Which of the following protects our body against disease-causing pathogens?
Answer: B
Correct answer: Immune system
The immune system is what defends against pathogens - barriers, phagocytes, complement, and the lymphocytes and antibodies of the acquired response. The respiratory, digestive and excretory systems serve gas exchange, nutrition and waste removal respectively.
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Which of the following systems protects our body against disease-causing microbes?
Answer: A
Correct answer: Immune system
The immune system is the body’s defence against pathogens: barriers such as skin and mucus keep most out, and the cells and antibodies of the blood and lymph deal with what gets in. The digestive, excretory and respiratory systems have their own jobs - though each carries immune defences of its own, such as gastric acid and the mucus-and-cilia escalator of the airways.
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Which of the following statements is true about Passive Immunity?
Answer: D
Correct answer: All of the above.
All three are true of passive immunity, and they follow from one fact: the antibodies are given, not made. Protection is therefore immediate, since no response has to be mounted; it is short-lived, weeks to months, because the antibodies are gradually broken down and nothing replaces them; and it can provoke reactions, since antiserum raised in another species is itself foreign protein.
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AIDS is caused by
Answer: A
Correct answer: RNA virus
HIV is a retrovirus: its genome is RNA, which reverse transcriptase copies into DNA that is then integrated into the host chromosome. It infects CD4 helper T cells, and their gradual loss is what leaves the patient open to the opportunistic infections that define AIDS.
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Skin, body hair, cilia, eyelashes, the respiratory tract and the gastrointestinal tract are examples of ________.
Answer: A
Correct answer: Physical barrier
These are all physical (anatomical) barriers: they block or sweep away invaders mechanically. Skin is a tough keratinised sheet, hair and eyelashes catch particles, cilia in the airways drive trapped material upwards, and the linings of the gut and respiratory tract present a continuous covered surface. They are the first line of defence and belong to innate immunity.
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A person is injected with gammaglobulin against hepatitis B. It is
Answer: A
Correct answer: Artificially acquired passive immunity
Gammaglobulin is a preparation of ready-made antibodies, so the recipient’s own immune system is bypassed entirely: the immunity is passive, and because it was injected rather than received across a placenta it is artificially acquired. It works at once, which is why it is used after a suspected exposure, but it fades within weeks and leaves no memory.
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Humoral immunity is mediated by ______________
Answer: C
Correct answer: lymphocytes
Humoral immunity depends on antibodies, and antibodies are made by B lymphocytes after they mature into plasma cells - with helper T lymphocytes, also lymphocytes, providing the signals that permit it. Mast cells and neutrophils belong to inflammation and phagocytosis; leucocyte is the general word for a white cell, of which lymphocytes are one kind.
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Which of the following is not involved in eliciting an immune response?
Answer: C
Correct answer: Brain
The brain is not a lymphoid organ; indeed it is immunologically privileged, shielded by the blood-brain barrier and patrolled by its own resident microglia rather than by circulating lymphocytes. The thymus is where T cells mature, and the spleen and lymph nodes are where antigen and lymphocytes are brought together for a response to begin.
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Which of the following cells is involved in cell-mediated immunity?
Answer: A
Correct answer: T-cells
Cell-mediated immunity is carried by T lymphocytes: cytotoxic T cells kill infected or cancerous cells directly, and helper T cells direct the rest of the response. B cells work through the antibodies they secrete, which is the humoral arm.
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A molecule that produces an immune response is
Answer: A
Correct answer: Antigen
An antigen is any molecule the immune system recognises as foreign and responds to - typically a protein or polysaccharide on a microbe’s surface. An antibody is the response, not the trigger; carcinogens cause cancer and mutagens damage DNA.
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