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5 Cards in this Set
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immune surveillance
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a physiologic function of the adaptive immune system is to prevent the outgrowth of transformed cells or to destroy these cells before they become harmful tumors.
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The principal immune mechanism of tumor eradication
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The principal immune mechanism of tumor eradication is killing of tumor cells by CTLs specific for tumor antigens.
A majority of tumor antigens that elicit immune responses in tumor-bearing individuals are endogenously synthesized cytosolic proteins that are displayed as class I major histocompatibility complex (MHC)-associated peptides. Therefore, these antigens are recognized by class I MHC-restricted CD8+ CTLs, whose function is to kill cells producing the antigens. |
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Mechanisms tumors develop for evading immune responses
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Some tumors stop expressing the antigens that are the targets of immune attack. These tumors are called "antigen loss variants."
Other tumors stop expressing class I MHC molecules, so they cannot display antigens to CD8+ T cells. Other tumors may secrete cytokines, such as transforming growth factor-β, that suppress immune responses. Some tumors engage normal T cell inhibitory pathways, such as those mediated by CTLA-4 or PD-1, and thus suppress anti-tumor immune responses. |
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How could a NK cell eradicate a tumor trying to evade the immune system?
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Sometumors stop expressing class I MHC molecules in attempt to evade the immune system, so they cannot display antigens to CD8+ T cells.
NK cells recognize molecules expressed on tumor cells, but not on normal cells, and are activated when their target cells lack class I MHC molecules. Therefore, NK cells may provide a mechanism for killing class I MHC-negative tumors. |
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Main strategies for cancer/tumor immunotherapy
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The main strategies for cancer immunotherapy aim to provide antitumor effectors (antibodies and T cells) to patients, actively immunize patients against their tumors, and stimulate the patients' own antitumor immune responses.
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