The B subunit of Escherichia coli heat‐labile toxin alters the development and antigen‐presenting capacity of dendritic cells

Escherichia coli's heat‐labile enterotoxin (Etx) and its non‐toxic B subunit (EtxB) have been characterized as adjuvants capable of enhancing T cell responses to co‐administered antigen. Here, we investigate the direct effect of intravenously administered EtxB on the size of the dendritic and myeloid cell populations in spleen. EtxB treatment appears to enhance the development and turnover of dendritic and myeloid cells from precursors within the spleen. EtxB treatment also gives a dendritic cell (DC) population with higher viability and lower activation status based on the reduced expression of MHC‐II, CD80 and CD86. In this respect, the in vivo effect of EtxB differs from that of the highly inflammatory mediator lipopolysaccharide. In in vitro bone marrow cultures, EtxB treatment was also found to enhance the development of DC from precursors dependent on Flt3L. In terms of the in vivo effect of EtxB on CD4 and CD8 T cell responses in mice, the interaction of EtxB directly with DC was demonstrated following conditional depletion of CD11c⁺ DC. In summary, all results are consistent with EtxB displaying adjuvant ability by enhancing the turnover of DC in spleen, leading to newly mature myeloid and DC in spleen, thereby increasing DC capacity to perform as antigen‐presenting cells on encounter with T cells.     

Brucella abortus induces intracellular retention of MHC‐I molecules in human macrophages down‐modulating cytotoxic CD8+ T cell responses

Brucella abortus elicits a vigorous Th1 immune response which activates cytotoxic T lymphocytes. However, B. abortus persists in its hosts in the presence of CD8⁺ T cells, establishing a chronic infection. Here, we report that B. abortus infection of human monocytes/macrophages inhibited the IFN‐γ‐induced MHC‐I cell surface expression. This phenomenon was dependent on metabolically active viable bacteria. MHC‐I down‐modulation correlated with the development of diminished CD8⁺ cytotoxic T cell response as evidenced by the reduced expression of the activation marker CD107a on CD8⁺ T lymphocytes and a diminished percentage of IFN‐γ‐producing CD8⁺ T cells. Inhibition of MHC‐I expression was not due to changes in protein synthesis. Rather, we observed that upon B. abortus infection MHC‐I molecules were retained within the Golgi apparatus. Overall, these results describe a novel mechanism based on the intracellular sequestration of MHC‐I molecules whereby B. abortus would avoid CD8⁺ cytotoxic T cell responses, evading their immunological surveillance.     

Expression of PD‐1/LAG‐3 and cytokine production by CD4+ T cells during infection with Plasmodium parasites

CD4⁺ T cells play critical roles in protection against the blood stage of malarial infection; however, their uncontrolled activation can be harmful to the host. In this study, in which rodent models of Plasmodium parasites were used, the expression of inhibitory receptors on activated CD4⁺ T cells and their cytokine production was compared with their expression in a bacterial and another protozoan infection. CD4⁺ T cells from mice infected with P. yoelii 17XL, P yoelii 17XNL, P. chabaudi, P. vinckei and P. berghei expressed the inhibitory receptors, PD‐1 and LAG‐3, as early as 6 days after infection, whereas those from either Listeria monocytogenes‐ or Leishmania major‐infected mice did not. In response to T‐cell receptor stimulation, CD4⁺ T cells from mice infected with all the pathogens under study produced high concentrations of IFN‐γ. IL‐2 production was reduced in mice infected with Plasmodium species, but not in those infected with Listeria or Leishmania. In vitro blockade of the interaction between PD‐1 and its ligands resulted in increased IFN‐γ production in response to Plasmodium antigens, implying that PD‐1 expressed on activated CD4⁺ T cells actively inhibits T cell immune responses. Studies using Myd88^?/?, Trif^?/? and Irf3^?/? mice showed that induction of these CD4⁺ T cells and their ability to produce cytokines is largely independent of TLR signaling. These studies suggest that expression of the inhibitory receptors PD‐1 and LAG‐3 on CD4⁺ T cells and their reduced IL‐2 production are common characteristic features of Plasmodium infection.

