Induction of Salmonella stress proteins upon infection of macrophages
Article Abstract:
When a disease-producing agent (a pathogen) invades the body's cells, its survival depends on developing good strategies for fighting the body's defenses. One of the most hostile environments, from a pathogen's point of view, is the inside of the macrophage, a cell whose job it is to engulf and destroy cell debris. Salmonella typhimurium, however, is capable of growing in macrophages. In this setting, the organism synthesizes several proteins called macrophage-induced proteins (MIPs). Proteins synthesized by S. typhimurium under these circumstances were compared with the proteins manufactured by the bacteria when no macrophages were present. At least 12 MIPs seem to be synthesized only in macrophages, and are absent from S. typhimurium in other settings. Two proteins were heat shock proteins, molecules that are immunodominant antigens (provoke a strong immune response) in other infectious organisms. Normally, increased temperature is necessary for expression of these proteins, but they were manufactured in infected macrophages without this requirement. It is possible that proteins manufactured in large quantities in macrophages, such as heat shock proteins, acquire their immunodominance because they are presented on the cell's surface as part of the macrophage's antigen-presenting role (macrophages 'present' antigens, or foreign proteins, to other cells of the immune system so they can destroy them). This may be one way organisms like S. typhimurium acquire their virulence, and may explain why living attenuated vaccines, where the organisms can still manufacture small amounts of immune-stimulating substances, usually protect better than killed vaccines. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Science
Subject: Science and technology
ISSN: 0036-8075
Year: 1990
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T cells against a bacterial heat shock protein recognize stressed macrophages
Article Abstract:
Heat shock proteins are molecules that are produced by cells when they are exposed to various stress conditions such as heat, infection by viruses or activation by lymphokines, molecules released by lymphocytes, cells of the immune system. These proteins persist throughout the evolutionary scale and are similar in organisms as different as bacteria and humans. A protein similar to the heat shock protein produced by mycobacteria, which cause tuberculosis and leprosy, was identified in macrophages in mice. Macrophages are cells of the immune system that are involved in phagocytosis, the engulfment and destruction of infectious organisms such as bacteria. The protein is recognized by cytolytic T cells, also immune cells, which are involved in the destruction of virus- and bacteria-infected cells and tumor cells. Since the protein is similar in many organisms, these T cells can react with and destroy cells infected with a variety of organisms. Since the protein is present in macrophages under stressful conditions, the reactivity of cytotoxic T cells to this protein can also cause an autoimmune response, in which the immune system mounts an attack against the body's own cells and tissues, in this case to the immune system's own macrophages, which may result in autoimmune disease.
Publication Name: Science
Subject: Science and technology
ISSN: 0036-8075
Year: 1989
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Cells in stress: transcriptional activation of heat shock genes
Article Abstract:
Cells exposed to stress, such as high temperatures, go through a series of steps that ensure the survival of the cell. When exposed to heat shock, the stressed cell assembles into a trimer, engages in binding activity and becomes phospphorylated.
Publication Name: Science
Subject: Science and technology
ISSN: 0036-8075
Year: 1993
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