Macrophages activated by the gram negative bacterial product lipopolysaccharide (LPS) switch their core metabolism from oxidative phosphorylation to glycolysis1. Inhibition of glycolysis with 2-deoxyglucose (2DG) suppressed LPS-induced Interleukin-1 beta (IL-1β) but not Tumour necrosis factor alpha (TNFα) in macrophages. A comprehensive metabolic map of LPS-activated macrophages revealed up-regulation of glycolytic and down-regulation of mitochondrial genes, which correlated directly with the expression profiles of altered metabolites. LPS strongly increased the TCA cycle intermediate succinate. Glutamine-dependent anerplerosis was the major source of succinate with the ‘Gamma-Aminobutyric Acid (GABA)-shunt’ pathway also playing a role. LPS-induced succinate stabilized Hypoxia-inducible factor 1α (HIF-1α), an effect inhibited by 2DG, with IL-1β as an important target. LPS also increases succinylation of several proteins. Succinate is therefore identified as a metabolite in innate immune signalling which leads to enhanced IL-1β production during inflammation.

NK cells are cytotoxic lymphocytes that also secrete regulatory cytokines and can therefore influence adaptive immune responses. NK cell function is largely controlled by genes present in a genomic region named the NK complex. It has been shown that the NK complex is a genetic determinant of murine cerebral malaria pathogenesis mediated by Plasmodium berghei ANKA. In this study, we show that NK cells are required for cerebral malaria disease induction and the control of parasitemia. NK cells were found infiltrating brains of cerebral malaria-affected mice. NK cell depletion resulted in inhibition of T cell recruitment to the brain of P. berghei-infected animals. NK cell-depleted mice displayed down-regulation of CXCR3 expression and a significant reduction of T cells migrating in response to IFN-γ-inducible protein 10, indicating that this chemokine pathway plays an essential role in leukocyte trafficking leading to cerebral disease and fatalities.

Plasmodium falciparum malaria causes 660 million clinical cases with over 2 million deaths each year. Acquired host immunity limits the clinical impact of malaria infection and provides protection against parasite replication. Experimental evidence indicates that cell-mediated immune responses also result in detrimental inflammation and contribute to severe disease induction. In both humans and mice, the spleen is a crucial organ involved in blood stage malaria clearance, while organ-specific disease appears to be associated with sequestration of parasitized erythrocytes in vascular beds and subsequent recruitment of inflammatory leukocytes. Using a rodent model of cerebral malaria, we have previously found that the majority of T lymphocytes in intravascular infiltrates of cerebral malaria-affected mice express the chemokine receptor CXCR3. Here we investigated the effect of IP-10 blockade in the development of experimental cerebral malaria and the induction of splenic anti-parasite immunity. We found that specific neutralization of IP-10 over the course of infection and genetic deletion of this chemokine in knockout mice reduces cerebral intravascular inflammation and is sufficient to protect P. berghei ANKA-infected mice from fatality. Furthermore, our results demonstrate that lack of IP-10 during infection significantly reduces peripheral parasitemia. The increased resistance to infection observed in the absence of IP-10-mediated cell trafficking was associated with retention and subsequent expansion of parasite-specific T cells in spleens of infected animals, which appears to be advantageous for the control of parasite burden. Thus, our results demonstrate that modulating homing of cellular immune responses to malaria is critical for reaching a balance between protective immunity and immunopathogenesis.

High, early IFN-gamma production by live parasite-stimulated peripheral blood mononuclear cells is a correlate of immunity to symptomatic malaria in Papua New Guinean children, and natural killer-like gammadelta T cells may contribute to protection.

IntroductionNatural killer (NK) cells are innate lymphocytes specialized in cytokine production and cytotoxicity toward tumors and virusinfected cells. NK cells develop in the bone marrow from hematopoietic stem cells (HSCs) via lymphoid precursors. 1 The earliest committed NK-cell precursors can be isolated from lineage marker-negative fetal thymus or adult bone marrow and express high levels of the interleukin 15 (IL-15)/interleukin 2 receptor␤ (IL-2R␤) chain (CD122 2 ). NK-cell precursors then undergo maturation and functional diversification in the bone marrow, thymus, and a variety of peripheral organs including the liver, spleen, and lymph nodes. 1 In the mouse, peripheral maturation in the spleen is characterized by the up-regulation of the markers CD43, Mac-1 (CD11b), CD94, and KLRG1, with concomitant down-regulation of CD27 and ckit. 1,[3][4][5][6] Mature Mac-1 high KLRG1 ϩ CD27 low NK cells are the dominant population in nonlymphoid organs (with the exception of the liver). 3,7 In contrast to B and T cells, knowledge about the transcriptional circuitries controlling NK-cell development and maturation remains limited. Several factors, including E4BP4, 8,9 Tox, 10 and Id2, 11 are required for the development of NK cells from early progenitors, whereas GATA3 is essential for thymic NK cells 12 and modulates the function of mature NK cells. 13 A second group of transcription factors, including Ets1, 14 E74-like factor 4, 15 interferon regulatory factor 2 (IRF2), 16 and T-bet, 17,18 is more specifically required for the later stages of NK-cell differentiation and function. Interestingly, a number of these factors, including Id2 and T-bet, also have important functions in CD8 ϩ T-cell differentiation. 19,20 Blimp1 (also known as Prdm1) is a pleiotropic transcription factor that plays crucial roles in the differentiation of plasma cells and CD8 ϩ effector T cells. [21][22][23][24][25] In both processes, Blimp1 is required for terminal differentiation and Blimp1 deficiency leads to loss of functional antibody-secreting cells and short-lived cytotoxic T cells. Moreover, in CD8 ϩ T cells, Blimp1 is required for the optimal expression of cytotoxic molecules such as granzyme B and perforin and for the regulation of chemokine receptors such as CC-chemokine receptor 7 (CCR7), CCR5, and CCR6, but is dispensable for most cytokine production. 24,25 Blimp1 is also broadly required for the maintenance of T-cell homeostasis, because mice that lack Blimp1 in all T cells or mice reconstituted with Blimp1-deficient fetal liver cells show an accumulation of activated T cells and develop immunopathology. 22,26 In CD4 ϩ T cells, Blimp1 has been suggested to attenuate Th1 differentiation by repressing the genes encoding T-bet and interferon␥ (IFN␥). 27 Blimp1 expression within B and T cells is controlled by 2 transcription factors, IRF4 and Bcl6. While Bcl6 and Blimp1 mutually repress the expression of each other in activated B and CD4 ϩ T cells, 28 IRF4 directly activates Blimp1 expression. 29 We show that Blimp1 is expressed ...

