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  • 1
    ISSN: 1432-1440
    Keywords: Key words Leishmania major ; Interleukin-4 knockout mice ; Cytokine ; T helper cell ; Macrophage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The study of experimental infection of inbred strains of mice with the intracellular protozoan parasite Leishmania major has contributed significantly not only to our understanding of this fascinating host/parasite relationship but also to that of many basic immunological phenomena. Much has been learned about the cognate interaction of antigen-specific T cells and antigen-presenting cells, about cytokine and T cell subset regulation, and the requirements for costimulation. Specifically, the immune response to experimental L. major infection is the paradigm for polarized T helper cell (Th) 1 and Th2 differentiation. In this model system a Th1 response characterized by interleukin (IL)-2 and interferon (IFN)-γ secretion leads to self-curing disease, whereas a Th2 response (IL-4, IL-10) leads to nonhealing disease. Numerous manipulations, including the injection of cytokines and of neutralizing anti-cytokine antibodies, cytokine transgene expression, and more recently cytokine and cytokine receptor gene knockout studies, have all provided intriguing new pieces to the still incomplete mosaic of our understanding of the immune response. Some of these findings were clearly unexpected and are still incompletely understood. For instance, based on earlier neutralizing anti-IL-4 monoclonal antibody injection studies, IL-4 gene-disrupted BALB/c mice were expected to be unable to mount the biased Th2 response typical of the IL-4+/+ wild-type mice and to be able to control their lesions; quite unexpectedly, the BALB/c IL-4 knockout mice remain unable to heal their L. major infection. Based on these unexpected findings, we reexamine the literature in an attempt to resolve this apparent paradox and to relate the large body of experimental findings in the mouse system to that which is known about natural and experimental infections in the human.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1831
    Keywords: Key words Cutaneous leishmaniasis ; Lipopolysaccharide responder ; Lipopolysaccharide nonresponder ; Cytokine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The course of cutaneous leishmaniasis was examined in mice from two genetically closely related strains, C57BL/10ScCr (Cr) and C57BL/10ScSn (Sn). Sn mice are able to heal Leishmania major infections, while Cr mice are unable to heal. The cutaneous lesions of the Cr mice progressed continuously and the increase in lesion size was paralleled by an unrestricted growth of the parasites in vivo. Cr mice, in contrast to their Sn counterparts, are highly resistant to all effects of lipopolysaccharide (LPS). The nonhealing L. major infection in Cr mice is in sharp contrast to the course of infection in another endotoxin-nonresponder mouse strain, C3H/HeJ, which heal infections with L. major. Cr mice exhibit, in addition to the defective LPS responsiveness, an impaired interferon-γ (IFN-γ) response after infection with a variety of microorganisms. The insufficient activation of parasitized macrophages to kill intracellular L. major could be due to the inability of splenocytes from infected Cr mice to secrete IFN-γ upon restimulation with L. major. IFN-γ is essential for the efficient activation of parasitized macrophages to kill intracellular L. major by producing nitric oxide (NO). Although bone marrow-derived Cr macrophages do not produce NO in response to LPS, both Sn and Cr macrophages release NO upon stimulation with IFN-γ and tumor necrosis factor, indicating that they are responsive to activation by these cytokines.
    Type of Medium: Electronic Resource
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