Joost H. N. Schuitemaker

Microbial Compounds Selectively Induce Th1 Cell-Promoting or Th2 Cell-Promoting Dendritic Cells In Vitro with Diverse Th Cell-Polarizing Signals

Upon microbial infection, specific Th1 or Th2 responses develop depending on the type of microbe. Here, we demonstrate that different microbial compounds polarize the maturation of human myeloid dendritic cells (DCs) into stably committed Th1 cell-promoting (DC1) or Th2 cell-promoting (DC2) effector DCs that polarize Th cells via different mechanisms. Protein extract derived from the helminth Schistosoma mansoni induced the development of DC2s that promote the development of Th2 cells via the enhanced expression of OX40 ligand. Likewise, toxin from the extracellular bacterium Vibrio cholerae induced development of DC2s as well, however, via an OX40 ligand-independent, still unknown mechanism. In contrast, toxin from the intracellular bacterium Bordetella pertussis induced the development of DC1s with enhanced IL-12 production, which promotes a Th1 cell development. Poly(I:C) (dsRNA, mimic for virus) induced the development of extremely potent Th1-inducing DC1, surprisingly, without an enhanced IL-12 production. The obtained DC1s and DC2s are genuine effector cells that stably express Th cell-polarizing factors and are unresponsive to further modulation. The data suggest that the molecular basis of Th1/Th2 polarization via DCs is unexpectedly diverse and is adapted to the nature of the microbial compounds.

IL-4 Is a Mediator of IL-12p70 Induction by Human Th2 Cells: Reversal of Polarized Th2 Phenotype by Dendritic Cells

IL-12 is a key inducer of Th1-associated inflammatory responses, protective against intracellular infections and cancer, but also involved in autoimmune tissue destruction. We report that human Th2 cells interacting with monocyte-derived dendritic cells (DC) effectively induce bioactive IL-12p70 and revert to Th0/Th1 phenotype. In contrast, the interaction with B cells preserves polarized Th2 phenotype. The induction of IL-12p70 in Th2 cell-DC cocultures is prevented by IL-4-neutralizing mAb, indicating that IL-4 acts as a Th2 cell-specific cofactor of IL-12p70 induction. Like IFN-γ, IL-4 strongly enhances the production of bioactive IL-12p70 heterodimer in CD40 ligand-stimulated DC and macrophages and synergizes with IFN-γ at low concentrations of both cytokines. However, in contrast to IFN-γ, IL-4 inhibits the CD40 ligand-induced production of inactive IL-12p40 and the production of either form of IL-12 induced by LPS, which may explain the view of IL-4 as an IL-12 inhibitor. The presently described ability of IL-4 to act as a cofactor of Th cell-mediated IL-12p70 induction may allow Th2 cells to support cell-mediated immunity in chronic inflammatory states, including cancer, autoimmunity, and atopic dermatitis.

Differential transmission of human immunodeficiency virus type 1 by distinct subsets of effector dendritic cells

ABSTRACT Dendritic cells (DC) support human immunodeficiency virus type 1 (HIV-1) transmission by capture of the virus particle in the mucosa and subsequent transport to the draining lymph node, where HIV-1 is presented to CD4+ Th cells. Virus transmission involves a high-affinity interaction between the DC-specific surface molecule DC-SIGN and the viral envelope glycoprotein gp120 and subsequent internalization of the virus, which remains infectious. The mechanism of viral transmission from DC to T cells is currently unknown. Sentinel immature DC (iDC) develop into Th1-promoting effector DC1 or Th2-promoting DC2, depending on the activation signals. We studied the ability of these effector DC subsets to support HIV-1 transmission in vitro. Compared with iDC, virus transmission is greatly upregulated for the DC1 subset, whereas DC2 cells are inactive. Increased transmission by DC1 correlates with increased expression of ICAM-1, and blocking studies confirm that ICAM-1 expression on DC is important for HIV transmission. The ICAM-1-LFA-1 interaction is known to be important for immunological cross talk between DC and T cells, and our results indicate that this cell-cell contact is exploited by HIV-1 for efficient transmission.

Intercellular Adhesion Molecule-1/LFA-1 Ligation Favors Human Th1 Development

Th cell polarization toward Th1 or Th2 cells is strongly driven by exogenous cytokines, in particular IL-12 or IL-4, if present during activation by Ag-presenting dendritic cells (DC). However, additional Th cell polarizing mechanisms are induced by the ligation of cell surface molecules on DC and naive Th cells. In the present study, the role of LFA-1/ICAM-1 ligation in human Th cell polarization was investigated. Triggering of LFA-1 on anti-CD3/CD28 stimulated naive Th cells with immobilized Fc-ICAM-1, in the absence of DC and exogenous cytokines, induced a marked shift toward Th1 cell development, accompanied by a dose-dependent decrease in GATA-3 expression and a dose-dependent increase in T-bet expression. Th1 polarization by LFA-1 ligation could be demonstrated only under low cytokine conditions, as it was largely overruled by IL-12 or IL-4. This IL-12-independent Th1-driving mechanism appears to be operated by certain subsets of effector DC. Maturation of DC by poly(I:C), a synthetic dsRNA, used as an in vitro model for viral infections, leads to the generation of Th1-driving effector DC (DC1), which express elevated levels of ICAM-1 but produce only low levels of IL-12p70. Blocking the ICAM-1/LFA-1 interaction in cocultures of these DC with naive Th cells attenuated their Th1-driving capacity. The molecular mechanism by which LFA-1 signaling supports Th1 differentiation is blocked by specific inhibitors of extracellular signal-regulated kinase phosphorylation. The present data indicate the existence of an IL-12-independent, extracellular signal-regulated kinase-mediated mechanism, through which high ICAM-1-expressing DC1 can drive Th1 polarization. This mechanism may be operational during viral infections.

