Immune System Questions and Answers

Q: Which is the only antibody that crosses the placenta?

The only antibody that crosses the placenta is IgG.IgG is actively carried across the placenta by neonatal Fc receptors on placental cells. It gives the newborn passive immunity for the first few months of life, against the infections the mother has antibodies to.IgM is a large pentamer that cannot cross, so IgM in a newborn's blood points to an infection acquired in the womb. IgA is secreted in mucus, saliva and breast milk, especially colostrum, reaching the baby by feeding rather than across the placenta. IgD is found mainly on the surface of B cells.

Q: Which of the following protects our body against disease-causing pathogens?

Correct answer: Immune systemThe 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.

Q: Which of the following systems protects our body against disease-causing microbes?

Correct answer: Immune systemThe 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.

Q: Which of the following statements is true about Passive Immunity?

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.

Q: AIDS is caused by

Correct answer: RNA virusHIV 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.

Q: Skin, body hair, cilia, eyelashes, the respiratory tract and the gastrointestinal tract are examples of ________.

Correct answer: Physical barrierThese 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.

Q: A person is injected with gammaglobulin against hepatitis B. It is

Correct answer: Artificially acquired passive immunityGammaglobulin 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.

Q: Humoral immunity is mediated by ______________

Correct answer: lymphocytesHumoral 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.

Q: Which of the following is not involved in eliciting an immune response?

Correct answer: BrainThe 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.

Q: Which of the following cells is involved in cell-mediated immunity?

Correct answer: T-cellsCell-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.

Which is the only antibody that crosses the placenta?

A.IgM
B.IgG
C.IgA
D.IgD

Exam Year(s)

RSMSSB - 2025, RSMSSB Lab Technician - 2025,

Answer: B

The only antibody that crosses the placenta is IgG.

IgG is actively carried across the placenta by neonatal Fc receptors on placental cells. It gives the newborn passive immunity for the first few months of life, against the infections the mother has antibodies to.

IgM is a large pentamer that cannot cross, so IgM in a newborn's blood points to an infection acquired in the womb. IgA is secreted in mucus, saliva and breast milk, especially colostrum, reaching the baby by feeding rather than across the placenta. IgD is found mainly on the surface of B cells.

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Which of the following protects our body against disease-causing pathogens?

A.Respiratory system
B.Immune system
C.Digestive system
D.Excretory system

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.

Discuss in Forum

Which of the following systems protects our body against disease-causing microbes?

A.Immune system
B.Digestive system
C.Excretory system
D.Respiratory system

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.

Discuss in Forum

Which of the following statements is true about Passive Immunity?

A.This immunity causes reactions
B.This immunity develops immediately
C.This immunity lasts only for a few weeks or months
D.All of the above.

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.

Discuss in Forum

AIDS is caused by

A.RNA virus
B.DNA virus
C.Herpes virus
D.Hepatitis virus

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.

Discuss in Forum

Skin, body hair, cilia, eyelashes, the respiratory tract and the gastrointestinal tract are examples of ________.

A.Physical barrier
B.Cellular barriers
C.Cytokine barriers
D.Physiological barriers

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.

Discuss in Forum

A person is injected with gammaglobulin against hepatitis B. It is

A.Artificially acquired passive immunity
B.Artificially acquired active immunity
C.Naturally acquired active immunity
D.Naturally acquired passive immunity

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.

Discuss in Forum

Humoral immunity is mediated by ______________

A.mast cells
B.neutrophils
C.lymphocytes
D.leukocytes

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.

Discuss in Forum

Which of the following is not involved in eliciting an immune response?

A.Thymus
B.Spleen
C.Brain
D.Lymph nodes

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.

Discuss in Forum

10.

Which of the following cells is involved in cell-mediated immunity?

A.T-cells
B.B-cells
C.Mast cells
D.Both T and B cells

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.

Discuss in Forum

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