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Question 1
Incorrect
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Which of the following statements is correct with regards to immunoglobulin?
Your Answer: The constant region on light chains can be either alpha or beta.
Correct Answer: The isotype of immunoglobulin is determined by the heavy chain.
Explanation:The composition of immunoglobulin molecules is two identical heavy and two identical light chains. These chains are linked by disulphide bridges and are each have highly variable regions which give the immunoglobulin its specificity. In addition, they have constant regions and there is virtual complete correspondence in amino acid sequence in all antibodies of a given isotype.
Five isotypes of immunoglobulin exist – these are IgG, IgA, IgM, IgE and IgD. They are determined by the heavy chain (gamma, alpha, mu, epsilon or delta respectively). The light chains are either kappa or lambda. -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 2
Correct
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In which of the following would you NOT typically see a neutropaenia:
Your Answer: Asplenism
Explanation:Causes of neutropaenia:
Drug-induced (e.g. chemotherapy, chloramphenicol, co-trimoxazole, phenytoin, carbamazepine, carbimazole, furosemide, chloroquine, clozapine, some DMARDs)
Benign (racial or familial)
Cyclical
Immune (e.g. SLE, Felty’s syndrome, hypersensitivity and anaphylaxis)
Leukaemia
Infections (e.g. HIV, hepatitis, fulminant bacterial infection)
General Pancytopaenia
Hypersplenism, aplastic anaemia, malignant infiltration of bone marrow, megaloblastic anaemia, chemotherapy, myelodysplasia -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 3
Incorrect
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What proportion of peripheral blood leukocytes are monocytes?
Your Answer: < 1%
Correct Answer: 5 - 10%
Explanation:Monocytes account for around 5 to 10% of peripheral white cells. Monocytes in peripheral blood are generally bigger than other leukocytes and feature a large central oval or indented nucleus with clumped chromatin. The abundant cytoplasm staining blue and containing numerous fine vacuoles gives the appearance of ground glass. Cytoplasmic granules are another type of granule.
Monocytes evolve from the granulocyte-macrophage progenitor to become monoblasts, promonocytes, monocytes, and tissue macrophages (in increasing order of maturity). Monocytes only stay in the bone marrow for a short time before exiting to circulate in the bloodstream for 20-40 hours before becoming macrophages.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 4
Incorrect
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Which of the following best describes the process of opsonisation:
Your Answer: The coating of foreign particles with antibodies that aid cytotoxic killing
Correct Answer: The coating of foreign particles with molecules which allow easier recognition of that cell by phagocytes
Explanation:An opsonin is any molecule that enhances phagocytosis by marking an antigen for an immune response, for example, immunoglobulin or complement. Opsonisation is the molecular mechanism whereby molecules, microbes, or apoptotic cells are chemically modified to have a stronger attraction to the cell surface receptors on phagocytes and natural killer cells. With the antigen coated in opsonins, binding to immune cells is greatly enhanced. Opsonisation also mediates phagocytosis via signal cascades from cell surface receptors.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 5
Correct
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The following are all examples of type IV hypersensitivity EXCEPT for:
Your Answer: Extrinsic allergic alveolitis
Explanation:Examples of type IV reactions includes:
Contact dermatitis
Hashimoto’s thyroiditis
Primary biliary cholangitis
Tuberculin skin test (Mantoux test)
Chronic transplant rejection
Granulomatous inflammation (e.g. sarcoidosis, Crohn’s disease) -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 6
Incorrect
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Regarding T helper cells, which of the following statements is CORRECT:
Your Answer: They initiate cytotoxic killing of target cells.
Correct Answer: They form the vast majority (about 75%) of the total circulating T-cell population.
Explanation:CD4+ T-cells (Helper T cells)Recognise antigen only in association with HLA class II molecules (found on antigen presenting cells (APCs) e.g. dendritic cells, B-cells; present exogenous antigens that have been phagocytosed/endocytosed into intracellular vesicles)Form most of the circulating T-cell population (about 75%)Secrete cytokines (e.g. IFN-gamma) which are required for recruitment and activation of other immune cells such as macrophages, T cytotoxic cells and NK cells and for the activation of and production of immunoglobulin from B-cells
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 7
Correct
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Which of these immunoglobulin molecules can cross the placenta?
