What is not required in the innate immune responses?
Answer: D
Correct answer: previous contact
Innate immunity acts on the first encounter, because it recognises broad patterns shared by whole classes of microbe rather than one particular antigen. No previous contact is needed - and that is precisely what distinguishes it from acquired immunity, which must be primed before it can act.
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An Rh- woman married to Rh+ man gave birth to three children, one of which died of erythroblastosis foetalis. What are the genotypes of the woman and the man?
Answer: A
Correct answer: Rh- Rh-, Rh+ Rh-
Rh-negative is recessive, so the woman must be homozygous recessive. The man is Rh-positive, and since only one of the three children was affected he evidently passed the negative allele to the others - so he is heterozygous. Each child then has a one in two chance of being Rh-positive and so at risk.
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Antibodies are
Answer: A
Correct answer: Glycoproteins
An antibody is a protein with carbohydrate chains attached - a glycoprotein. Its four polypeptide chains, two heavy and two light, are held by disulphide bonds into the familiar Y, with the sugars on the constant region of the heavy chains, where they help determine how the antibody is handled once bound.
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Antibodies belong to which class of proteins?
Answer: C
Correct answer: Immunoglobulin
Antibodies are the immunoglobulins - the class of proteins defined by the fold that gives them their antigen-binding sites, and divided into IgG, IgM, IgA, IgE and IgD. They are neither structural, nor transport proteins, nor enzymes: they work by binding, not by catalysing.
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Macrophages are derived from
Answer: C
Correct answer: Monocytes
A monocyte circulates for a day or two, then leaves the blood, enters a tissue and matures into a macrophage. The same lineage gives the liver its Kupffer cells, the brain its microglia and the lung its alveolar macrophages.
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Active immunity is due to
Answer: C
Correct answer: Memory cells
What makes active immunity last is the pool of memory cells left behind after a response. They persist for years and, on meeting the same antigen again, produce a response that is faster, larger and of higher affinity - the basis of vaccination. Killer, helper and suppressor T cells all act during a response but do not carry its memory.
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Resistance developed in an individual as a result of antigenic stimulus is
Answer: B
Correct answer: Active acquired immunity
Resistance built in response to an antigenic stimulus - an infection or a vaccine - is active acquired immunity: the body made the response itself and retains memory cells. Passive immunity involves no antigenic stimulus at all, since the antibodies arrive ready-made.
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Memory cells are formed from
Answer: D
Correct answer: B-lymphocytes
When a B cell is activated it divides, and its descendants take two paths: most become plasma cells that secrete antibody now, while some become memory B cells that persist for years. (T cells leave memory cells too, but the classic antibody memory of a secondary response is the B cell’s.)
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Which of the following helps in the differentiation of the cells of the immune system?
Answer: B
Correct answer: Thymosin
Thymosin, secreted by the thymus, drives the maturation and differentiation of T lymphocytes. Cortisol and other steroids suppress immune activity rather than promote it, and thyroxine governs metabolic rate.
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Antibodies are produced by
Answer: C
Correct answer: Plasma cells
Plasma cells are activated B cells that have turned into antibody factories: an expanded endoplasmic reticulum and an output of thousands of molecules a second, all of one specificity. Histiocytes are tissue macrophages, mast cells release inflammatory mediators, and fibroblasts make connective tissue.
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