Borrelia burgdorferi-pulsed dendritic cells induce a protective immune response against tick-transmitted spirochetes.

Borrelia burgdorferi-pulsed dendritic cells and epidermal cells were able to initiate the production of anti-outer surface protein A (OspA) antibody in vitro with normal T and B cells from either BALB/c or C3H/HeJ mice. Inhibition of anti-B. burgdorferi antibody production was observed after 3 days, but not after 2 days, of exposure of the antigen-presenting cells to tumor necrosis factor alpha +/- granulocyte-macrophage colony-stimulating factor. Furthermore, splenic dendritic cells pulsed in vitro with live B. burgdorferi spirochetes and then adoptively transferred into naive syngeneic mice mediated a protective immune response against tick-transmitted spirochetes. This protection appeared not to be due to killing of spirochetes in the feeding ticks, since ticks fed to repletion on B. burgdorferi-pulsed dendritic cell-sensitized mice still harbored live spirochetes. Western blot analysis of the sera collected from dendritic cell-sensitized mice demonstrated that the mice responded to a limited set of B. burgdorferi antigens, including OspA, -B, and -C compared to control groups that either had received unpulsed dendritic cells or were not treated. Finally, mice in the early stage of B. burgdorferi infection were able to develop anti-OspA antibody following injection with B. burgdorferi-pulsed dendritic cells. Our results demonstrate for the first time that adoptive transfer of B. burgdorferi-pulsed dendritic cells induces a protective immune response against tick-transmitted B. burgdorferi and stimulates the production of antibodies specific for a limited set of B. burgdorferi antigens in vivo.     

Natural killer dendritic cells are an intermediate of developing dendritic cells

NK dendritic cells (DCs; NKDCs) appear to emerge as a distinct DC subset in humans and rodents, which have the functions of NK cells and DCs. However, the developmental relationship of NKDCs (CD11c(+)NK1.1(+)) to CD11c(+)NK1.1(-) DCs has not been addressed. Herein, we show that NKDCs exist exclusively in the compartment of CD11c(+)MHC II(-) cells in the steady state and express variable levels of DC subset markers, such as the IFN-producing killer DC marker B220, in a tissue-dependent manner. They can differentiate into NK1.1(-) DCs, which is accompanied by the up-regulation of MHC Class II molecules and down-regulation of NK1.1 upon adoptive transfer. However, NK cells (NK(+)CD11c(-)) did not differentiate into NK1.1(+)CD11c(+) cells upon adoptive transfer. Bone marrow-derived Ly6C(+) monocytes can be a potential progenitor of NKDCs, as some of them can differentiate into CD11c(+)NK1.1(+) as well as CD11c(+)NK1.1(-) cells in vivo. The steady-state NKDCs have a great capacity to lyse tumor cells but little capability to present antigens. Our studies suggest that NKDCs are an intermediate of developing DCs. These cells appear to bear the unique surface phenotype of CD11c(+)NK1.1(+)MHC II(-) and possess strong cytotoxic function yet show a poor ability to present antigen in the steady state. These findings suggest that NKDCs may play a critical role in linking innate and adaptive immunity.     

Dendritic cells in the initiation of immune responses against central nervous system-derived antigens

Antigen presentation is essential for the activation and maintenance of antigen-specific T cell responses in the nervous tissue. Generally, it is becoming well accepted that the antigen presenting cell (APC) type responsible for the initiation of the primary immune response through the exclusive ability to activate na?ve T cells is the dendritic cell (DC); however, the role of these cells in central nervous system (CNS) immunity is unclear at this time. The diverse phenotypes and origins of DCs make the characterization of their function in the CNS even more difficult. It is believed that DCs can influence the immune response in several ways: these cells are not only capable of initiating the immune response but they are also a major determinant of peripheral tolerance. DCs are characterized by the constitutive ability to express MHC class II molecules as well as high-level upregulation of these molecules in response to inflammatory stimuli. A pan DC marker that has proved to be useful in identifying them is CD11c (the alpha-chain of CR4); other markers include CD205 and MHC class II. DCs also actively participate in the humoral immune response. In this review, we would like to discuss how DCs appear in the CNS and their roles in initiation, maintenance and tolerance in the immune reactions in the CNS.     

