Differential homing mechanisms regulate regionalized effector CD8alphabeta+ T cell accumulation within the small intestine

The CC chemokine receptor (CCR)9 is expressed on the majority of small intestinal, but few colonic, T cells, whereas its ligand CCL25 is constitutively expressed by small intestinal epithelial cells. As such, CCR9/CCL25 have been proposed to play a central role in regulating small intestinal but not colonic immune responses and thus to organize regionalized immunity within the intestinal mucosa. Here, we demonstrate that CCL25 is expressed at reduced levels by epithelial cells in the distal compared with proximal small intestine, which correlated with less efficient CCR9-dependent effector CD8alphabeta+ T cell entry into the ileal epithelium. In vitro-generated alpha4beta7+ effector CD8alphabeta+ T cell entry into the lamina propria was less dependent on CCR9 than entry into the epithelium along the entire length of the small intestine and in particular in the ileum. CCR9-independent alpha4beta7+ effector CD8alphabeta+ T cell entry was pertussis toxin-sensitive, suggesting a role for additional Galpha(I)-linked G protein-coupled receptors. Finally, in vivo-primed effector CD8alphabeta+ T cells displayed regionalized differences in their entry to the small intestinal epithelium with enhanced CCR9-independent entry to the ileum. These results highlight a hitherto underappreciated compartmentalization of immune responses within the small intestine and have direct implications for targeting strategies aimed at regulating T cell localization to the small intestinal mucosa.     

Trafficking machinery of NKT cells: shared and differential chemokine receptor expression among V alpha 24(+)V beta 11(+) NKT cell subsets with distinct cytokine-producing capacity

Natural killer T (NKT) cells are important regulators of the immune system, but their trafficking machinery, including expression of chemokine receptors, has been poorly defined. Unlike other conventional T-cell populations, we show that most NKT cells express receptors for extralymphoid tissue or inflammation-related chemokines (CCR2, CCR5, and CXCR3), while few NKT cells express lymphoid tissue-homing chemokine receptors (CCR7 and CXCR5). A population with homing potential for lymph nodes (L selectin(+) CCR7(+)) exists only within a small subset of CD4 NKT cells. We show differential expression of chemokine receptors among NKT cell subsets: CCR4 is mainly expressed by a high cytokine (interleukin-4/interleukin-2)-producing (CD4) NKT subset, while CCR1, CCR6, and CXCR6 are preferentially expressed by the low cytokine-producing CD8 and CD4(-)CD8(-) subsets. In line with this, TARC/CCL17 (a CCR4 ligand) induces preferential chemotaxis of the CD4 NKT subset, while chemotactic activities of LARC/CCL20 (a CCR6 ligand) and MIP-1 alpha/CCL3 (a CCR1 ligand) are focused on the CD8 and CD4(-)CD8(-) NKT cells. We conclude that, unlike conventional naive, memory, or effector T cells, the entire NKT cell population expresses nonlymphoid tissue homing chemokine receptors, yet NKT cell subsets differ considerably from each other by displaying distinct and reciprocal expression patterns of some chemokine receptors. Our results identify chemokine receptors that are potentially important for trafficking of human blood NKT cell subsets and reveal their function (cytokine production capacity)-dependent differential trafficking potentials.     

Polarized production of T-helper cell type 1 cells in Peyer's patches in Crohn's disease

BACKGROUND/AIMS: Although Peyer's patches (PPs) serve as important antigen-sampling sites for the immune system, surprisingly little attention has been paid to their associations with the onset of Crohn's disease (CD) as antigen entry sites. To examine the immunological events in PPs, we performed functional and phenotypical studies on PP cells, the lamina propria cells in the colonic mucosa and peripheral blood mononuclear cells (PBMC) in inflammatory bowel disease. PATIENTS: The subjects were 9 children and adolescents with active CD, 9 with inactive CD, 11 with active ulcerative colitis (UC), and 22 normal controls. METHODS: The cytokine profile in PPs and lamina propria was performed through Elispot assay and RT-PCR. PP mononuclear cells and PBMC from the subjects were analyzed by flow cytometry using monoclonal antibodies to interferon-gamma and interleukin-4, and CC chemokine receptors (CCR) 4 and 5. RESULTS: Th1 together with Tc1 cells were dominant in PPs in the active phase of CD, but not in inactive CD, UC, or normal controls. They did not actually produce interferon-gamma, however they have abundant mRNA of the cytokine. Substantial levels of CCR5 ligands, MIP-1alpha and RANTES mRNA were found in the inflamed intestinal mucosa in CD. CONCLUSIONS: It is conceivable that PPs in the terminal ileum in CD may initially sample luminal antigens where Th1-type memory cells are activated which migrate to the peripheral intestinal mucosa. Those immunological changes may not be related to the etiology of UC.     