Triggering of Innate Immune Responses by Schistosome Egg Glycolipids and Their Carbohydrate Epitope GalNAcβ1-4(Fucα1-2Fucα1-3)GlcNAc

To investigate the interactions of glycoconjugates with the innate immune system, peripheral blood mononuclear cells were stimulated with glycolipids derived from Schistosoma mansoni eggs and worms and with biochemically synthesized neoglycoconjugates. Egg glycolipids stimulated the production of interleukin (IL)--10, IL-6, and tumor necrosis factor--alpha in monocytes, whereas worm glycolipids failed to do so. When monoclonal antibodies that specifically recognize defined carbohydrate epitopes were used, the binding of a GalNAc beta 1-4(Fuc alpha 1-2Fuc alpha 1-3)GlcNAc (LDN-DF) reactive antibody was pronounced on egg glycolipids but was absent on worm glycolipids. The binding of antibodies that recognize Gal beta 1-4(Fuc alpha 1-3)GlcNAc (LewisX), GalNAc beta 1-4GlcNAc (LDN), and GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc (LDN-F) was comparable for both preparations. Cytokine production in response to neoglycoconjugates containing enzymatically synthesized glycans also was measured. The LDN-DF neoglycoconjugate was the most potent cytokine inducer, which indicates that this difucosylated glycan can act at the host-parasite interface and can trigger innate immune responses.

Differential susceptibility of naïve, central memory and effector memory T cells to dendritic cell-mediated HIV-1 transmission

BackgroundDendritic cells (DC) have been proposed to facilitate sexual transmission of HIV-1 by capture of the virus in the mucosa and subsequent transmission to CD4+ T cells. Several T cell subsets can be identified in humans: naïve T cells (TN) that initiate an immune response to new antigens, and memory T cells that respond to previously encountered pathogens. The memory T cell pool comprises central memory (TCM) and effector memory cells (TEM), which are characterized by distinct homing and effector functions. The TEM cell subset, which can be further divided into effector Th1 and Th2 cells, has been shown to be the prime target for viral replication after HIV-1 infection, and is abundantly present in mucosal tissues.ResultsWe determined the susceptibility of TN, TCM and TEM cells to DC-mediated HIV-1 transmission and found that co-receptor expression on the respective T cell subsets is a decisive factor for transmission. Accordingly, CCR5-using (R5) HIV-1 was most efficiently transmitted to TEM cells, and CXCR4-using (X4) HIV-1 was preferentially transmitted to TN cells.ConclusionThe highly efficient R5 transfer to TEM cells suggests that mucosal T cells are an important target for DC-mediated transmission. This may contribute to the initial burst of virus replication that is observed in these cells. TN cells, which are the prime target for DC-mediated X4 virus transmission in our study, are considered to inefficiently support HIV-1 replication. Our results thus indicate that DC may play a decisive role in the susceptibility of TN cells to X4 tropic HIV-1.

Analysis of Anthrax and Plague Biowarfare Vaccine Interactions with Human Monocyte-Derived Dendritic Cells

The anti-biowarfare anthrax and plague vaccines require repeated dosing to achieve adequate protection. To test the hypothesis that this limited immunogenicity results from the nature of vaccine interactions with the host innate immune system, we investigated molecular and cellular interactions between vaccines, dendritic cells (DCs), and T cells and explored the potential for adjuvants (pertussis) to boost induction of host immunity. Human monocyte-derived DCs were matured in the presence of vaccines and analyzed for their ability to induce Th1/Th2 development from naive T cells, expression of cell surface maturation/costimulation molecules, and cytokine production. The vaccines showed different behavior patterns. Although the plague vaccine is equivalent to control maturation factors in maturation and stimulation of DCs and induces strong MLR and Th outgrowth, the anthrax vaccine is a poor inducer of DC maturation, as indicated by low levels of HLA-DR, CD86, and CD83 induction and minimal proinflammatory cytokine production. Interestingly, however, anthrax vaccine-treated DCs stimulate Th1 and Th2 outgrowth and a limited MLR response. There was no sustained negative modulatory effects of the anthrax vaccine on DCs, and its limited stimulatory effects could be overridden by coculture with pertussis. These results were supported by analysis of anthrax vaccine recall responses in subjects vaccinated using pertussis as an adjuvant, who demonstrate anthrax-specific effector T cell responses. These data show that the anthrax vaccine is a suboptimal DC stimulus that may in part explain the observation that it requires repeated administration in vivo and offer a rational basis for the use of complementary DC-maturing adjuvants in combined immunotherapy.