Papers by Annemieke ten Bokum
Infection and Immunity, 2008
Human macrophages infected with Mycobacterium tuberculosis may undergo apoptosis. Macrophage apop... more Human macrophages infected with Mycobacterium tuberculosis may undergo apoptosis. Macrophage apoptosis contributes to the innate immune response against M. tuberculosis by containing and limiting the growth of mycobacteria and also by depriving the bacillus of its niche cell. Apoptosis of infected macrophages is well documented; however, bystander apoptosis of uninfected macrophages has not been described in the setting of M. tuberculosis. We observed that uninfected human macrophages underwent significant bystander apoptosis 48 and 96 h after they came into contact with macrophages infected with avirulent M. tuberculosis. The bystander apoptosis was significantly greater than the background apoptosis observed in uninfected control cells cultured for the same length of time. There was no evidence of the involvement of tumor necrosis factor alpha, Fas, tumor necrosis factor-related apoptosis-inducing ligand, transforming growth factor , Toll-like receptor 2, or MyD88 in contact-mediated bystander apoptosis. This newly described phenomenon may further limit the spread of M. tuberculosis by eliminating the niche cells on which the bacillus relies.
Frontiers in Immunology, 2019
Lipid metabolism plays a key role in many cellular processes. We show here that regulatory T cell... more Lipid metabolism plays a key role in many cellular processes. We show here that regulatory T cells have enhanced lipid storage within subcellular lipid droplets (LD). They also express elevated amounts of both isoforms of diacylglycerol acyl transferase (DGAT1 & 2), enzymes required for the terminal step of triacylglycerol synthesis. In regulatory T-cells (Tregs), the conversion of diacylglycerols to triacylglycerols serves two additional purposes other than lipid storage. First, we demonstrate that it protects T cells from the toxic effects of saturated long chain fatty acids. Second, we show that Triglyceride formation is essential for limiting activation of protein kinase C via free diacyl glycerol moieties. Inhibition of DGAT1 resulted in elevated active PKC and nuclear NFKB, as well as impaired Foxp3 induction in response to TGFβ. Thus, Tregs utilize a positive feedback mechanism to promote sustained expression of Foxp3 associated with control of LD formation.
JCI insight, Jan 9, 2017
Tregs can adopt a catabolic metabolic program with increased capacity for fatty acid oxidation-fu... more Tregs can adopt a catabolic metabolic program with increased capacity for fatty acid oxidation-fueled oxidative phosphorylation (OXPHOS). It is unclear why this form of metabolism is favored in Tregs and, more specifically, whether this program represents an adaptation to the environment and developmental cues or is "hardwired" by Foxp3. Here we show, using metabolic analysis and an unbiased mass spectroscopy-based proteomics approach, that Foxp3 is both necessary and sufficient to program Treg-increased respiratory capacity and Tregs' increased ability to utilize fatty acids to fuel oxidative phosphorylation. Foxp3 drives upregulation of components of all the electron transport complexes, increasing their activity and ATP generation by oxidative phosphorylation. Increased fatty acid β-oxidation also results in selective protection of Foxp3(+) cells from fatty acid-induced cell death. This observation may provide novel targets for modulating Treg function or selection ...
In both cells and animals, cannibalism can transfer harmful substances from the consumed to the c... more In both cells and animals, cannibalism can transfer harmful substances from the consumed to the consumer. Macrophages are immune cells that consume their own dead via a process called cannibalistic efferocytosis. Macrophages that contain harmful substances are found at sites of chronic inflammation, yet the role of cannibalism in this context remains unexplored. Here we take mathematical and experimental approaches to study the relationship between cannibalistic efferocytosis and substance accumulation in macrophages. Through mathematical modelling, we deduce that substances which transfer between individuals through cannibalism will concentrate inside the population via a coalescence process. This prediction was confirmed for macrophage populations inside a closed system. We used image analysis of whole slide photomicrographs to measure both latex microbead and neutral lipid accumulation inside murine bone marrow-derived macrophages (104 – 105 cells) following their stimulation int...
Frontiers in immunology, 2017
The differentiation and effector functions of both the innate and adaptive immune system are inex... more The differentiation and effector functions of both the innate and adaptive immune system are inextricably linked to cellular metabolism. The features of metabolism which affect both arms of the immune system include metabolic substrate availability, expression of enzymes, transport proteins, and transcription factors which control catabolism of these substrates, and the ability to perform anabolic metabolism. The control of lipid metabolism is central to the appropriate differentiation and functions of T lymphocytes, and ultimately to the maintenance of immune tolerance. This review will focus on the role of fatty acid (FA) metabolism in T cell differentiation, effector function, and survival. FAs are important sources of cellular energy, stored as triglycerides. They are also used as precursors to produce complex lipids such as cholesterol and membrane phospholipids. FA residues also become incorporated into hormones and signaling moieties. FAs signal nuclear receptors and their ch...
8th Congress of the EUGMS / European Geriatric Medicine 3S (2012) S1-S32 glucometers and educatio... more 8th Congress of the EUGMS / European Geriatric Medicine 3S (2012) S1-S32 glucometers and education of staff are essential measures to reduce hospital admissions for care home residents with hypoglycaemia. Disclosure.-No significant relationships. http://dx.
Tuberculosis, 2014
AraC Transcriptional regulator Mycobacteria Mycobacterial two-hybrid system nat operon Proteinepr... more AraC Transcriptional regulator Mycobacteria Mycobacterial two-hybrid system nat operon Proteineprotein interaction s u m m a r y MSMEG_0307 is annotated as a transcriptional regulator belonging to the AraC protein family and is located adjacent to the arylamine N-acetyltransferase (nat) gene in Mycobacterium smegmatis, in a gene cluster, conserved in most environmental mycobacterial species. In order to elucidate the function of the AraC protein from the nat operon in M. smegmatis, two conserved palindromic DNA motifs were identified using bioinformatics and tested for protein binding using electrophoretic mobility shift assays with a recombinant form of the AraC protein. We identified the formation of a DNA:AraC protein complex with one of the motifs as well as the presence of this motif in 20 loci across the whole genome of M. smegmatis, supporting the existence of an AraC controlled regulon. To characterise the effects of AraC in the regulation of the nat operon genes, as well as to gain further insight into its function, we generated a DaraC mutant strain where the araC gene was replaced by a hygromycin resistance marker. The level of expression of the nat and MSMEG_0308 genes was down-regulated in the DaraC strain when compared to the wild type strain indicating an activator effect of the AraC protein on the expression of the nat operon genes.
Current Topics in Medicinal Chemistry, 2013
Vaccines are powerful public health tools that have been of tremendous benefit in protecting vuln... more Vaccines are powerful public health tools that have been of tremendous benefit in protecting vulnerable populations worldwide from many pathogens. However, vaccine-preventable diseases still remain a considerable burden and this is particularly true among aging and aged populations in industrialized countries. The predicted demographic shift in the population landscape towards an ever-increasing aging population and the evidence suggesting that older individuals mount less-than optimal immune response to vaccination have raised the question of improving vaccine responses in older individuals. This review presents recent progress in the understanding at the cellular and molecular levels of age related immune decline and strategies to translate current knowledge into the development of immunization strategies to promote healthy aging, keeping older members of our society autonomous and independent.
Methods Enzymol, 2009
Antibodies to mycolic acid antigens can be detected as surrogate markers of active tuberculosis (... more Antibodies to mycolic acid antigens can be detected as surrogate markers of active tuberculosis (TB) with evanescent field biosensors where the lipid antigens are encapsulated in liposomes. Standard immunoassay such as ELISA, where the lipid antigen is not encapsulated, but directly adsorbed to the well-bottoms of microtiter plates, does not yield the required sensitivity and specificity for accurate diagnosis of TB. One reason for this is the cross-reactivity of natural anti-cholesterol antibodies with mycolic acids. Mycolic acids (MA) are the major cell wall lipids of mycobacteria. Mycobacterial MA has immunomodulatory properties and elicits specific antibodies in tuberculosis patients. Liposomes were optimized for their use as carriers both for the presentation of immobilized purified mycobacterial MA on sensor surfaces, and as a soluble inhibitor of antibody binding in inhibition assays. By using an inhibition assay in the biosensor, the interference by anti-cholesterol antibodies is reduced. Here we describe the MA carrying capacity of liposomes with and without cholesterol as stabilizing agent, optimised concentration and size of liposomes for use in the biosensor assay, comparison of the methods for wave-guide and surface plasmon resonance biosensors and how the cholesteroid nature of MA can be demonstrated by biosensor when Amphotericin B is allowed to bind to MA in liposomes.
Molecular …, Jan 1, 2007
The Mycobacterium tuberculosis TetR-type regulator Rv3574 has been implicated in pathogenesis as ... more The Mycobacterium tuberculosis TetR-type regulator Rv3574 has been implicated in pathogenesis as it is induced in vivo, and genome-wide essentiality studies show it is required for infection. As the gene is highly conserved in the mycobacteria, we deleted the Rv3574 orthologue in Mycobacterium smegmatis (MSMEG_6042) and used real-time quantitative polymerase chain reaction and microarray analyses to show that it represses the transcription both of itself and of a large number of genes involved in lipid metabolism. We identified a conserved motif within its own promoter (TnnAACnnGTTnnA) and showed that it binds as a dimer to 29 bp probes containing the motif. We found 16 and 31 other instances of the motif in intergenic regions of M. tuberculosis and M. smegmatis respectively. Combining the results of the microarray studies with the motif analyses, we predict that Rv3574 directly controls the expression of 83 genes in M. smegmatis, and 74 in M. tuberculosis. Many of these genes are known to be induced by growth on cholesterol in rhodococci, and palmitate in M. tuberculosis. We conclude that this regulator, designated elsewhere as kstR, controls the expression of genes used for utilizing diverse lipids as energy sources, possibly imported through the mce4 system.
Chemistry and physics …, Jan 1, 2008
Methods in …, Jan 1, 2009
Infection and …, Jan 1, 2008
Human macrophages infected with Mycobacterium tuberculosis may undergo apoptosis. Macrophage apop... more Human macrophages infected with Mycobacterium tuberculosis may undergo apoptosis. Macrophage apoptosis contributes to the innate immune response against M. tuberculosis by containing and limiting the growth of mycobacteria and also by depriving the bacillus of its niche cell. Apoptosis of infected macrophages is well documented; however, bystander apoptosis of uninfected macrophages has not been described in the setting of M. tuberculosis. We observed that uninfected human macrophages underwent significant bystander apoptosis 48 and 96 h after they came into contact with macrophages infected with avirulent M. tuberculosis. The bystander apoptosis was significantly greater than the background apoptosis observed in uninfected control cells cultured for the same length of time. There was no evidence of the involvement of tumor necrosis factor alpha, Fas, tumor necrosis factor-related apoptosis-inducing ligand, transforming growth factor β, Toll-like receptor 2, or MyD88 in contact-mediated bystander apoptosis. This newly described phenomenon may further limit the spread of M. tuberculosis by eliminating the niche cells on which the bacillus relies.
Journal of …, Jan 1, 1999
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Papers by Annemieke ten Bokum