Expression and regulation of the chemokine receptor CXCR3 on lymphocytes from normal and inflammatory bowel disease mucosa

Chemokine receptors play an important role in the recruitment of activated T cells to inflammatory sites. The aim of this study was to analyze the expression of the chemokine receptor CXCR3 on T lymphocytes in intestinal lymphoid tissues and to document the altered disposition of these cells in patients with inflammatory bowel disease (IBD). The expression and regulation of CXCR3 on mucosal lymphoid tissue and peripheral blood lymphocytes (PBLs) were analyzed by flow cytometry and Northern blotting. The migration of lamina propria lymphocytes (LPLs) and PBLs to interferon (IFN)-gamma-inducible protein (IP)-10 (or CXCL10) was evaluated by chemotaxis assays. IFN-gamma and interleukin-4-producing T lymphocytes were quantitated by intracellular staining, and IFN-gamma was measured in culture supernatants by enzyme-linked immunosorbent assay. CXCR3 is expressed on the majority of CD4 lamina propria (LP) T cells and correlates with a T-helper (Th) type 1/Th-0 cytokine phenotype on LP and mesenteric lymph node (MLN) CD4 T lymphocytes. IP-10/CXCL10 is more chemotactic in vitro for both CD4 and CD8 T cells that have been isolated from the LP compared with peripheral blood. CXCR3 protein, but not messenger RNA, expression was lower in inflamed LPLs compared with uninvolved LPLs in patients with ulcerative colitis but not in those with Crohn's disease. However, CXCR3 was expressed on a higher percentage of MLN CD4 T cells isolated from inflamed intestinal tissue, and CXCR3 expression could be induced in vitro with T-cell activation in MLN CD4 T cells. In summary, most CXCR3 T lymphocytes in normal intestinal tissues are Th-1/Th-0 effector/memory cells. Activation-dependent receptor regulation and alteration in receptor-bearing cells, primarily in MLN draining inflamed intestinal tissue, suggest an important role for this T-cell subset in the pathogenesis of human IBD.     

Chemokine receptor repertoire reflects mature T-cell lymphoproliferative disorder clinical presentation

The World Health Organization classification of mature T-cell lymphoproliferative disorders, combines clinical, morphological and immunophenotypic data. The latter is a major contributor to the classification, as well as to the understanding of the malignant T-cell behavior. The fact that T-cell migration is regulated by chemokines should, in theory, enable us to identify tissue tropism and organ involvement by neoplastic T-cells by monitoring chemokine receptor surface expression. To address this issue we compared the expression of several early and late inflammatory, homeostatic, and organ specific chemokine receptors on blood T-cells from normal individuals and patients with T-cell large granular lymphocytic leukemia and peripheral T-cell lymphoma. T-cell large granular lymphocytic leukemia cells mainly express late inflammatory chemokine receptors (CXCR1 and CXCR2), whereas peripheral T-cell lymphoma cells usually express one or more organ homing receptors (CCR4, CCR6 and CCR7). Nevertheless, no clear correlation was found between CCR4 and CCR7 expression and skin and lymph node involvement, respectively. Compared to their normal counterparts, lymphoma T-cells displayed an exaggerated CCR4 expression, whereas leukemic T-cells had abnormally high CXCR1 and CXCR2 expression. Further analysis revealed that, in leukemia patients, the percentage of neoplastic cells expressing CCR5 correlates directly with lymphocytosis. In addition, in the case of CD8 T-cell leukemia patients, an inverse correlation with neutropenia was found. In lymphoma patients, higher CCR4 and CCR7 expression is accompanied by lower to absent CCR5 expression.     