     

Gatekeeper role of brain antigen‐presenting CD11c+ cells in neuroinflammation

Multiple sclerosis is the most frequent chronic inflammatory disease of the CNS. The entry and survival of pathogenic T cells in the CNS are crucial for the initiation and persistence of autoimmune neuroinflammation. In this respect, contradictory evidence exists on the role of the most potent type of antigen‐presenting cells, dendritic cells. Applying intravital two‐photon microscopy, we demonstrate the gatekeeper function of CNS professional antigen‐presenting CD11c⁺ cells, which preferentially interact with Th17 cells. IL‐17 expression correlates with expression of GM‐CSF by T cells and with accumulation of CNS CD11c⁺ cells. These CD11c⁺ cells are organized in perivascular clusters, targeted by T cells, and strongly express the inflammatory chemokines Ccl5, Cxcl9, and Cxcl10. Our findings demonstrate a fundamental role of CNS CD11c⁺ cells in the attraction of pathogenic T cells into and their survival within the CNS. Depletion of CD11c⁺ cells markedly reduced disease severity due to impaired enrichment of pathogenic T cells within the CNS.     

Age-related changes in the distribution and frequency of myeloid and T cell populations in the small intestine of calves

Mucosal dendritic cells (DCs) play a key role in discriminating between dietary antigens, commensal microflora and pathogens but little is known regarding age-related changes in mucosal DC populations. We analyzed lymphoid and myeloid populations within the epithelium and lamina propria (LP) of the ileum and jejunum of weaned calves (6 months old) and compared their frequency and distribution with newborn calves (3–5 weeks old). CD4, CD8 and γδ TcR T cells and CD11c^HiMHC Class II⁺ myeloid cell frequency were significantly different when comparing ileum and jejunum of weaned calves. In particular, the number of CD8 and γδ TcR T cells, and CD11c^HiCD14⁺ macrophages was significantly greater in the ileum but CD11c⁺ and CD11b⁺ myeloid cell distribution was similar throughout the mucosal epithelium of the small intestine. Furthermore, significant age-related changes were apparent when comparing the frequency and abundance of mucosal leukocyte subpopulations in newborn and weaned calves. Total mucosal leukocytes (CD45⁺) increased significantly with age in both ileum and jejunum and much of this increase was attributed to mucosal T cells (CD3⁺). In particular, CD4 T cells and NK cells increased significantly in the jejunum and CD8, and γδ TcR T cells increased significantly with age throughout the small intestine. In contrast, CD11c^HiMHC Class II⁺ myeloid cells remained numerically unchanged with age but DCs (CD13⁺, CD26⁺, CD205⁺) were enriched and macrophages (CD14⁺, CD172a⁺) were depleted in older animals. Therefore, regional differences between ileal and jejunal mucosal leukocytes changed with age and there was also a marked age-dependent change in the composition of mucosal myeloid cells. These observations have significant implications for host responses to both pathogens and commensal microflora.     

Altered frequency of CD8+CD11c+ T cells and expression of immunosuppressive molecules in lymphoid organs of mouse model of colorectal cancer

CD11c is a member of the β2-integrin family typically used to define myeloid dendritic cells (DCs). Recent reports identify CD11c-expressing CD8⁺ T cells as a new subset of CD8⁺ regulatory T cells (Treg). Evidence exists that CD11c⁺CD8⁺ T cells may exert their effector or regulatory functions under different conditions. To date, no studies have addressed the frequency of CD11c⁺ T cells in cancer. Limited evidence exists in terms of expression of immune-checkpoint receptors, programmed cell death protein 1 (PD-1) and T-lymphocyte-associated antigen 4 (CTLA-4), as well as forkhead box P3 (Foxp3) in mouse lymphoid organs. Here, we have assessed CD11c⁺CD8⁺ and CD11c⁺CD4⁺ T cells, Foxp3, PD-1, and CTLA-4 expressing CD4⁺ T cells and CD8⁺ T cells in different tissues from three groups of male BALB/c mice—young, mature, and those with colorectal cancer (CRC). Analysis of CD3⁺CD11c⁺ T cells in the bone marrow (BM), spleen, and lymph nodes (LN) in each group showed a higher percentage of CD3⁺CD11c⁺ T cells in the BM from all groups and in the lymphoid organs of the cancer group compared with the young and mature groups. CD4^low and CD4^high cell fractions in mice BM have different expression patterns for Foxp3 and CTLA-4. We have observed a higher frequency of CD8⁺PD-1⁺ T cells in the BM, spleen, and LN of CRC mice compared with normal mice. T-cell exhaustion is associated with inhibitory receptor PD-1. According to the regulatory roles of CD11c expression in CD8⁺ T cells, we have proposed that the elevated percentage of CD11c, Foxp3, CTLA-4, and PD-1 expressing T cells were associated with immune response dysregulation in CRC.     

