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Complement-mediated Lysis (complement-mediated + lysis)
Selected AbstractsDiagnosing PNH with FLAER and multiparameter flow cytometryCYTOMETRY, Issue 3 2007D. Robert Sutherland Abstract Background: PNH is an acquired hematopoietic stem cell disorder leading to a partial or absolute deficiency of all glycophosphatidyl-inositol (GPI)-linked proteins. The classical approach to diagnosis of PNH by cytometry involves the loss of at least two GPI-linked antigens on RBCs and neutrophils. While flow assays are more sensitive and specific than complement-mediated lysis or the Hams test, they suffer from several drawbacks. Bacterial aerolysin binds to the GPI moiety of cell surface GPI-linked molecules and causes lysis of normal but not GPI-deficient PNH cells. FLAER is an Alexa488-labeled inactive variant of aerolysin that does not cause lysis of cells. Our goals were to develop a FLAER-based assay to diagnose and monitor patients with PNH and to improve detection of minor populations of PNH clones in other hematologic disorders. Methods: In a single tube assay, we combined FLAER with CD45, CD33, and CD14 allowing the simultaneous analysis of FLAER and the GPI-linked CD14 structure on neutrophil and monocyte lineages. Results: Comparison to standard CD55 and CD59 analysis showed excellent agreement. Because of the higher signal to noise ratio, the method shows increased sensitivity in our hands over single (CD55 or CD59) parameter analysis. Using this assay, we were able to detect as few as 1% PNH monocytes and neutrophils in aplastic anemia, that were otherwise undetectable using CD55 and CD59 on RBC's. We also observed abnormal FLAER staining of blast populations in acute leukemia. In these cases, the neutrophils stained normally with FLAER, while the gated CD33bright cells failed to express normal levels of CD14 and additionally showed aberrant CD45 staining and bound lower levels of FLAER. Conclusion: FLAER combined with multiparameter flow cytometry offers an improved assay for diagnosis and monitoring of PNH clones and may have utility in detection of unsuspected myeloproliferative disorders. © 2007 Clinical Cytometry Society [source] Antibody-mediated bacterial clearance from the lower respiratory tract of mice requires complement component C3EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 1 2004Elizabeth Abstract To assess the contribution of complement to respiratory immunity in the context of a natural bacterial infection, we used mice genetically deficient in complement components and the murine pathogen Bordetella bronchiseptica. Complement component C3 was not required for the control of bacterial infection or for the generation of infection-induced protective immunity. However, C3-deficient (C3,/,) mice were severely defective, compared to wild type, in vaccine-induced protective immunity. Adoptively transferred immune serum from convalescent wild-type or C3,/, animals rapidly cleared B.,bronchiseptica from the lungs of wild-type mice but did not affect its growth in C3,/, mice, indicating that the defect is not in the generation of protective immunity, but in its function. Immune serum was effective in C5-deficient mice but had little effect in the lungs of mice lacking either Fc, receptors (Fc,R) or CR3, suggesting bacterial clearance is not via direct complement-mediated lysis. Together, these data indicate that complement is required for antibody-mediated clearance of Bordetella and suggest the mechanism involves C3 opsonization of bacteria for phagocytosis that is both CR3- and Fc,R-dependent. [source] Lyme borreliosis , an updateJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 5 2007Elisabeth Aberer Summary Lyme borreliosis is the most common tick-borne, infectious disease in the northern hemisphere. Disease manifestations in the United States and Europe vary as a result of geographic distribution of different species within the genospecies Borrelia burgdorferi sensu lato, which in turn are host-specific. Certain toxigenic B. burgdorferi strains cause early disseminated disease. The ability of Borrelial organisms to break down the extracellular matrix also promotes dissemination. B. burgdorferi are eliminated by complement-mediated lysis and by T and B cell activity of the specific immune response. Yet, B. burgdorferi can evade humoral immunity by means of type of protective mechanism by which it adheres to the proteoglycan decorin in the joints and skin. A further factor in the persistence of the pathogen is altered antigen expression. Re-infection usually occurs with a different strain, although repeated infection with the same strain is also possible after a certain period of latency. New developments in serologic testing include the use of recombinant native antigen as well as antigens produced in vivo such as VlsE (variable major protein-like sequence, expressed) or decorin-binding protein A. Diagnosis continues to be complicated by seropositivity of healthy individuals, the persistence of antibodies after therapy, and a lacking humoral immune response in patients with erythema migrans. [source] Modulation of proteins in Naegleria fowleri amebae by bacteriaTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005ANGELA E. FRITZINGER Naegleria fowleri are free-living amebae found in soil and freshwater habitats that cause a fatal disease in humans called Primary Amoebic Meningoencephalitis. In the natural environment, amebae feed on bacteria. In the infected host, the amebae lyse and ingest nerve tissue. Proteins that lyse and degrade bacteria and mammalian cells have been described and are termed as naegleriapores or pore-forming proteins (PFP). In order to prevent autolysis from PFPs, Naegleria may have developed mechanisms that enable the amebae to survive in the presence of cytolytic molecules. Recently, we have established that N. fowleri express a "CD59-like" surface protein, but the function of this protein in amebae has not been elucidated. In mammalian cells, CD59 is a complement,regulatory protein that inhibits complement-mediated lysis of cells expressing this protein. In the present study, expression of the "CD59-like" protein in response to bacteria and bacterial toxins was investigated. Co-culture of N. fowleri with log phase Escherichia coli or Pseudomonas aeruginosa resulted in differential expression of the "CD59-like" protein. Treatment of the amebae with bacterial toxin also affected expression of the protein. Scanning and transmission electron microscopy demonstrated morphological changes in N. fowleri following co-incubation with the bacteria. Under all conditions examined, the amebae remained intact and viable. The results of our study implicate a possible protective role of the "CD59-like" protein in response to bacterial predators and bacterial toxins. [source] How tumour necrosis factor blockers interfere with tuberculosis immunityCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 1 2010J. Harris Summary Tumour necrosis factor (TNF) is a potent inflammatory cytokine that plays an important role in immunity to numerous bacterial infections, including Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB) in humans. Infliximab, adalimumab, certolizumab pegol and etanercept are anti-TNF agents used to treat a range of inflammatory/autoimmune diseases, such as rheumatoid arthritis. The use of some of these drugs has been linked to reactivation TB. In addition to blocking TNF-mediated immune responses, some anti-TNF drugs have been found to interfere with innate immune responses, such as phagolysosomal maturation and monocyte apoptosis, as well as cell-mediated responses, including interferon-, secretion by memory T cells, complement-mediated lysis of Mtb-reactive CD8+ T cells and increased regulatory T cell activity. This review summarizes some of the reported effects of TNF blockers on immune cell responses in the context of the observed clinical data on TB reactivation in patients on anti-TNF therapy. [source] | |||||||||||||