The infection of mice with Plasmodium berghei ANKA constitutes the best available mouse model for human Plasmodium falciparum-mediated cerebral malaria, a devastating neurological syndrome that kills nearly 2.5 million people every year. Experimental data suggest that cerebral disease results from the sequestration of parasitized erythrocytes within brain blood vessels, which is exacerbated by host proinflammatory responses mediated by cytokines and effector cells including T lymphocytes. Here, T cell responses to P. berghei ANKA were analyzed in cerebral malaria-resistant and -susceptible mouse strains. CD4؉ T-cell proliferation and interleukin-2 (IL-2) production in response to parasite-specific and polyclonal stimuli were strongly inhibited in cerebral malaria-resistant mice. In vitro and in vivo depletion of CD4 ؉ CD25 ؉ regulatory T (T reg ) cells significantly reversed the inhibition of CD4 ؉ T-cell proliferation and IL-2 production, indicating that this cell population contributes to the suppression of T-cell function during malaria. Moreover, in vivo depletion of T reg cells prevented the development of parasite-specific TH1 cells involved in the induction of cerebral malaria during a secondary parasitic challenge, demonstrating a regulatory role for this cell population in the control of pathogenic responses leading to fatal disease.

The role of early to intermediate Plasmodium falciparum-induced cellular responses in the development of clinical immunity to malaria is not well understood, and such responses have been proposed to contribute to both immunity and risk of clinical malaria episodes. To investigate whether P. falciparum-induced cellular responses are able to function as predictive correlates of parasitological and clinical outcomes, we conducted a prospective cohort study of children (5 to 14 years of age) residing in a region of Papua New Guinea where malaria is endemic Live, intact P. falciparum-infected red blood cells were applied to isolated peripheral blood mononuclear cells obtained at baseline. Cellular cytokine production, including production of interleukin-2 (IL-2), IL-4, IL-6, IL-10, tumor necrosis factor (TNF) (formerly tumor necrosis factor alpha), and gamma interferon (IFN-␥), was measured, and the cellular source of key cytokines was investigated. Multicytokine models revealed that increasing P. falciparum-induced IL-6 production was associated with an increased incidence of P. falciparum clinical episodes (incidence rate ratio [ Individuals living in regions of moderate to high malaria endemicity slowly acquire clinical immunity to Plasmodium falciparum throughout their lives in an age-and exposuredependent manner (3,29). This immunity enables them to control parasite replication at densities below that which induces clinical symptoms (29,46). Both antibody-dependent and T-cell-dependent acquired immune responses have been shown to play an important role in the development of clinical immunity (13,29). The role of early to intermediate cellular responses, however, is less well understood, and such responses have been proposed to contribute to both immunity and risk of clinical malaria episodes (45,49,51).Early cellular immune responses are rapidly initiated during malaria infection and are thought to play an important role both in limiting initial parasite replication and in directly shaping subsequent adaptive immune responses (45,49,51). However, the overproduction or inappropriate regulation of both proinflammatory cytokines, such as interleukin-1 (IL-1), IL-6, gamma interferon (IFN-␥), and tumor necrosis factor (TNF) (formerly tumor necrosis factor alpha), and anti-inflammatory cytokines, such as IL-10, IL-4, and transforming growth factor ␤ (TGF-␤), may also lead to localized and systemic inflammation and has been associated with symptomatic and severe malaria (7,45). The clinical outcome of an infection may thus depend on the appropriate induction and counterregulation of both pro-and anti-inflammatory cytokine secretion. Understanding how this network of P. falciparum-induced cellular responses is associated with immunity and risk of clinical disease in malaria exposed-children could provide important insights for the development of effective vaccines.Studies investigating the association between P. falciparumor antigen-induced secretion of cytokines from peripheral blood mononuclear cells (PBMCs) and prosp...

Loss of function of the tumor suppressor gene PRDM1 (also known as BLIMP1) or deregulated expression of the oncogene BCL6 occurs in a large proportion of diffuse large B cell lymphoma (DLBCL) cases. However, targeted mutation of either gene in mice leads to only slow and infrequent development of malignant lymphoma, and despite frequent mutation of BCL6 in activated B cells of healthy individuals, lymphoma development is rare. Here we show that T cells prevent the development of overt lymphoma in mice caused by Blimp1 deficiency or overexpression of Bcl6 in the B cell lineage. Impairment of T cell control results in rapid development of DLBCL-like disease, which can be eradicated by polyclonal CD8(+) T cells in a T cell receptor-, CD28- and Fas ligand-dependent manner. Thus, malignant transformation of mature B cells requires mutations that impair intrinsic differentiation processes and permit escape from T cell-mediated tumor surveillance.