Resistance to Intranasal Infection with Balamuthia mandrillaris Amebae is T‐Cell Dependent

T and B cell‐deficient BALB/c SCID mice become severely ill and die of amebic encephalitis after intranasal infection with Balamuthia mandrillaris, while adult immunocompetent BALB/c wild‐type (WT) mice are resistant. To further investigate the role of lymphocytes in protection from Balamuthia amebic encephalitis (BAE), SCID mice were reconstituted with and WT mice selectively depleted of lymphocytes before infection. Reconstitution of SCID mice with whole spleen cells from WT mice rendered the recipients as resistant to BAE as WT mice. SCID mice that had received spleen cells depleted of CD4⁺ T cells remained susceptible. When adult WT mice were depleted of both CD4⁺ and CD8⁺ T cells or of CD4⁺ T cells alone, these mice also became susceptible to BAE. Depletion of CD8⁺ T cells alone increased susceptibility only marginally. All morbidity and mortality data were underpinned by histological analysis of the brain.     

Post-Spaceflight (STS-135) Mouse Splenocytes Demonstrate Altered Activation Properties and Surface Molecule Expression

Alterations in immune function have been documented during or post-spaceflight and in ground based models of microgravity. Identification of immune parameters that are dysregulated during spaceflight is an important step in mitigating crew health risks during deep space missions. The in vitro analysis of leukocyte activity post-spaceflight in both human and animal species is primarily focused on lymphocytic function. This report completes a broader spectrum analysis of mouse lymphocyte and monocyte changes post 13 days orbital flight (mission STS-135). Analysis includes an examination in surface markers for cell activation, and antigen presentation and co-stimulatory molecules. Cytokine production was measured after stimulation with T-cell mitogen or TLR-2, TLR-4, or TLR-5 agonists. Splenocyte surface marker analysis immediate post-spaceflight and after in vitro culture demonstrated unique changes in phenotypic populations between the flight mice and matched treatment ground controls. Post-spaceflight splenocytes (flight splenocytes) had lower expression intensity of CD4⁺CD25⁺ and CD8⁺CD25⁺ cells, lower percentage of CD11c⁺MHC II⁺ cells, and higher percentage of CD11c⁺MHC I⁺ populations compared to ground controls. The flight splenocytes demonstrated an increase in phagocytic activity. Stimulation with ConA led to decrease in CD4⁺ population but increased CD4⁺CD25⁺ cells compared to ground controls. Culturing with TLR agonists led to a decrease in CD11c⁺ population in splenocytes isolated from flight mice compared to ground controls. Consequently, flight splenocytes with or without TLR-agonist stimulation showed a decrease in CD11c⁺MHC I⁺, CD11c⁺MHC II⁺, and CD11c⁺CD86⁺ cells compared to ground controls. Production of IFN-γ was decreased and IL-2 was increased from ConA stimulated flight splenocytes. This study demonstrated that expression of surface molecules can be affected by conditions of spaceflight and impaired responsiveness persists under culture conditions in vitro.     