Enhanced secretion of interferon-gamma by bovine gammadelta T cells induced by coculture with Mycobacterium bovis-infected dendritic cells: evidence for reciprocal activating signals

Evidence suggests that gammadelta T cells form part of the innate immune response to Mycobacterium bovis infection. Dendritic cells (DCs) are capable of secreting high levels of interleukin-12 (IL-12) following infection with mycobacteria and can induce interferon-gamma (IFN-gamma) secretion by natural killer and gammadelta T cells We investigated the innate interactions occurring between WC1(+)gammadelta T cells and M. bovis-infected DCs. Following coculture with M. bovis-infected DCs, secretion of IFN-gamma and expression of CD25 and major histocompatibility complex class II on WC1(+)gammadelta T cells were significantly enhanced. Reciprocal enhancement of IL-12 secretion by the DCs was also observed and this interaction was found to be contact dependent. We hypothesize that there is an early, transient signal between the WC1(+)gammadelta T cells and the DCs, which promotes the synthesis of biologically active IL-12, and which is dependent upon cell-cell contact. Reciprocal signals including IL-12 are then delivered to WC1(+)gammadelta cells, which leads to the enhanced secretion of IFN-gamma, and the up-regulation of activation markers and antigen presentation molecules by the WC1(+)gammadelta T cells. These interactions are likely to form a critical part of the T helper type 1-conditioning response of DCs to M. bovis.     

Differential expression of alternative H2-M isoforms in B cells, dendritic cells and macrophages by proinflammatory cytokines

Major histocompatibility (MHC) class II heterodimers bind peptides generated by degradation of endocytosed antigens and display them on the surface of antigen presenting cells (APCs) for recognition by CD4+ T cells. Efficient loading of MHC class II molecules with peptides is catalyzed by the MHC class II-like molecule H2-M. The coordinate regulation of MHC class II and H2-M expression is a prerequisite for efficient MHC class II/peptide assembly in APCs determining both the generation of the T cell repertoire in the thymus and cellular immune responses in the periphery. Here we show that expression of H2-M and MHC class II genes is coordinately and cell type-specific regulated in splenic B cells, splenic dendritic cells (DCs) and peritoneal macrophages (Mphi) in response to proinflammatory and immunoregulatory cytokines, including GM-CSF, IFN-gamma, TGF-beta2, IL-4, IL-10 and viral IL-10. In addition, ratio-RT-PCR expression analysis of the duplicated H2-Mbeta-chain loci demonstrates for the first time that Mbl and Mb2 genes are differentially expressed in individual APC types. Mb2 is preferentially expressed in IL-4, GM-CSF, IL-10, vIL-10 and IFN-gamma stimulated splenic B cells, whereas splenic DCs express both Mb genes at almost equal levels. In contrast, peritoneal Mphi express predominantly Mb2 but stimulation with IFN-gamma induces a switch towards Mb1 expression. These data suggest a common mechanism that regulates coordinate expression of H2-M and MHC class II genes in professional APCs. Differential expression of Mb1 and Mb2, and by consequence alternative H2-M isoforms (Malphabeta1 or Malphabeta2), may influence the nature of the peptide repertoire presented by different APC types.     

Mycobacterium tuberculosis diverts alpha interferon-induced monocyte differentiation from dendritic cells into immunoprivileged macrophage-like host cells

