Which of the following produces the antibodies employed in the specific immune response of vertebrates?
Answer: A
Correct answer: B lymphocytes
Antibodies are made by B lymphocytes - strictly, by the plasma cells they become once activated. T lymphocytes carry the cell-mediated response and help B cells but secrete no antibody; neutrophils and macrophages phagocytose.
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Lack of reaction to our own human leukocyte antigens (HLAs) is known as?
Answer: D
Correct answer: tolerance
Tolerance is the trained unresponsiveness of the immune system to the body’s own molecules. It is established chiefly in the thymus and bone marrow, where lymphocytes reacting strongly to self antigens are deleted or silenced, and maintained afterwards by regulatory T cells. When it fails, the result is autoimmunity.
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An insect bite may result in inflammation of that spot. It is triggered by alarm chemicals such as
Answer: B
Correct answer: Histamine and kinins
The swelling and redness round a bite are produced by locally released mediators. Histamine comes from mast cell granules and dilates the small vessels while making them leaky; kinins, chiefly bradykinin, do the same and also stimulate the pain fibres, which is why the spot itches and hurts. Interferons act against viruses, opsonins tag microbes for phagocytosis, and histones are nuclear proteins.
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Interferons are
Answer: A
Correct answer: Cytokine barriers
Interferons are cytokines released by virus-infected cells; they make neighbouring cells resistant to infection and rouse natural killer cells. They belong to the cytokine barrier of innate immunity - chemical signals rather than physical structures or cells.
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Adaptive immune responses are more specific that innate immune responses.
Answer: A
Acquired (or adaptive) immune systems are more specific than the innate immune responses and can distinguish between two very similar molecules. The adaptive immune responses possess a memory i.e. an individual cannot develop the same disease twice.
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Which of the following provides specific defence against viruses and bacteria by producing antibodies?
Answer: B
Correct answer: B cells
Antibodies are made by B cells - strictly, by the plasma cells they mature into - and each antibody fits one particular antigen, which is what makes the defence specific. Complement and inflammation are innate and non-specific; T cells are specific too, but they act on infected cells rather than by secreting antibody.
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