High‐dose wogonin exacerbates DSS‐induced colitis by up‐regulating effector T cell function and inhibiting Treg cell

Wogonin exerts anti‐tumour activities via multiple mechanisms. We have identified that high‐dose wogonin (50 or 100 mg/kg) could inhibit the growth of transplanted tumours by directly inducing tumour apoptosis and promoting DC, T and NK cell recruitment into tumour tissues to enhance immune surveillance. However, wogonin (20–50 μM) ex vivo prevents inflammation by inhibiting NF‐κB and Erk signalling of macrophages and epithelial cells. It is elusive whether high‐dose wogonin promotes or prevents inflammation. To investigate the effects of high‐dose wogonin on murine colitis induced by dextran sodium sulphate (DSS), mice were co‐treated with DSS and various doses of wogonin. Intraperitoneal administration of wogonin (100 mg/kg) exacerbated DSS‐induced murine colitis. More CD4⁺ CD44⁺ and CD8⁺ CD44⁺ cells were located in the inflamed colons in the wogonin (100 mg/kg) treatment group than in the other groups. Frequencies of CD4⁺ CD25⁺ CD127^? and CD4⁺ CD25⁺ Foxp3⁺ cells in the colons and spleen respectively, were reduced by wogonin treatment. Ex vivo stimulations with high‐dose wogonin (50–100 μg/ml equivalent to 176–352 μM) could synergize with IL‐2 to promote the functions of CD4⁺ and CD8⁺ cells. However, regulatory T cell induction was inhibited. Wogonin stimulated the activation of NF‐κB and Erk but down‐regulated STAT3 phosphorylation in the CD4⁺ T cells. Wogonin down‐regulated Erk and STAT3‐Y705 phosphorylation in the regulatory T cells but promoted NF‐κB and STAT3‐S727 activation. Our study demonstrated that high‐dose wogonin treatments would enhance immune activity by stimulating the effector T cells and by down‐regulating regulatory T cells.     

CD1d‐mediated activation of group 3 innate lymphoid cells drives IL‐22 production

Innate lymphoid cells (ILCs) are a heterogeneous family of immune cells that play a critical role in a variety of immune processes including host defence against infection, wound healing and tissue repair. Whether these cells are involved in lipid‐dependent immunity remains unexplored. Here we show that murine ILCs from a variety of tissues express the lipid‐presenting molecule CD1d, with group 3 ILCs (ILC3s) showing the highest level of expression. Within the ILC3 family, natural cytotoxicity triggering receptor (NCR)^?CCR6⁺ cells displayed the highest levels of CD1d. Expression of CD1d on ILCs is functionally relevant as ILC3s can acquire lipids in vitro and in vivo and load lipids on CD1d to mediate presentation to the T‐cell receptor of invariant natural killer T (iNKT) cells. Conversely, engagement of CD1d in vitro and administration of lipid antigen in vivo induce ILC3 activation and production of IL‐22. Taken together, our data expose a previously unappreciated role for ILCs in CD1d‐mediated immunity, which can modulate tissue homeostasis and inflammatory responses.     

The beta2 integrin CD11c distinguishes a subset of cytotoxic pulmonary T cells with potent antiviral effects in vitro and in vivo

Background

The integrin CD11c is known as a marker for dendritic cells and has recently been described on T cells following lymphotropic choriomeningitis virus infection, a systemic infection affecting a multitude of organs. Here, we characterise CD11c bearing T cells in a murine model of localised pulmonary infection with respiratory syncytial virus (RSV).

Methods

Mice were infected intranasally with RSV and expression of β2 integrins and T lymphocyte activation markers were monitored by flow cytometry. On day 8 post RSV infection CD11c⁺ CD8⁺ and CD11c^- CD8⁺ T cells were assessed for cytokine production, cytotoxic activity and migration. Expression of CD11c mRNA in CD8⁺ T cells was assessed by quantitative PCR.

Results

Following RSV infection CD11c⁺ CD8⁺ T cells were detectable in the lung from day 4 onwards and accounted for 45.9 ± 4.8% of CD8⁺ T cells on day 8 post infection, while only few such cells were present in mediastinal lymph nodes, spleen and blood. While CD11c was virtually absent from CD8⁺ T cells in the absence of RSV infection, its mRNA was expressed in CD8⁺ T cells of both naïve and RSV infected mice. CD11c⁺, but not CD11c^-, CD8⁺ T cells showed signs of recent activation, including up-regulation of CD11a and expression of CD11b and CD69 and were recruited preferentially to the lung. In addition, CD11c⁺ CD8⁺ T cells were the major subset responsible for IFNγ production, induction of target cell apoptosis in vitro and reduction of viral titres in vivo.