CXCR4 engagement is required for HIV-1-induced L-selectin shedding

The chemokine receptor, CXCR4, serves as the primary coreceptor for entry of T-cell tropic human immunodeficiency virus (HIV). Binding of either the CXC-chemokine, stromal-derived factor 1 alpha (SDF-1 alpha), or a CXCR4 antagonist, AMD3100, to CXCR4 inhibits infection of CD4(+) T cells by T-tropic HIV-1, although only SDF-1 alpha triggers T-cell signaling cascades. We have previously demonstrated that ligation of CD4 by T-cell tropic HIV-1 NL4-3 induces metalloproteinase-dependent L-selectin (CD62L) shedding on resting CD4(+) T cells. However, the role of CXCR4 in HIV-induced L-selectin shedding is unclear. Here, we show that L-selectin shedding induced by HIV-1 NL4-3 is completely reversed by AMD3100, but not SDF-1 alpha, although SDF-1 alpha alone does not induce L-selectin shedding. These results indicate that engagement of both CD4 and CXCR4 is required for HIV-induced shedding of L-selectin on primary resting CD4(+) T cells.     

Altered expression of the receptor-ligand pair CXCR5/CXCL13 in B cells during chronic HIV-1 infection

HIV-1 infection is associated with B-cell abnormalities, such as hypergammaglobulinemia, poor immunization responses, and loss of serologic memory. To determine whether altered expression of chemokine receptors and their ligands may play a role in B-cell dysfunctions during HIV-1 infection, the expression of CXC chemokine receptor 4 (CXCR4), CXCR5, and CC chemokine receptor 7 (CCR7) and their respective ligands on CD19(+) B cells were examined in HIV-1-infected patients and controls. We report a decreased CXCR5 expression on B cells from patients (P < .05), a phenomenon associated with a low CD4 T-cell count (< 350 cells/microL). Interestingly, an increased expression of CXC chemokine ligand 13 (CXCL13), the ligand for CXCR5, was found in peripheral B cells from HIV-1-infected patients. Moreover, on B-cell activation in vitro, CXCL13 was secreted in culture. CXCL13(+) B cells were also found in the lymph nodes of HIV-1-infected patients, but not in control tissue. B-cell migration toward CXCL13, CXCL12, and CC chemokine ligand 21 (CCL21), ligands for CXCR5, CXCR4, and CCR7 was also evaluated. In patients with a low CD4 T-cell count, migration toward all ligands was increased. Our findings indicate that altered expression of the chemokine receptor-ligand pair, CXCR5/CXCL13, may participate in the establishment of B-cell dysfunctions during HIV-1 infection.     

CD4+NKG2D+ T cells in Crohn's disease mediate inflammatory and cytotoxic responses through MICA interactions

BACKGROUND & AIMS: Crohn's disease (CD) is an inflammatory bowel disease characterized by uncontrolled immune responses to bacterial flora, with excessive activation of T lymphocytes. MICA is a stress-induced major histocompatibility complex-related molecule expressed on normal intestinal epithelial cells (IECs) and recognized by the NKG2D-activating receptor on CD8(+) T cells, gammadelta T cells, and natural killer cells. We examined the role of MICA-NKG2D interactions in the activation of T lymphocytes in CD. METHODS: MICA expression was analyzed by flow cytometry on IECs isolated from patients with active inflammatory bowel disease and controls. NKG2D expression and function were analyzed on lamina propria and peripheral blood lymphocytes. RESULTS: MICA expression was significantly increased on IECs in CD, with higher expression in macroscopically involved areas. A subset of CD4(+) T cells expressing NKG2D was increased in the lamina propria from patients with CD compared with controls and patients with ulcerative colitis. CD4(+)NKG2D(+) T cells with a Th1 cytokine profile and expressing perforin were increased in the periphery and in the mucosa in CD. CD4(+)NKG2D(+) T-cell clones were functionally active through MICA-NKG2D interactions, producing interferon-gamma and killing targets expressing MICA. IECs from patients with CD had the ability to expand this subset in vitro. CD4(+)NKG2D(+) lamina propria lymphocytes from patients with CD highly expressed interleukin-15R alpha, and interleukin-15 increased NKG2D and DAP10 expression in CD4(+)NKG2D(+) T-cell clones. CONCLUSIONS: These findings highlight the role of MICA-NKG2D in the activation of a unique subset of CD4(+) T cells with inflammatory and cytotoxic properties in CD.     

