Immune System Questions and Answers

Answer: C

Correct answer: AB

Group AB red cells carry both antigens, and the plasma consequently carries neither antibody - anti-A or anti-B would destroy the person’s own cells. Having no antibodies is what makes AB the universal recipient; group O, with neither antigen, is the universal donor.

Answer: B

Correct answer: Antibiotic

An antibiotic is by definition a substance produced by one organism - classically a mould or a soil bacterium - that inhibits the growth of another. Penicillin from Penicillium is the type case. An antibody is a protein made against a specific antigen, not a growth inhibitor of general use; an antigen provokes a response rather than inhibiting anything.

Answer: C

Correct answer: Hay fever

Hay fever (allergic rhinitis) is a type I hypersensitivity to inhaled allergens, usually pollen: IgE on mast cells in the nasal lining is cross-linked, histamine is released, and the result is sneezing, a runny nose and itching eyes. Enteric, yellow and trench fevers are infections - by Salmonella, a virus, and a Bartonella respectively.

Answer: D

Correct answer: All the above

Neutrophils, macrophages and lymphocytes are all white blood cells with defensive roles - the first two phagocytic and innate, the third specific and adaptive.

Answer: A

Correct answer: Rh+ male Rh- female

The risk arises only when an Rh-negative mother carries a child who may be Rh-positive, which needs an Rh-positive father. The first pregnancy usually passes safely; sensitisation occurs around delivery, and later Rh-positive pregnancies are then at risk of haemolytic disease. (Anti-D immunoglobulin given to the mother now prevents this, so the old advice has been overtaken.)

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.

Answer: B

Correct answer: Allergy

An allergy is an exaggerated immune response to something harmless - pollen, a food, a drug. It is not an infection, since no pathogen is involved, and the damage is done by the reaction rather than by the substance itself.

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.

Answer: A

Correct answer: Vertebrates only

Acquired immunity - lymphocytes, antibodies, and memory of a specific antigen - is found only in vertebrates. Invertebrates and plants have effective innate defences, including phagocytic cells and antimicrobial peptides, but nothing that recognises one antigen and remembers it.

Answer: B

Correct answer: Vertebrates

Only vertebrates have the lymphocyte-based system that recognises a specific antigen and retains memory of it. Invertebrate defence is entirely innate, however elaborate.