Conclusion

CD11c is a useful marker for detection and isolation of pulmonary antiviral cytotoxic T cells following RSV infection. It identifies a subset of activated, virus-specific, cytotoxic T cells that exhibit potent antiviral effects in vivo.     

Characterization of age‐associated exhausted CD8+ T cells defined by increased expression of Tim‐3 and PD‐1

Aging is accompanied by altered T‐cell responses that result in susceptibility to various diseases. Previous findings on the increased expression of inhibitory receptors, such as programmed cell death protein 1 (PD‐1), in the T cells of aged mice emphasize the importance of investigations into the relationship between T‐cell exhaustion and aging‐associated immune dysfunction. In this study, we demonstrate that T‐cell immunoglobulin mucin domain‐3 (Tim‐3), another exhaustion marker, is up‐regulated on aged T cells, especially CD8⁺ T cells. Tim‐3‐expressing cells also produced PD‐1, but Tim‐3⁺PD‐1⁺ CD8⁺ T cells had a distinct phenotype that included the expression of CD44 and CD62L, from Tim‐3^?PD‐1⁺ cells. Tim‐3⁺PD‐1⁺ CD8⁺ T cells showed more evident properties associated with exhaustion than Tim‐3^?PD‐1⁺ CD8⁺ T cells: an exhaustion‐related marker expression profile, proliferative defects following homeostatic or TCR stimulation, and altered production of cytokines. Interestingly, these cells produced a high level of IL‐10 and induced normal CD8⁺ T cells to produce IL‐10, which might contribute to immune dysregulation in aged mice. The generation of Tim‐3‐expressing CD8⁺ T cells in aged mice seems to be mediated by encounters with antigens but not by specific infection, based on their high expression of CD49d and their unbiased TCR Vβ usage. In conclusion, we found that a CD8⁺ T‐cell population with age‐associated exhaustion was distinguishable by its expression of Tim‐3. These results provide clues for understanding the alterations that occur in T‐cell populations with age and for improving dysfunctions related to the aging of the immune system.     

口服维生素D对实验性脑疟小鼠树突状细胞的影响

维生素D（VD）为固醇类衍生物,除发挥抗佝偻病作用,还具有一定的免疫调节功能。主要研究VD对实验性脑疟小鼠树突状细胞的影响。结果显示,与对照组相比,在伯氏疟原虫（P.bANKA）感染前给予VD,可降低C57BL/6小鼠发生脑型疟疾的风险,存活时间明显延长。VD预处理后,脾脏中髓样树突状细胞（CD11c⁺CD11b⁺）和浆样树突状细胞（CD11c⁺B220⁺）百分率明显降低,CD11c⁺MHCII⁺细胞、CD11c⁺TLR4⁺细胞和CD11c⁺TLR9⁺细胞的百分含量也显著减少。由此提示,预防性口服VD可抑制感染小鼠树突状细胞的数量和功能,对脑型疟疾的发生具有一定预防作用,为新型抗疟药物的研发提供参考。     

Identification of HLA‐A*11:01‐restricted Mycobacterium tuberculosis CD8+ T cell epitopes