Mucosal T-cell function.

Lymphocytes in the intestinal lamina propria probably differ from lymphocyte populations in the circulation or in other tissue sites in a number of ways. First, lamina propria lymphocytes are phenotypically distinct in that few of these cells normally express the Leu-8 or CD45RA antigens. The presence of these molecules on CD4 T cells correlates with suppressor and suppressor-inducer function, and therefore the majority of CD4 T cells in the intestinal lamina propria have the phenotype associated with high helper activity. A substantial proportion of lamina propria lymphocytes also have evidence of activation, based on expression of the IL-2R alpha chain and HLA-DR molecules. Lymphocytes in the intestinal lamina propria are different in their potential for expression of lymphokine gene products, because activated cells from the lamina propria have high expression of mRNA for IL-2, IL-4, IL-5, and IFN-gamma in comparison to circulating lymphocytes. Mesenteric lymph node T cells also differ from circulating lymphocytes in their high expression of IL-4 and IL-5 mRNA. A further difference between mesenteric lymph node and lamina propria T cells is that the former can proliferate in response to IL-4, whereas the latter cannot. These phenotypic and mRNA differences of lamina propria lymphocytes also correlate well with their high helper activity in vitro for immunoglobulin synthesis in the pokeweed mitogen system. T cells with the potential for cytolytic activity are present in the intestinal lamina propria, although there is no definitive evidence that they are cytolytically active under physiologic or pathologic conditions. Finally, in a model system of intestinal inflammation, lymphogranuloma venereum in nonhuman primates, lamina propria T cells at the site of inflammation were unable to respond to specific antigens with proliferation but did respond with high helper activity. These observations are all consistent with the conclusion that T cells in the lamina propria are pleomorphic but are highly enriched for subpopulations of activated memory cells that are geared for effector functions such as helper and cytolytic functions. These functions are likely to be critical in maintaining normal host defense in the mucosal environment.     

Prostaglandin E2 synergistically with interleukin-23 favors human Th17 expansion

Microenvironment molecular cues direct T helper (Th) cell differentiation; however, Th17 fate determination is still imprecisely understood in humans. To assess the role of prostaglandin E(2) (PGE(2)) in Th expansion, we activated peripheral blood mononuclear cells by CD3 cross-linking. In the presence of exogenous PGE(2), peripheral blood mononuclear cells produced higher interleukin-17 (IL-17), C-C chemokine ligand 20 (CCL20)/macrophage inflammatory protein 3alpha (MIP-3alpha), CXC chemokine ligand 8 (CXCL8)/IL-8, and lower interferon-gamma and IL-22 levels than in control cultures. Exogenous PGE(2) and IL-23 synergized in inducing IL-17, whereas indomethacin and IL-23 blockade drastically reduced IL-17 but not interferon-gamma production. Furthermore, IL-1 but not tumor necrosis factor was absolutely required for IL-17 production. PGE(2) doubled the frequency of CD4+ T cells producing IL-17 and within the CD4+ subset enhanced C-C chemokine receptor 6 (CCR6) and CCR4 while decreasing CXC chemokine receptor 3 (CXCR3) expression. Furthermore, in CD4+ T-cell lines, the production of IL-17 segregated with the CCR6+ subset. In the presence of CCR6+ compared with CXCR3+ Th cells, monocytes/macrophages produced much higher levels of matrix metalloproteinase-1, -3, and -9 but similar levels of CXCL10 and IL-1beta. These results identify PGE(2) and IL-23 as participating in the expansion of CD4+ T cells endowed with high IL-17 production capacity, which in turn favors monocyte production of mediators important for host defense and tissue destruction.     

