We analyzed the interaction between human peripheral blood natural killer (NK) cells and monocyte-derived immature dendritic cells (DC). Fresh NK cells were activated, as indicated by the induced expression of the CD69 antigen, and their cytolytic activity was strongly augmented by contact with lipopolysaccharide (LPS)-treated mature DC, or with immature DC in the presence of the maturation stimuli LPS, Mycobacterium tuberculosis or interferon (IFN)-α. Reciprocally, fresh NK cells cultured with immature DC in the presence of the maturation stimuli strongly enhanced DC maturation and interleukin (IL)-12 production. IL-2–activated NK cells directly induced maturation of DC and enhanced their ability to stimulate allogeneic naive CD4+ T cells. The effects of NK cells were cell contact dependent, although the secretion of IFN-γ and TNF also contributed to DC maturation. Within peripheral blood lymphocytes the reciprocal activating interaction with DC was restricted to NK cells, because the other lymphocyte subsets were neither induced to express CD69, nor induced to mature in contact with DC. These data demonstrated for the first time a bidirectional cross talk between NK cells and DC, in which NK cells activated by IL-2 or by mature DC induce DC maturation.

We analyzed interleukin (IL) 12 and IL-23 production by monocyte-derived dendritic cells (mono-DCs). Mycobacterium tuberculosis H37Rv and zymosan preferentially induced IL-23. IL-23 but not IL-12 was efficiently induced by the combination of nucleotide-binding oligodimerization domain and Toll-like receptor (TLR) 2 ligands, which mimics activation by M. tuberculosis, or by the human dectin-1 ligand beta-glucan alone or in combination with TLR2 ligands, mimicking induction by zymosan. TLR2 ligands inhibited IL-12 and increased IL-23 production. DC priming with interferon (IFN) gamma strongly increased IL-12 production, but was not required for IL-23 production and inhibited IL-23 production induced by beta-glucan. The pattern of IL-12 and IL-23 induction was reflected in accumulation of the IL-12p35 and IL-23p19 transcripts, respectively, but not IL-12/23p40. Although IL-23, transforming growth factor beta, and IL-6 contained in the supernatants of activated mono-DCs played a role in the induction of IL-17 by human CD4(+) T cells, IL-1beta, in combination with one or more of those factors, was required for IL-17 production, and its production determined the differential ability of the stimuli used to elicit mono-DCs to produce soluble factors directing IL-17 production. Thus, the differential ability of pathogens to induce antigen-presenting cells to produce cytokines regulates the immune response to infection

Activation of metabotropic glutamate receptors (mGluRs) leads to modulation of a variety of second messenger pathways probably including the mitogen-activated protein kinase (MAPK) extracellular signal-regulated protein kinases (ERK). MAPK play a key role in the control of cellular responses to changes in the external environment by regulating transcriptional activity and the phosphorylation state of several cytoplasmic targets. In this study, Chinese hamster ovary (CHO) cells permanently transfected with rat mGluR1a, mGluR2 and mGluR4 were employed as a model to examine the activation of MAPK by glutamate through mGluRs. All three mGluR subtypes rapidly stimulated ERK activation. In particular, mGluR1a and mGluR2 preferentially mediated phosphorylation and activation of ERK2 in a pertussis toxin (PTX)-sensitive and concentration-dependent manner. The activation was blocked completely by pretreatment with the antagonist (rs)-alpha-methyl-4-carboxyphenylglycine (MCPG) or with the MEK inhibitor PD098059. Furthermore, mGluR1a-mediated ERK activation was suppressed by the depletion of endogenous protein kinase C (PKC) activity and by the PKC inhibitors staurosporine and calphostin C, but not chelerythrine. When cAMP was elevated in mGluR2-expressing cells, by forskolin or dibutyryl-cAMP, slight elevation of ERK activity was observed. However, glutamate-stimulated ERK activation remained unaffected. In these cells, the phosphatidylinositol 3 kinase (PI3K) inhibitor wortmannin produced a significant, albeit only partial, inhibition of mGluR2-mediated ERK activation. These findings raise the possibility of a MAPK cascade involvement in glutamate-dependent neuronal plasticity mediated through stimulation of mGluRs.

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A soluble recombinant form of Neisseria meningitidis adhesin A (NadAΔ351–405), proposed as a constituent of anti-meningococcal B vaccines, is here shown to specifically interact with and immune-modulate human monocyte-derived dendritic cells (mo-DCs). After priming with IFN-γ and stimulation with NadAΔ351–405, mo-DCs strongly up-regulated maturation markers CD83, CD86, CD80, and HLA-DR, secreted moderate quantities of TNF-α, IL-6, and IL-8, and produced a slight, although significant, amount of IL-12p70. Costimulation of mo-DCs with NadAΔ351–405 and the imidoazoquinoline drug R-848, believed to mimic bacterial RNA, increased CD86 in an additive way, but strongly synergized the secretion of IL-12p70, IL-1, IL-6, TNF-α, and MIP-1α, especially after IFN-γ priming. CD86/CD80 overexpression correlated with the occupation of high-(kd ∼ 80 nM) and low-(kd ∼ 4 μM) affinity binding sites for NadAΔ351–405. Alternatively, secretion of IL-12p70 and TNF-α, IL-6, and IL-8 corresponded to the occupation of high- or low-affinity receptors, respectively. Mo-DCs matured by IFN-γ and NadAΔ351–405 supported the proliferation of naive CD4+ T lymphocytes, inducing the differentiation of both IFN-γ and IL-4 producing phenotypes. Our data show that NadA not only is a good immunogen but is as well endowed with a proimmune, self-adjuvating, activity.