New vaccines are needed to combat Mycobacterium tuberculosis (MTB) infections. The currently employed Bacillus Calmette‐Guérin vaccine is becoming ineffective, due in part to the emergence of multidrug‐resistant tuberculosis (MDR‐TB) strains and the reduced immune capacity in cases of HIV coinfection. CD8⁺ T cells play an important role in the protective immunity against MTB infections, and the identification of immunogenic CD8⁺ T cell epitopes specific for MTB is essential for the design of peptide‐based vaccines. To identify CD8⁺ T cell epitopes of MTB proteins, we screened a set of 94 MTB antigens for HLA class I A*11:01‐binding motifs. HLA‐A*11:01 is one of the most prevalent HLA molecules in Southeast Asians, and definition of T cell epitopes it can restrict would provide significant coverage for the Asian population. Peptides that bound with high affinity to purified HLA molecules were subsequently evaluated in functional assays to detect interferon‐γ release and CD8⁺ T cell proliferation in active pulmonary TB patients. We identified six novel epitopes, each derived from a unique MTB antigen, which were recognized by CD8⁺ T cells from active pulmonary TB patients. In addition, a significant level of epitope‐specific T cells could be detected ex vivo in peripheral blood mononuclear cells from active TB patients by an HLA‐A*11:01 dextramer carrying the peptide Rv3130c_194‐204 (from the MTB triacylglycerol synthase Tgs1), which was the most frequently recognized epitope in our peptide library. In conclusion, this study identified six dominant CD8⁺ T cell epitopes that may be considered potential targets for subunit vaccines or diagnostic strategies against TB.     

Simultaneous color‐coded imaging to distinguish cancer “stem‐like” and non‐stem cells in the same tumor

In this study, we demonstrate that the differential behavior, including malignancy and chemosensitivity, of cancer stem‐like and non‐stem cells can be simultaneously distinguished in the same tumor in real time by color‐coded imaging. CD133⁺ Huh‐7 human hepatocellular carcinoma (HCC) cells were considered as cancer stem‐like cells (CSCs), and CD133^? Huh‐7 cells were considered as non‐stem cancer cells (NSCCs). CD133⁺ cells were isolated by magnetic bead sorting after Huh‐7 cells were genetically labeled with green fluorescent protein (GFP) or red fluorescent protein (RFP). In this scheme, CD133⁺ cells were labeled with GFP and CD133^? cells were labeled with RFP. CSCs had higher proliferative potential compared to NSCCs in vitro. The same number of GFP CSCs and the RFP NSCCs were mixed and injected subcutaneously or in the spleen of nude mice. CSCs were highly tumorigenic and metastatic as well as highly resistant to chemotherapy in vivo compared to NSCCs. The ability to specifically distinguish stem‐like cancer cells in vivo in real time provides a visual target for prevention of metastasis and drug resistance. J. Cell. Biochem. 111: 1035–1041, 2010. © 2010 Wiley‐Liss, Inc.     

Development of peritoneal macrophage along a dendritic cell lineage in response to uptake of oligomannose-coated liposomes

In this study, we investigate the potential of peritoneal macrophages to differentiate into dendritic cell (DCs) in response to preferential uptake of oligomannose-coated liposomes (OMLs). About 30% of peritoneal cells (PECs) preferentially took up OMLs that were administered into the peritoneal cavity. The OML-ingesting cells expressed CD11b and F4/80, but lacked CD11c expression, indicating that the OML-ingesting PECs with a CD11b^highCD11c⁻ phenotype are resident peritoneal macrophages. During in vitro cultivation, CD11c⁺ cells arose among the PECs with ingested OMLs. CD11c⁺ cells also developed among enriched peritoneal CD11b^highCD11⁻ cells from OML-treated mice, and the resulting CD11c⁺ cells expressed co-stimulatory molecules and MHC class II. In addition, OML-ingesting CD11b^highCD11c⁺ cells were found in spleen after the enriched peritoneal macrophages with ingested OMLs were transplanted in the peritoneal cavity of mice. These results show that a fraction of peritoneal macrophages can differentiate into mature DCs following uptake of OMLs.     

Role of T‐bet,the master regulator of Th1 cells,in the cytotoxicity of murine CD4+ T cells