Reduced chemokine receptor 9 on intraepithelial lymphocytes in celiac disease suggests persistent epithelial activation

BACKGROUND & AIMS: Celiac disease is caused by an inappropriate immune response to dietary gluten, with increased epithelial lymphocyte infiltration in the duodenum/jejunum as a hallmark. The chemokine receptor 9 (CCR9) is a small intestinal homing receptor normally found on most mucosal T cells in this organ. Because CCR9 expression appears to be activation dependent, we examined CCR9 on duodenal T cells from untreated and treated (gluten-free diet) patients with celiac disease and healthy controls. METHODS: Duodenal biopsy specimens and blood samples were obtained for histologic analysis and flow-cytometric CCR9 analysis of isolated lymphocytes. CCR9 expression after activation was studied in peripheral blood T cells from healthy volunteers. RESULTS: The median number of CCR9(+) cells among CD3(+) T cells in epithelium and lamina propria, respectively, was 56% and 48% in controls, 11% and 40% in treated patients, and 1% and 8% in untreated patients. Significant differences occurred between controls and treated or untreated patients in the epithelium but only between controls and untreated patients in the lamina propria (P=.008, all comparisons). No such differences were seen in peripheral blood, but stimulation with phorbol myristate acetate and ionomycin and, to a lesser extent, stimulation via NKG2D reduced the CCR9 expression on blood T cells. CONCLUSIONS: CCR9 expression is reduced on epithelial and lamina propria T cells in untreated celiac disease. Down-regulation of CCR9 persists in intraepithelial T cells from well-treated patients. This suggests ongoing immune activation preferentially within the epithelium.     

Increased adhesion molecule and chemokine receptor expression on CD8+ T cells trafficking to cerebrospinal fluid in HIV-1 infection

BACKGROUND: The central nervous system (CNS) is a recognized target for human immunodeficiency virus type 1 (HIV-1). CD8(+) T cells may mediate viral clearance from the CNS but also may contribute to immune-mediated neuronal damage. METHODS: Using 4- and 6-color flow cytometry, we investigated the role of adhesion molecules (very late antigen [VLA]-4 [ alpha 4 beta 1 integrin] and leukocyte function antigen [LFA]-1 [ alpha L beta 2 integrin]) and chemokine receptors (CXCR3 and CCR5) in CD8(+) T cell migration to cerebrospinal fluid (CSF) during HIV-1 infection. RESULTS: CD8(+) T cells trafficking to CSF were uniformly VLA-4(high), LFA-1(high). CCR5 expression was significantly enhanced in T cells from CSF, compared with those from blood (P<.001), including HIV-1-specific CD8(+) T cells, and most T cells from CSF expressed both CXCR3 and CCR5. Interferon-inducible protein (IP)-10 (CXCL10) levels in CSF were significantly increased in HIV-1-positive individuals, relative to IP-10 levels in control subjects (P=.007), and a positive correlation was found between IP-10 levels and virus load in CSF (r2=.777; P=.0007). CONCLUSIONS: These findings suggest that LFA-1, CCR5 and CXCR3, and IP-10 play an important role in lymphocyte trafficking to CSF during HIV-1 infection. These observations suggest a "push-pull" model, in which lymphocyte extravasation is driven by lymphocyte activation, expression of adhesion molecules, and increased vascular permeability and is coupled with chemokine-mediated trafficking to inflammatory sites in the CNS.     

Inhibition of HIV-1 replication by GB virus C infection through increases in RANTES, MIP-1alpha, MIP-1beta, and SDF-1

Background People coinfected with HIV and GB virus C (GBV-C) have lower mortality than HIV-positive individuals without GBV-C infection. HIV uses either of the chemokine receptors CCR5 and CXCR4 for entry into CD4-positive cells. Longer survival in HIV-positive individuals is associated with high serum concentrations of ligands for CCR5 (RANTES [regulated on activation, normal T-cell expressed and secreted] and macrophage inflammatory proteins [MIP] 1alpha and 1beta) and CXCR4 (stromal-derived factor [SDF-1]), and with decreased expression of CCR5 on lymphocytes. Methods Peripheral-blood mononuclear cells were coinfected with GBV-C and HIV, and HIV replication was monitored by measuring infectivity and HIV p24 antigen production. Chemokine secretion was measured by ELISA, chemokine-receptor expression by flow cytometry, and cellular chemokine mRNA expression by differential hybridisation. Findings GBV-C infection of peripheral-blood mononuclear cells resulted in decreased replication of both clinical and laboratory HIV strains that use either CCR5 or CXCR4 as their coreceptor. Inhibition was related to the dose and timing of the GBV-C infection. Expression of mRNA for RANTES, MIP-1alpha, MIP-1beta, and SDF-1 and secretion of the chemokines into culture supernatants were higher in GBV-C-infected cells than in mock-infected cells. The inhibitory effect of GBV-C on HIV replication was blocked by incubation with neutralising antibodies against the relevant chemokines, and surface expression of CCR5 was significantly lower in GBV-C-infected cells than in mock-infected cells. Interpretation GBV-C induces HIV-inhibitory chemokines and reduces expression of the HIV coreceptor CCR5 in vitro. This study provides insight into the epidemiological association between GBV-C infection and longer survival in HIV-infected individuals.     