Dendritic cells (DCs) are critical for initiating a pathogen-specific T-cell response. During chronic infections the pool of tissue DCs must be renewed by recruitment of both circulating DC progenitors and in loco differentiating monocytes. However, the interaction of monocytes with pathogens could affect their differentiation. Mycobacterium tuberculosis has been shown to variably interfere with the generation and function of antigen-presenting cells (APCs). In this study we found that when alpha interferon (IFN-alpha) is used as an inductor of monocyte differentiation, M. tuberculosis inhibits the generation of DCs, forcing the generation of immunoprivileged macrophage-like cells instead. Cells derived from M. tuberculosis-infected monocyte-derived macrophages (M. tuberculosis-infected MoMphi) retained CD14 without acquiring CD1 molecules and partially expressed B7.2 but did not up-regulate B7.1 and major histocompatibility complex (MHC) class I and II molecules. They synthesized tumor necrosis factor alpha and interleukin-10 (IL-10) but not IL-12. They also showed a reduced ability to induce proliferation and functional polarization of allogeneic T lymphocytes. Thus, in the presence of IFN-alpha, M. tuberculosis may hamper the renewal of potent APCs, such as DCs, generating a safe habitat for intracellular growth. M. tuberculosis-infected MoMphi, in fact, showed reduced expression of both signal 1 (CD1, MHC classes I and II) and signal 2 (B7.1 and B7.2), which are essential for mycobacterium-specific T-lymphocyte priming and/or activation. These data further suggest that M. tuberculosis has the ability to specifically interfere with monocyte differentiation. This ability may represent an effective M. tuberculosis strategy for eluding immune surveillance and persisting in the host.     

Dendritomas formed by fusion of mature dendritic cells with allogenic human hepatocellular carcinoma cells activate autologous cytotoxic T lymphocytes

Mature dendritic cells (DCs) have highly expressed CD1a, MHC class I, MHC class II, B7-1, B7-2 and ICAM-I molecules, all of which are essential for activation of na?ve T cells. In this study, dendritomas were formed by fusion of hepatocellular carcinoma (HCC) SMMC-7721 cells with autologous DCs in vitro. DCs were obtained from adherent monocytes cultured in the presence of GM-CSF and IL-4 and were matured in monocyte-conditioned media. Expression of MHC class II and HCC-specific antigen by these dendritomas were determined using a specific murine anti-HCC monoclonal antibody (mAb) specific for HCC cell line SMMC-7721, and a murine anti-human HLA-DR mAb, and was also confirmed using bi-dimensional flow cytometry and immuno-histostaining. Dendritomas were co-cultured with autologous T cells, resulting in activation of T cell proliferation and priming of na?ve T cells to induce MHC class I restricted lysis of HCC SMMC-7721 cells. The results imply that these dendritomas may have potential for use in HCC immunotherapy.     

Tolerogenic microenvironment in neonatal period induced by maternal immunization with ovalbumin

Maternal immunization with allergens, such as ovalbumin (OVA), can inhibit the development of an allergic response in offspring. The regulatory mechanisms seem to be mediated by maternal antibodies (MatAbs) and factors generated by the maternal–fetal interface. The aim of this study was to verify the pathways of inhibitory Ab transference after maternal immunization with OVA and the effect of the offspring's dendritic cells (DCs) on the generation of regulatory T (Treg) cells. We verified that preconceptional OVA immunization induces high levels of proinflammatory and regulatory cytokines in the amniotic fluid, allowing the transference of high levels of anti-OVA IgG1 Abs to the offspring. Using an adoptive nursing protocol, we verified that maternal immunization leads to MatAb transference by the placental route and by breastfeeding contribute to the inhibition of anaphylactic IgE and IgG1 Ab responses in immunized offspring. We observed that maternal immunization decreased eosinophil numbers in recovered bronchoalveolar lavage fluid and in the lung tissue, whereas with a lack of control of airway responsiveness to methacholine. Maternal immunization induced in young offspring a decreased percentage of CD11c+ DCs expressing MHC class II and CD40 molecules. Moreover, DCs from both groups of offspring when pulsed with OVA, were able to induce Treg cells in vitro. Similarly, OVA immunization at the neonatal stage increased the frequency of Treg cells, regardless of the mother's immunization status. These findings emphasize that maternal immunization leads to a complex interaction of regulatory factors, with MatAbs, DCs and Treg cells affecting the tolerance of offspring during an allergic response.     

In vitro generation of cytotoxic and regulatory T cells by fusions of human dendritic cells and hepatocellular carcinoma cells

Background

Human hepatocellular carcinoma (HCC) cells express WT1 and/or carcinoembryonic antigen (CEA) as potential targets for the induction of antitumor immunity. In this study, generation of cytotoxic T lymphocytes (CTL) and regulatory T cells (Treg) by fusions of dendritic cells (DCs) and HCC cells was examined.

