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  • 1. Lindberg, Bo G
    et al.
    Merritt, Eleanor A
    Rayl, Melanie
    Liu, Chenxiao
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Parmryd, Ingela
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Olofsson, Berit
    Faye, Ingrid
    Immunogenic and Antioxidant Effects of a Pathogen-Associated Prenyl Pyrophosphate in Anopheles gambiae2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 8, p. e73868-Article in journal (Refereed)
    Abstract [en]

    Despite efficient vector transmission, Plasmodium parasites suffer great bottlenecks during their developmental stages within Anopheles mosquitoes. The outcome depends on a complex three-way interaction between host, parasite and gut bacteria. Although considerable progress has been made recently in deciphering Anopheles effector responses, little is currently known regarding the underlying microbial immune elicitors. An interesting candidate in this sense is the pathogen-derived prenyl pyrophosphate and designated phosphoantigen (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), found in Plasmodium and most eubacteria but not in higher eukaryotes. HMBPP is the most potent stimulant known of human Vγ9Vδ2 T cells, a unique lymphocyte subset that expands during several infections including malaria. In this study, we show that Vγ9Vδ2 T cells proliferate when stimulated with supernatants from intraerythrocytic stages of Plasmodium falciparum cultures, suggesting that biologically relevant doses of phosphoantigens are excreted by the parasite. Next, we used Anopheles gambiae to investigate the immune- and redox- stimulating effects of HMBPP. We demonstrate a potent activation in vitro of all but one of the signaling pathways earlier implicated in the human Vγ9Vδ2 T cell response, as p38, JNK and PI3K/Akt but not ERK were activated in the A. gambiae 4a3B cell line. Additionally, both HMBPP and the downstream endogenous metabolite isopentenyl pyrophosphate displayed antioxidant effects by promoting cellular tolerance to hydrogen peroxide challenge. When provided in the mosquito blood meal, HMBPP induced temporal changes in the expression of several immune genes. In contrast to meso-diaminopimelic acid containing peptidoglycan, HMBPP induced expression of dual oxidase and nitric oxide synthase, two key determinants of Plasmodium infection. Furthermore, temporal fluctuations in midgut bacterial numbers were observed. The multifaceted effects observed in this study indicates that HMBPP is an important elicitor in common for both Plasmodium and gut bacteria in the mosquito.

  • 2.
    Liu, Chenxiao
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Vγ9Vδ2 T cells - response to P. falciparum-derived phosphoantigens and potential for use in colon cancer immunotherapy 2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Vγ9Vδ2 T cell is the dominant circulating γδ T cell subset in humans, can expand massively upon malaria infection and are cytotoxic to cancer cells. Vγ9Vδ2 T cells are stimulated by phosphoantigens, primarily isoprenoid pyrophosphates like isopentenyl pyrophosphate and (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP). Vγ9Vδ2 T cell from human blood were studied for proliferation, response to blood-stage malaria parasites and during colon cancer progression. Vγ9Vδ2 T cell proliferation was stimulated by media from P. falciparum-infected erythrocytes from all asexual blood stages - rings, trophozoites, schizonts and rupturing schizonts as well as sexual stage gametocytes assessed by the protocols we developed to obtain pure cultures of all stages. Further, we demonstrated that the molecules that stimulated the Vγ9Vδ2 T cell proliferation are phosphoantigens that are released from intact infected erythrocytes. This does not require schizont rupture.  Interestingly, the parasites consumed all the iron ion of hemoglobins during their development from the ring to the rupturing schizont stage. We found that an Anopheles gambiae immune cell line responds to HMBPP by activation of MAPK and PI3K signaling pathways. Moreover, transcription of dual oxidase and nitric oxide synthase was upregulated by addition of HMBPP in the midgut of Anopheles gambiae which increases cell tolerance to oxidative stress. A range of small isoprenoid pyrophosphates were found to stimulate proliferation of Vγ9Vδ2 T cells from PBMCs as was the isoprenoid monophosphate DMAP. However other isoprenoid monophosphates and alcohols did not. We found that cryopreserved unexpectedly increase the proliferation ability of HMBPP–stimulated PBMCs. To test the cytotoxicity of Vγ9Vδ2 T cells against adherent colon cancer cell lines, a flow cytometry-based assay was developed. Using the assay we found that proliferated Vγ9Vδ2 T cells are cytotoxcitic to various cancer cells and that HMBPP increases cytotoxicity towards adherent colon cancer cells. In a clinical study we found that Vγ9Vδ2 T cells could not always be proliferated from colon cancer patients and that the inflammatory homing receptor CXCR3 was expressed at higher levels in colon cancer patients than the control group. Moreover, at cancer stadium 4 a lower frequency of Vγ9Vδ2 T cells was more common than in the other groups.

  • 3.
    Liu, Chenxiao
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Emami, S. Noushin
    Pettersson, Jean
    Ranford-Cartwright, Lisa
    Faye, Ingrid
    Parmryd, Ingela
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    V gamma 9V delta 2 T cells proliferate in response to phosphoantigens released from erythrocytes infected with asexual and gametocyte stage Plasmodium falciparum2018In: Cellular Immunology, ISSN 0008-8749, E-ISSN 1090-2163, Vol. 334, p. 11-19Article in journal (Refereed)
    Abstract [en]

    V gamma 9V delta 2 T cells, the dominant gamma delta T cell subset in human peripheral blood, are stimulated by phosphoantigens, of which (E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate, is produced in the apicoplast of malaria parasites. Cell-free media from synchronised Plasmodium falciparum asexual ring, trophozoite, and schizont stage-cultures of high purity as well as media from ruptured schizont cultures, all stimulated V gamma 9V delta 2 T cell proliferation, as did media from pure gametocyte cultures, whereas media from uninfected erythrocytes cultures did not. The media from ruptured schizont cultures and all the asexual and gametocyte stage cultures contained only background iron levels, suggesting that all erythrocyte haemoglobin is consumed as the parasites develop and supporting that the phosphoantigens were released from intact parasitized erythrocytes. The V gamma 9V delta 2 T cell-stimulating agent was not affected by freezing, thawing or heating but was sensitive to phosphatase treatment, confirming its phosphoantigen identity. In summary, phosphoantigens are released from parasitised erythrocytes at all developmental blood stages.

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