Anti-CD3 preconditioning separates GVL from GVHD via modulating host dendritic cell and donor T-cell migration in recipients conditioned with TBI

Host dendritic cells (DCs) play a critical role in initiating graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL), and separation of GVL from GVHD remains a major challenge in the treatment of hematologic malignancies by allogeneic hematopoietic cell transplantation (HCT). Here, we show that preconditioning with anti-CD3 monoclonal antibody before conditioning with total body irradiation (TBI) prevents GVHD but retains GVL in a HCT model of major histocompatibility complex (MHC)-mismatched C57BL/6 donor to BALB/c host. Prevention of GVHD is associated with inhibition of donor T-cell expression of homing and chemokine receptors, and inhibition of GVHD target tissue expression of chemokines. Furthermore, inhibition of donor T-cell expression of gut homing alpha4beta7 and chemokine receptor (CCR)9 by anti-CD3 preconditioning results from a reduction of CD103(+) DCs in draining mesenteric lymph nodes (LNs), which is associated with down-regulation of DC expression of CCR7, a receptor required for tissue DC migration to draining LNs. These results indicate that anti-CD3 preconditioning reduces not only tissue release of chemokines but also prevents tissue DC migration to draining LNs and subsequently reduces the capacity of DCs of draining LNs to imprint donor T-cell tissue tropism. Therefore, modulation of host DCs by anti-CD3 preconditioning before HCT represents a new approach for separating GVL from GVHD.     

An immunodominant DQ8 restricted gliadin peptide activates small intestinal immune response in in vitro cultured mucosa from HLA-DQ8 positive but not HLA-DQ8 negative coeliac patients

BACKGROUND: Studies on intestinal T cell clones from the mucosa of patients with coeliac disease have led to the identification of immunogenic gliadin epitopes. One is HLA-DQ8 restricted, its recognition by T cells being increased by introduction of negatively charged residues operated by tissue transglutaminase. AIM: To test HLA-DQ8 restricted epitope in both native (QYPSGQGSFQPSQQNPQA) and deamidated (QYPSGEGSFQPSQENPQA) forms in an organ culture system of treated coeliac mucosa from HLA-DQ8 positive and HLA-DQ8 negative patients. PATIENTS AND METHODS: Jejunal biopsies obtained from 10 patients with coeliac disease (six HLA-DQ8 positive and four HLA-DQ8 negative) were cultured in vitro with a peptic-tryptic digest (PT) of gliadin, or with the native (peptide A) or deamidated (peptide B) peptide. Intraepithelial CD3(+) and lamina propria total CD25(+) and CD3(+)CD25(+) cells were counted, lamina propria intercellular adhesion molecule 1 (ICAM-1) expression was evaluated, as well as that of Fas molecules on epithelial cells. RESULTS: In HLA-DQ8 positive, but not in HLA-DQ8 negative, coeliacs the density of intraepithelial CD3(+) cells, lamina propria total CD25(+), and CD3(+)CD25(+) cells, as well as expression of ICAM-1 and Fas molecules were significantly increased in biopsies cultured with PT, peptide A, or peptide B compared with biopsies cultured in medium alone. CONCLUSION: These data show that the DQ8 restricted gliadin peptide is immunogenic only in the intestinal mucosa of HLA-DQ8 positive coeliac patients in both native and deamidated forms.