Methods

HCC cells were fused to DCs either from healthy donors or the HCC patient and investigated whether supernatants derived from the HCC cell culture (HCCsp) influenced on the function of DCs/HCC fusion cells (FCs) and generation of CTL and Treg.

Results

FCs coexpressed the HCC cells-derived WT1 and CEA antigens and DCs-derived MHC class II and costimulatory molecules. In addition, FCs were effective in activating CD4⁺ and CD8⁺ T cells able to produce IFN-γ and inducing cytolysis of autologous tumor or semiallogeneic targets by a MHC class I-restricted mechanism. However, HCCsp induced functional impairment of DCs as demonstrated by the down-regulation of MHC class I and II, CD80, CD86, and CD83 molecules. Moreover, the HCCsp-exposed DCs failed to undergo full maturation upon stimulation with the Toll-like receptor 4 agonist penicillin-inactivated Streptococcus pyogenes. Interestingly, fusions of immature DCs generated in the presence of HCCsp and allogeneic HCC cells promoted the generation of CD4⁺ CD25^high Foxp3⁺ Treg and inhibited CTL induction in the presence of HCCsp. Importantly, up-regulation of MHC class II, CD80, and CD83 on DCs was observed in the patient with advanced HCC after vaccination with autologous FCs. In addition, the FCs induced WT1- and CEA-specific CTL that were able to produce high levels of IFN-γ.

Conclusion

The current study is one of the first demonstrating the induction of antigen-specific CTL and the generation of Treg by fusions of DCs and HCC cells. The local tumor-related factors may favor the generation of Treg through the inhibition of DCs maturation; however, fusion cell vaccination results in recovery of the DCs function and induction of antigen-specific CTL responses in vitro. The present study may shed new light about the mechanisms responsible for the generation of CTL and Treg by FCs.     

Activation of murine dendritic cells and macrophages induced by Salmonella enterica serovar Typhimurium

Macrophages and dendritic cells (DCs) are antigen-presenting cells (APCs), and the direct involvement of both cell types in the immune response to Salmonella has been identified. In this study we analysed the phenotypic and functional changes that take place in murine macrophages and DCs in response to live and heat-killed Salmonella enterica serovar Typhimurium. Both types of cell secreted proinflammatory cytokines and nitric oxide (NO) in response to live and heat-killed salmonellae. Bacterial stimulation also resulted in up-regulation of costimulatory molecules on macrophages and DCs. The expression of major histocompatibility complex (MHC) class II molecules by macrophages and DCs was differentially regulated by interferon (IFN)-gamma and salmonellae. Live and heat-killed salmonellae as well as lipopolysaccharide (LPS) inhibited the up-regulation of MHC class II expression induced by IFN-gamma on macrophages but not on DCs. Macrophages as well as DCs presented Salmonella-derived antigen to CD4 T cells, although DCs were much more efficient than macrophages at stimulating CD4 T-cell cytokine release. Macrophages are effective in the uptake and killing of bacteria whilst DCs specialize in antigen presentation. This study showed that the viability of salmonellae was not essential for activation of APCs but, unlike live bacteria, prolonged contact with heat-killed bacteria was necessary to obtain maximal expression of the activation markers studied.     

Immunohistochemical study of the local immune response in lambs experimentally infected with <Emphasis Type="Italic">Dicrocoelium dendriticum</Emphasis> (Digenea)

Phenotypic expression of inflammatory cells in liver and hepatic lymph nodes (HLN) has been examined in lambs experimentally infected with Dicrocoelium dendriticum using immunohistochemical techniques. Thirty-two lambs, 12 infected with 1,000 D. dendriticum metacercariae, 12 with 3,000, and 8 controls were used. Half the lambs in each group were slaughtered on days 60 and 180 post-infection (p.i.), respectively. Primary antibodies (Abs) against T cell epitopes (CD3+, CD4+, CD8+ and WC1+ gammadelta), B cell epitopes (CD79alphacy+, CD45R+), immunoglobulin (IgG)-bearing plasma cells, macrophages (CD14+, VPM32+) and major histocompatibility complex (MHC) class IIbeta antigen were used. T lymphocytes (CD3+, CD4+ and CD8+) and B lymphocytes (CD79alphacy+ and CD45R+) with diffuse pattern or forming lymphoid aggregates and follicles surrounded the septal bile ducts (SBD) and inter-lobular bile ducts, whereas the WC1 gammadelta T cells were scattered. Numerous IgG+ plasma cells were observed around SBD. CD14 and VPM32+ macrophages intermingled with lymphocytes were immunostained by the anti-MHC class IIbeta. This Ab also reacted with lymphoid cells. Likewise, increased positive immunostaining for all Abs used was observed in the HLN of infected lambs. There was no qualitative difference regarding the phenotype expression of inflammatory cells between the lambs infected with D. dendriticum. The humoral and cell-mediated local immune responses observed were similar in the two groups of lambs infected with different doses.     

Therapy of established tumour with a hybrid cellular vaccine generated by using granulocyte–macrophage colony-stimulating factor genetically modified dendritic cells

Dendritic cells (DCs) are the most powerful of all antigen-presenting cells and play a critical role in the induction of primary immune responses. DC-based vaccination represents a potentially powerful strategy for cancer immunotherapy. In this study, a new approach for a DC-based melanoma vaccine was described. Splenic DCs from C57BL/6 mice were fused with B16 melanoma cells, and the resultant B16/DC hybrid cells expressed major histocompatibility complex (MHC) molecules - B7 as well as the B16 tumour marker M562 - which were enriched by Ia-mediated positive selection with a MiniMACS column. The fusion rates were 12.7-26.8%. To generate hybrid tumour vaccines with potentially greater potent therapeutic efficacy, we genetically engineered DCs with granulocyte-macrophage colony-stimulating factor (GM-CSF) prior to cell fusion. Recombinant adenovirus vector was used to mediate gene transfer into DCs with high efficiency and DCs expressed GM-CSF at 96-138 ng/105 cells/ml 24 hr after GM-CSF gene transfer. GM-CSF gene-modified DCs (DC.GM) exhibited higher expression of B7 and co-stimulatory capacity in mixed lymphocyte reaction (MLR). Fusion of DC.GM with B16 cells generated B16/DC.GM hybrid cells secreting GM-CSF at 59-63 ng/105 cells/ml. Immunization of C57BL/6 mice with the B16/DC hybrid vaccine elicited a specific cytotoxic T-lymphocyte (CTL) response and protected the immunized mice from B16 tumour challenge, reduced pulmonary metastases and extended the survival of B16 tumour-bearing mice. The B16/DC.GM hybrid vaccine was able to induce a CTL response and protective immunity more potently and tended to be therapeutically more efficacious than the B16/DC vaccine. In vivo depletion of T-cell subsets demonstrated that both CD8+ and CD4+ T cells were essential for the therapeutic effects of B16/DC and B16/DC.GM hybrid vaccines. Additionally, other non-specific effector cells may also contribute to tumour rejection induced by the B16/DC.GM hybrid vaccine. These data indicate that a DC-based hybrid tumour vaccine may be an attractive strategy for cancer immunotherapy, and that GM-CSF gene-modified DCs may lead to the generation of hybrid vaccines with potentially increased therapeutic efficacy.     

T-cell-independent responses to Borrelia burgdorferi are critical for protective immunity and resolution of lyme disease

The humoral immune response to Borrelia burgdorferi during persistent infection is critical to both protective and disease-resolving immunity. This study examined the role of B cells in the absence of T cells during these events, using mice with selected immune dysfunctions. At 6 weeks postinfection, an interval at which arthritis resolves in immunocompetent mice, arthritis severity was equivalent among immunocompetent mice, alphabeta(+)-T-cell-deficient mice, and mice lacking both alphabeta(+) and gammadelta(+) T cells. Arthritis severity was worse in SCID mice, which lack T and B lymphocytes. Carditis regressed in immunocompetent mice and those lacking both alphabeta(+) and gammadelta(+) T cells but remained active in mice lacking only alphabeta(+) T cells and in SCID mice. Mice lacking only alphabeta(+) T cells and those lacking both alphabeta(+) and gammadelta(+) T cells generated immunoglobulin M (IgM) and IgG3 B. burgdorferi-reactive antibodies. Sera from infected immunocompetent mice, mice lacking only alphabeta(+) T cells, and mice lacking both alphabeta(+) and gammadelta(+) T cells passively protected naive mice against challenge inoculation with B. burgdorferi. However, only sera from infected immunocompetent mice, but not sera from infected T-cell-deficient mice, were able to resolve arthritis when passively transferred to actively infected SCID mice. These data demonstrate that B-cell activation during a T-cell-independent response may be critical for resolution of arthritis and carditis and that protective antibodies are generated during this response.     

Composition of MHC class II-enriched lipid microdomains is modified during maturation of primary dendritic cells

Dendritic cells (DCs) are the most potent antigen presenting cells. Major histocompatibility complex (MHC) class II molecule expression changes with maturation; immature DCs concentrate MHC class II molecules intracellularly, whereas maturation increases surface expression of MHC class II and costimulatory molecules to optimize antigen presentation. Signal transduction via MHC class II molecules localized in lipid microdomains has been described in B lymphocytes and in the THP-1 monocyte cell line. We have characterized MHC class II molecules throughout human DC maturation with particular attention to their localization in lipid-rich microdomains. Only immature DCs expressed empty MHC class II molecules, and maturation increased the level of peptide-bound heterodimers. Ligand binding to surface human leukocyte antigen (HLA)-DR induced rapid internalization in immature DCs. The proportion of cell-surface detergent-insoluble glycosphingolipid-enriched microdomain-clustered HLA-DR was higher in immature DCs despite the higher surface expression of HLA-DR in mature DCs. Constituents of HLA-DR containing microdomains included the src kinase Lyn and the cytoskeletal protein tubulin in immature DCs. Maturation modified the composition of the HLA-DR-containing microdomains to include protein kinase C (PKC)-delta, Lyn, and the cytoskeletal protein actin, accompanied by the loss of tubulin. Signaling via HLA-DR redistributed HLA-DR and -DM and PKC-delta as well as enriching the actin content of mature DC microdomains. The increased expression of HLA-DR as a result of DC maturation was therefore accompanied by modification of the spatial organization of HLA-DR. Such regulation could contribute to the distinct responses induced by ligand binding to MHC class II molecules in immature versus mature DCs.     

Immunization with antigen-pulsed dendritic cells significantly improves the immune response to weak self-antigens

Dendritic cells (DCs) are the only professional antigen-presenting cells endowed with the ability to stimulate naïve T cells and initiate a primary immune response. For this reason, DC-based immunization has been shown to be highly effective in eliciting CTL responses to viruses and tumor-associated antigens. Here we report on the use of DC immunization to enhance the B cell-mediated humoral immune response to highly conserved proteins and the application of this approach to the generation of monoclonal antibodies (mAbs) against these proteins. To illustrate the technique we describe the production of mAbs to class II transactivator (CIITA), the major histocompatibility complex (MHC) CIITA, a difficult immunogen owing to its high degree of identity among species. We show that mice immunized with a combination of an intravenous injection of DCs pulsed with recombinant fragments of CIITA followed by intraperitoneal injection of the antigen in incomplete Freund's adjuvant induced a detectable antibody response against CIITA, while sera from mice immunized using the traditional method (i.e. intraperitoneal immunization with 50 μg of protein in complete Freund's adjuvant) gave an almost undetectable response. Furthermore, a total of four fusion experiments demonstrate that immunization with Ag-pulsed DCs is necessary for the efficient generation of hybridomas and a good yield of mAbs specific for the recombinant and the native endogenous CIITA protein. Conversely, four independent fusions carried out with splenocytes from mice immunized using the traditional method failed to produce anti-CIITA hybridomas. We propose that immunization with antigen-loaded DCs should be the method of preference when attempting to raise mAbs against weak self-immunogens.     

Immune responses against Abeta1-42 in HLA class II transgenic mice: implications for Abeta1-42 immune-mediated therapies

We have investigated whether polymorphic differences in the major histocompatibility complex (MHC) class II molecules influence humoral and cellular immune responses against Abeta1-42. To analyze the effects of mouse MHC class II and tolerance effects of overexpression of human APP in mice, we immunized Tg2576 and non-transgenic littermates bred into two different MHC backgrounds with Abeta1-42 and compared both B and T cell responses. We found that in the presence of the mouse C57BL/6 background, both B and T cell responses against Abeta1-42 were significantly suppressed. To directly test the contribution of human MHC class II, we immunized various human HLA class II transgenic (TG) mice with Abeta1-42 and analyzed anti-Abeta immune responses. HLA-DR3 and HLA-DQ8 TG mice generated modest B and T cell responses against Abeta1-42. The presence of HLA-DR3/DQ8 in double TG mice enhanced the overall immune response against Abeta1-42. In contrast, HLA-DR4 TG mice mounted strong T cell responses but failed to generate high titer antibody responses against Abeta1-42, whereas, the HLA-DQ6 TG mice were not able to mount significant B or T cell responses against Abeta1-42. These studies in mice suggest that the presence of certain MHC class II molecules or combinations of class II molecules can potentially influence the overall immune response against Abeta1-42.     

NK cell activation by KIR-binding antibody 1-7F9 and response to HIV-infected autologous cells in viremic and controller HIV-infected patients

Natural killer (NK) cells may be protective in HIV infection and are inhibited by killer cell immunoglobulin-like receptors (KIRs) interacting with MHC class I molecules, including HLA-C. Retention of HLA-C despite downregulation of other MHC class I molecules on HIV infected cells might protect infected cells from NK cell recognition in vitro. To assess the role of inhibitory HLA-C ligands in the capacity of NK cells to recognize autologous infected T cells, we measured NK cell degranulation in vitro in viremic patients, controllers with low viremia, and healthy donors. No difference in NK cell response to uninfected compared to HIV-1_IIIB infected targets was observed. Activation of NK cells was regulated by KIRs, because NK cell degranulation was increased by 1-7F9, a human antibody that binds KIR2DL1/L2/L3 and KIR2DS1/S2, and this effect was most pronounced in KIR haplotype B individuals.     

Natural killer cells activated by MHC class I(low) targets prime dendritic cells to induce protective CD8 T cell responses

Conserved molecular patterns derived from pathogenic microorganisms prime antigen-presenting dendritic cells (DC) to induce adaptive T cell responses. In contrast, virus-infected or tumor cells that express low levels of major histocompatibility complex (MHC) class I activate natural killer (NK) cells for direct killing. It is unknown whether NK cell recognition of MHC class I(low) targets can also induce adaptive T cell responses. Here, we show that MHC class I(low) targets initiate a cascade of immune responses, starting with the immediate activation of NK cells. The activated NK cells then prime DC to produce IL-12 and to induce highly protective CD8 T cell memory responses. Therefore, sensing of MHC class I(low) targets by NK cells can link innate and adaptive immunity to induce protective T cell responses and may alarm the immune system during early infection with noncytopathic viruses.     

Glycogen synthetase kinase 3 inhibition drives MIC-A/B to promote cytokine production by human natural killer cells in Dengue virus type 2 infection

Dengue virus (DENV) is the most widespread arbovirus worldwide and is responsible for major outbreaks. The host's immune response plays a crucial role in controlling this infection but might also contribute to the promotion of viral spread and immunopathology. In response to DENV infection, NK cells preferentially produce cytokines and are cytotoxic in the presence of specific antibodies. Here, we identified that DENV-2 inhibits glycogen synthase kinase 3 (GSK-3) activity to subsequently induce MHC class-1-related chain (MIC) A and MIC-B expression and IL-12 production in monocyte-derived DCs, independently of the STAT-3 pathway. The inhibition of GSK-3 by DENV-2 or small molecules induced MIC-A/B expression on monocyte-derived DCs, resulting in autologous NK cells of a specific increase in IFN-γ and TNF-α production, in the absence of direct cytotoxicity. Together, these findings identified GSK-3 as a regulator of MIC-A/B expression and suggested its role in DENV-2 infection to specifically induce cytokine production by NK cells.