alpha-, CD4+CD8 alpha + and CD4-CD8 alpha + T cells were then isolated from the lamina propria compartment of IL-10-/- mice and transferred into RAG-2-/- recipients. Only IL-10-/- CD4-expressing LPL, including both the CD4+CD8 alpha- and CD4+CD8 alpha + populations, induced colitis in recipient mice. Interferon-gamma, but little to no IL-4, was produced by CD4+CD8 alpha- and CD4+CD8 alpha + LPL recovered from the inflamed colons of RAG-2-/- recipients implicating alpha T helper cell 1 (TH1)-mediated response. We thus conclude that colitis in IL-10-/- mice is predominantly mediated by TH1-type alpha beta TCR+ T cells expressing CD4 alone, or in combination with the CD8 alpha molecule.

Interleukin 2 (IL-2) and interleukin 7 (IL-7) reciprocally induce IL-7 and IL-2 receptors on gamma delta T-cell receptor-positive intraepithelial lymphocytes

In this study, we describe the interaction between cytokine and cytokine receptor (R) for the activation and proliferation of gamma delta T-cell receptor-positive T cells (gamma delta T cells). gamma delta T cells isolated from murine intestinal intraepithelial lymphocytes (IELs) were separated into gamma delta (Dim) and gamma delta (Bright) fractions according to the intensity of gamma delta T-cell receptor expression. The gamma delta T cells express low levels of IL-2R and IL-7R as shown by flow cytometry and reverse transcriptase-PCR analysis, whereas gamma delta (Bright) T cells did not express either receptor. Our study also revealed that recombinant marine (rm)IL-2 and rmIL-7 reciprocally induced high expressions of IL-7R and IL-2R, respectively, on gamma delta (Dim) T cells but not on gamma delta (Bright) cells. Thus, treatment of gamma delta (Dim) T cells with rmIL-2 and rmIL-7 resulted in high proliferative responses, whereas gamma delta (Bright) T cells did not respond to these two cytokines. The sources of these two cytokines for gamma delta T cells were neighboring epithelial cells (IL-7) and alpha beta T cells (IL-2 and IL-7). Cytokine signaling by IL-2 and IL-7 from alpha beta T cells and epithelial cells was necessary for the expression of IL-7R and IL-2R, respectively, on a subset of gamma delta T cells (e.g., gamma delta (Dim) T cells) in mucosa-associated tissue for subsequent activation and cell division.

Polarized Th2 cytokine expression by both mucosal gamma delta and alpha beta T cells

Currently only limited information is available as to why dominant IgA isotype responses are supported by mucosal T cells in effector tissues. To address this issue directly, gamma delta and alpha beta T cells were isolated from the submandibular gland (SMG) of mice as an example of mucosal effector tissues. Freshly isolated CD3+ T cells from this tissue contained relatively high numbers of activated cells [approximately 10% interleukin-2 receptor (IL-2R)+ cells and 15% of cells in cycle stages S and G2 + M], of which 25% and 75% were gamma delta and alpha beta T cells, respectively. The cytokine-specific quantitative reverse transcriptase-polymerase chain reaction and enzyme-linked immunospot analyses revealed that, although both gamma delta and alpha beta T cells were capable of producing an array of Th1 or Th2 cytokines following stimulation via the T cell receptor-CD3 complex, these mucosal T cells were mainly committed to IL-5 and IL-6 expression in vivo (Th2 type). Both freshly isolated gamma delta and alpha beta T cells expressed mRNA and contained IL-5 and IL-6 spot-forming cells (SFC); however, only the latter exhibited high mRNA levels and SFC for a Th1 cytokine (interferon-gamma). Taken together, the results show that freshly isolated CD3+ T cells from SMG contain activated gamma delta and alpha beta T cells which are programmed to produce IL-5 and IL-6. Thus, SMG, an example of an IgA effector tissue, can be characterized as a Th2-dominant site. However, although both gamma delta and alpha beta T cells express cytokine profiles consistent with a Th2 phenotype, only the latter subset with a CD4+ CD8- phenotype provided effective help for mucosal B cell responses in vitro.

Co-expression of CD8 alpha in CD4+ T cell receptor alpha beta + T cells migrating into the murine small intestine epithelial layer

We investigated the surface phenotype of CD3+CD4+ T cell receptor (TCR) alpha beta + T cells repopulating the intestinal lymphoid tissues of C.B-17 scid/scid (severe-combined immunodeficient; scid) (H-2d, Ld+) mice. CD4+ CD8- T cells were cell sorter-purified from various secondary and tertiary lymphoid organs of congenic C.B-17 +/+ (H-2d, Ld+) or semi-syngeneic dm2 (H-2d, Ld-) immunocompetent donor mice. After transfer of 10(5) cells into young scid mice, a mucosa-homing, memory CD44hi CD45RBlo CD4+ T cell population was selectively engrafted. Large numbers of single-positive (SP) CD3+ CD2+ CD28+ CD4+ CD8- T cells that expressed the alpha 4 integrin chain CD49d were found in the spleen, the mesenteric lymph nodes, the peritoneal cavity and the gut lamina propria of transplanted scid mice. Unexpectedly, large populations of donor-type double-positive (DP) CD4+ CD8 alpha + CD8 beta - T cells with high expression of the CD3/TCR complex appeared in the epithelial layer of the small intestine of transplanted scid mice. In contrast to SP CD4+ T cells, the intraepithelial DP T cells showed low expression of the CD2 and the CD28 co-stimulator molecules, and of the alpha 4 integrin chain CD49d, but expressed high levels of the alpha IEL integrin chain CD103. The TCR-V beta repertoire of DP but not SP intraepithelial CD4+ T cells was biased towards usage of the V beta 6 and V beta 8 viable domains. Highly purified populations of SP and DP CD4+ T cell populations from the small intestine epithelial layer of transplanted scid mice had different abilities to repopulate secondary scid recipient mice: SP CD4+ T cells repopulated various lymphoid tissues of the immunodeficient host, while intraepithelial DP CD4+ T cells did not. Hence, a subset of CD3+ CD4+ TCR alpha beta + T cells apparently undergoes striking phenotypic changes when it enters the microenvironment of the small intestine epithelial layer.

Changes in the intestinal lymphoid compartment throughout life: implications for the local generation of intestinal T cells

The intestinal lymphoid compartment has a rather stable composition throughout life. However, both during early neonatal development and at high age unique cell populations can be recognized at distinct sites in the intestinal tissue. Directly after birth all intestinal CD3+ cells are found in the lamina propria. At this time the epithelium does not contain T cells. These CD3+ lamina propria lymphocytes co-express both TCR beta and TCR delta chains, probably reflecting the expression of a TCR beta delta heterodimer on the cell surface. Cells with this particular phenotype are present in comparable numbers in the lamina propria of both neonatal euthymic and athymic mice, indicating the thymus-independent nature of these cells. During aging the frequency of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells increases. These cells are also considered to be thymus-independent. The appearance of high numbers of CD4+ CD8 alpha alpha+ intestinal T cells in aged mice is even more striking. It is postulated that the neonatal TCR beta delta+ cells, and probably also the CD4+ CD8 alpha alpha+ cells as found in old mice, are intermediates in the extrathymic differentiation pathway of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells.