8,050 research outputs found
Gamma interferon enhances internalization and early nonoxidative killing of Salmonella enterica serovar Typhimurium by human macrophages and modifies cytokine responses
No full textGamma interferon (IFN-gamma) is a critical cytokine in host defense against salmonella infections, but its role in phagocytic killing of intracellular Salmonella spp. has been investigated mainly in animal rather than human cells. We measured the effect of recombinant IFN-gamma (rIFN-gamma) priming on bacterial internalization, intracellular killing, oxidative burst, and cytokine release during phagocytosis of Salmonella enterica serovar Typhimurium by human monocyte-derived macrophages (MDM). Eleven-day-old MDM, primed for 72 h with rIFN-gamma (100 ng/ml) exhibited an increased proportion of cells with associated bacteria (31% versus 26%, P = 0.036) and a 67% increase in internalized bacteria per cell compared to unprimed cells (P = 0.025). Retrieval of viable bacteria following internalization was reduced 3.6-fold in 72-h primed versus unprimed MDM (interquartile range, 3.1 to 6.4) at 0.5 h due to enhanced early intracellular killing, and this difference was maintained up to 24 h. In contrast, cells primed for only 24 h exhibited no increase in early killing. MDM were competent to produce an early oxidative burst when stimulated with phorbol myristate acetate, which was fully abrogated by the respiratory burst inhibitor diphenyleneiodonium chloride (DPI), but infection of MDM with S. enterica serovar Typhimurium did not cause an increase in the early respiratory burst under unprimed or primed conditions, and DPI had no effect on the early killing of bacteria by primed or unprimed MDM. During 24 h following infection, rIFN-gamma-primed MDM released more interleukin-12 (IL-12) and less IL-10 relative to unprimed cells. We conclude that 72-h priming with rIFN-gamma increases the efficiency of internalization and nonoxidative early intracellular killing of S. enterica serovar Typhimurium by human macrophages and modifies subsequent cytokine release.</p
A cardinal role for cathepsin D in co-ordinating the host-mediated apoptosis of macrophages and killing of pneumococci
Get PDFThe bactericidal function of macrophages against pneumococci is enhanced by their apoptotic demise, which is controlled by the anti-apoptotic protein Mcl-1. Here, we show that lysosomal membrane permeabilization (LMP) and cytosolic translocation of activated cathepsin D occur prior to activation of a mitochondrial pathway of macrophage apoptosis. Pharmacological inhibition or knockout of cathepsin D during pneumococcal infection blocked macrophage apoptosis. As a result of cathepsin D activation, Mcl-1 interacted with its ubiquitin ligase Mule and expression declined. Inhibition of cathepsin D had no effect on early bacterial killing but inhibited the late phase of apoptosis-associated killing of pneumococci in vitro. Mice bearing a cathepsin D-/- hematopoietic system demonstrated reduced macrophage apoptosis in vivo, with decreased clearance of pneumococci and enhanced recruitment of neutrophils to control pulmonary infection. These findings establish an unexpected role for a cathepsin D-mediated lysosomal pathway of apoptosis in pulmonary host defense and underscore the importance of apoptosis-associated microbial killing to macrophage function
Immune-mediated phagocytosis and killing of Streptococcus pneumoniae are associated with direct and bystander macrophage apoptosis
No full textApoptosis of macrophages may be a pathogen-directed mechanism of immune escape or may represent appropriate host response to infection. Human monocyte-derived macrophages (MDMs) from healthy donors (C-MDMs) exhibited low-level constitutive apoptosis, but culture of MDMs with opsonized serotype I Streptococcus pneumoniae (I-MDMs) for 20 h resulted in significantly increased apoptosis. I-MDM apoptosis was associated with phagocytosis of bacteria and intracellular killing that was blocked by the caspase inhibitor z-VAD-fmk but not by Fas-blocking antibody. Paraformaldehyde-fixed I-MDMs induced apoptosis in uninfected syngeneic monocytes at levels greater than those in monocytes incubated alone or incubated with fixed C-MDMs. Apoptosis of syngeneic monocytes was blocked by anti-Fas antibody. The immune response of macrophages to S. pneumoniae includes a novel form of apoptosis that is associated with successful phagocytosis and bacterial killing. This response in vivo may regulate the inflammatory response to infection during a successful host response against S. pneumoniae
Analysis of histone post translational modifications in primary monocyte derived macrophages using reverse phase×reverse phase chromatography in conjunction with porous graphitic carbon stationary phase.
Get PDFA two dimensional-liquid chromatography (2D-LC) based approach was developed for the identification and quantification of histone post translational modifications in conjunction with mass spectrometry analysis. Using a bottom-up strategy, offline 2D-LC was developed using reverse phase chromatography. A porous graphitic carbon stationary phase in the first dimension and a C18 stationary phase in the second dimension interfaced with mass spectrometry was used to analyse global levels of histone post translational modifications in human primary monocyte-derived macrophages. The results demonstrated that 84 different histone peptide proteoforms, with modifications at 18 different sites including combinatorial marks were identified, representing an increase in the identification of histone peptides by 65% and 51% compared to two different 1D-LC approaches on the same mass spectrometer. The use of the porous graphitic stationary phase in the first dimension resulted in efficient separation of histone peptides across the gradient, with good resolution and is orthogonal to the online C18 reverse phase chromatography. Overall, more histone peptides were identified using the 2D-LC approach compared to conventional 1D-LC approaches. In addition, a bioinformatic pipeline was developed in-house to enable the high throughput efficient and accurate quantification of fractionated histone peptides. The automation of a section of the downstream analysis pipeline increased the throughput of the 2D-LC-MS/MS approach for the quantification of histone post translational modifications
Letter from David Babbitt to Ralph Cameron
No full textLetter from David Babbitt supporting the establishment of a post office in the Grand Canyon National Park
Monocytes regulate the mechanism of T-cell death by inducing Fas-mediated apoptosis during bacterial infection.
Get PDFMonocytes and T-cells are critical to the host response to acute bacterial infection but monocytes are primarily viewed as amplifying the inflammatory signal. The mechanisms of cell death regulating T-cell numbers at sites of infection are incompletely characterized. T-cell death in cultures of peripheral blood mononuclear cells (PBMC) showed 'classic' features of apoptosis following exposure to pneumococci. Conversely, purified CD3(+) T-cells cultured with pneumococci demonstrated necrosis with membrane permeabilization. The death of purified CD3(+) T-cells was not inhibited by necrostatin, but required the bacterial toxin pneumolysin. Apoptosis of CD3(+) T-cells in PBMC cultures required 'classical' CD14(+) monocytes, which enhanced T-cell activation. CD3(+) T-cell death was enhanced in HIV-seropositive individuals. Monocyte-mediated CD3(+) T-cell apoptotic death was Fas-dependent both in vitro and in vivo. In the early stages of the T-cell dependent host response to pneumococci reduced Fas ligand mediated T-cell apoptosis was associated with decreased bacterial clearance in the lung and increased bacteremia. In summary monocytes converted pathogen-associated necrosis into Fas-dependent apoptosis and regulated levels of activated T-cells at sites of acute bacterial infection. These changes were associated with enhanced bacterial clearance in the lung and reduced levels of invasive pneumococcal disease
Streptococcus pneumoniae-associated human macrophage apoptosis after bacterial internalization via complement and Fcgamma receptors correlates with intracellular bacterial load
No full textOpsonization enhances Streptococcus pneumoniae-induced human monocyte-derived macrophage (MDM) apoptosis. Both depletion of complement and immunoglobulin from opsonizing serum and blockade of the macrophages CR1, CR3, FcgammaRII, and FcgammaRIII partially decreased MDM apoptosis after S. pneumoniae phagocytosis, and these effects correlated with reduced numbers of internalized bacteria. Chloramphenicol inhibition of protein synthesis by opsonized S. pneumoniae down-regulated subsequent MDM apoptosis. Phagocytosis of an unencapsulated mutant of S. pneumoniae resulted in increased MDM apoptosis, in association with enhanced internalization. Caspase inhibition was associated with decreased killing of bacteria. Enhanced induction of apoptosis by opsonized S. pneumoniae is the result of increased intracellular burden of bacteria, rather than of a specific pattern of engagement of complement receptor or FcgammaR. A dynamic interaction between live intracellular bacteria and the host cell is necessary for induction of apoptosis in MDMs, and induction of apoptosis contributes to the host defense against S. pneumoniae
A defence of Mr. Garrick, in answer to the letter-writer. With remarks upon plays and players, and the present state of the stage. By a dramatic author [electronic resource].
No full textThe letter-writer = H. W., i.e. Edward Purdon, author of 'A letter to David Garrick, Esq; on opening the Theatre' published 13 October, 1759.Price from imprint: price One-Shilling.Electronic reproduction.English Short Title Catalog,Reproduction of original from British Library
Toll-like receptors in health and disease: complex questions remain
No full textUntil recently, the manner in which we respond to pathogens was obscure. It is now clear that a family of proteins, the Toll-like receptors (TLRs),3 contribute to the signal transduction induced by many pathogen-associated molecular patterns (PAMPs), and perhaps also to endogenous damage signals generated at sites of inflammation. Some TLRs act as central integrators of a wide variety of signals, responding to diverse agonists with an apparently common output, while other members of the family show (to date) considerable specificity with regard to their stimuli. However, many questions remain regarding the immunopharmacology of TLRs, their roles in innate immunity, and their manipulation by pathogens
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