Although CD4⁺ T cells are generally regarded as helper T cells, some activated CD4⁺ T cells have cytotoxic properties. Given that CD4⁺ cytotoxic T lymphocytes (CTLs) often secrete IFN‐γ, CTL activity among CD4⁺ T cells may be attributable to Th1 cells, where a T‐box family molecule, T‐bet serves as the “master regulator”. However, although the essential contribution of T‐bet to expression of IFN‐γ has been well‐documented, it remains unclear whether T‐bet is involved in CD4⁺ T cell‐mediated cytotoxicity. In this study, to investigate the ability of T‐bet to confer cytolytic activity on CD4⁺ T cells, the T‐bet gene (Tbx21) was introduced into non‐cytocidal CD4⁺ T cell lines and their cytolytic function analyzed. Up‐regulation of FasL (CD178), which provided the transfectant with cytotoxicity, was observed in Tbx21transfected CD4⁺ T cells but not in untransfected parental cells. In one cell line, T‐bet transduction also induced perforin gene (Prf1) expression and Tbx21 transfectants efficiently killed Fas^? target cells. Although T‐bet was found to repress up‐regulation of CD40L (CD154), which controls FasL‐mediated cytolysis, the extent of CD40L up‐regulation on in vitro‐differentiated Th1 cells was similar to that on Th2 cells, suggesting the existence of a compensatory mechanism. These results collectively indicate that T‐bet may be involved in the expression of genes, such as FasL and Prf1, which confer cytotoxicity on Th1 cells.

     

In Vivo T Cell Activation Induces the Formation of CD209+ PDL-2+ Dendritic Cells

Two critical functions of dendritic cells (DC) are to activate and functionally polarize T cells. Activated T cells can, in turn, influence DC maturation, although their effect on de novo DC development is poorly understood. Here we report that activation of T cells in mice, with either an anti-CD3 antibody or super antigen, drives the rapid formation of CD209⁺CD11b⁺CD11c⁺ MHC II⁺ DC from monocytic precursors (Mo-DC). GM-CSF is produced by T cells following activation, but surprisingly, it is not required for the formation of CD209⁺ Mo-DC. CD40L, however, is critical for the full induction of Mo-DC following T cell activation. T cell induced CD209⁺ Mo-DC are comparable to conventional CD209^- DC in their ability to stimulate T cell proliferation. However, in contrast to conventional CD209^- DC, CD209⁺ Mo-DC fail to effectively polarize T cells, as indicated by a paucity of T cell cytokine production. The inability of CD209⁺ Mo-DC to polarize T cells is partly explained by increased expression of PDL-2, since blockade of this molecule restores some polarizing capacity to the Mo-DC. These findings expand the range of signals capable of driving Mo-DC differentiation in vivo beyond exogenous microbial factors to include endogenous factors produced following T cell activation.     

Natural Killer Cell Receptor+ T‐Lymphocytes in Normal and Helicobacter pylori‐Infected Human Gastric Mucosa

Background: Helicobacter pylori infection is associated with development of chronic inflammation and infiltration of immune cells into the gastric mucosa. As unconventional T‐lymphocytes expressing natural killer cell receptors are considered to play central roles in the immune response against infection, a study investigating their frequencies in normal and H. pylori‐infected gastric mucosa was undertaken. Materials and Methods: Flow cytometry was used to quantify T‐cells expressing the natural killer cell markers CD161, CD56, and CD94 in freshly isolated lymphocytes from the epithelial and lamina propria layers of gastric mucosa. Thirteen H. pylori‐positive and 24 H. pylori‐negative individuals were studied. Results: CD94⁺ T‐cells were the most abundant (up to 40%) natural killer receptor‐positive T‐cell population in epithelial and lamina propria layers of H. pylori‐negative gastric mucosa. CD161⁺ T‐cells accounted for about one‐third of all T‐cells in both compartments, but the lowest proportion were of CD56⁺ T‐cells. Compared with H. pylori‐negative mucosa, in H. pylori‐infected mucosa the numbers of CD161⁺ T‐cells were significantly greater (p = .04) in the epithelium, whereas the numbers of CD56⁺ T‐cells were lower (p = .01) in the lamina propria. A minor population (< 2%) of T‐cells in both mucosal layers of H. pylori‐negative subjects were natural killer T‐cells, and whose proportions were not significantly different (p > .05) to those in H. pylori‐infected individuals. Conclusions: The predominance, heterogeneity, and distribution of natural killer cell receptor‐positive T‐cells at different locations within the gastric mucosa reflects a potential functional role during H. pylori infection and warrants further investigation.