Your Answer: IgG
Explanation:An important mechanism that provides protection to the foetus is placental transfer of maternal IgG antibodies while his/her humoral response is inefficient. The only antibody class that significantly crosses the human placenta is IgG.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 8
Incorrect
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Which of the following is NOT typically associated with eosinophilia:
Your Answer: Hodgkin lymphoma
Correct Answer: Whooping cough
Explanation:An eosinophil leucocytosis is defined as an increase in blood eosinophils above 0.4 x 109/L.It is most frequently due to:
Allergic diseases (e.g. bronchial asthma, hay fever, atopic dermatitis, urticaria)
Parasites (e.g. hookworm, ascariasis, tapeworm, schistosomiasis)
Skin diseases (e.g. psoriasis, pemphigus, urticaria, angioedema)
Drug sensitivity -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 9
Correct
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The most important Complement protein for antigen opsonization is:
Your Answer: C3b
Explanation:Phagocytosis is largely responsible for depletion of cells coated with antibodies. Cells opsonized by IgG antibodies are recognized by phagocyte Fc receptors, which are specific for the Fc portions of some IgG subclasses. In addition, when IgM or IgG antibodies are deposited on the surfaces of cells, they may activate the complement system by the classical pathway. Complement activation generates by-products, mainly C3b and C4b, which are deposited on the surfaces of the cells and recognized by phagocytes that express receptors for these proteins. The net result is phagocytosis of the opsonized cells and their destruction.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 10
Correct
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The following are all examples of type II hypersensitivity EXCEPT for:
Your Answer: Post-streptococcal glomerulonephritis
Explanation:Examples of type II reactions include:
Incompatible blood transfusions
Haemolytic disease of the newborn
Autoimmune haemolytic anaemias
Goodpasture’s syndrome
Rheumatic heart disease
Bullous pemphigoid -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 11
Correct
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Approximately what proportion of lymphocytes are B-cells:
Your Answer: 0.2
Explanation:B-cells (20% of lymphocytes) mature in the bone marrow and circulate in the peripheral blood until they undergo recognition of antigen. B-cell immunoglobulin molecules synthesised in the cell are exported and bound to the surface membrane to become the B-cell receptor (BCR) which can recognise and bind to a specific antigen (either free or presented by APCs). The BCR is also important for antigen internalisation, processing and presentation to T helper cells. Most antibody responses require help from antigen-specific T helper cells (although some antigens such as polysaccharide can lead to T-cell independent B-cell antibody production). When the B-cell is activated, the receptor itself is secreted as free soluble immunoglobulin and the B-cell matures into a memory B-cell or a plasma cell (a B-cell in its high-rate immunoglobulin secreting state). Plasma cells are non-motile and are found predominantly in the bone marrow or spleen. Most plasma cells are short-lived (1 – 2 weeks) but some may survive much longer. A proportion of B-cells persist as memory cells, whose increased number and rapid response underlies the augmented secondary response of the adaptive immune system.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 12
Correct
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Which of the following does NOT typically cause a neutrophil leucocytosis:
Your Answer: Glandular fever
Explanation:Causes of neutrophil leucocytosis:
Bacterial infection
Inflammation and tissue necrosis (e.g. cardiac infarct, trauma, vasculitis, myositis)
Metabolic disorders (e.g. uraemia, acidosis, eclampsia, gout)
Pregnancy
Acute haemorrhage or haemolysis
Neoplasms of all types
Drugs (e.g. corticosteroid therapy, lithium, tetracyclines)
Asplenia
Myeloproliferative disorders (e.g. CML, essential thrombocythaemia, polycythaemia vera, myelofibrosis)
Rare inherited disorders -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 13
Correct
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Eosinophils comprise what percentage of circulating white cells:
Your Answer: 1 - 3%
Explanation:Eosinophils comprise 1 – 3% of circulating white cells. Eosinophils are similar to neutrophils, except that the cytoplasmic granules are coarser and more deeply red staining, and there are rarely more than three nuclear lobes. They are less motile, but longer lived. They enter inflammatory exudates and have a special role in allergic responses, defence against parasites and removal of fibrin formed during inflammation. Thus they play a role in local immunity and tissue repair.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 14
Correct
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In all of the following conditions, lymphocytosis typically occurs except for:
Your Answer: Corticosteroid therapy
Explanation:In infants and young children, lymphocytosis often occurs in response to infections that would normally produce a neutrophil reaction in adults.
Lymphocytosis occurs in:
1. Viral infections (e.g. infectious mononucleosis, HIV, rubella, mumps, viral hepatitis, cytomegalovirus, herpes simplex or zoster)
2. Bacterial infections (e.g. pertussis, tuberculosis, toxoplasmosis, syphilis)
3. Chronic lymphoid leukaemias
4. Acute lymphoblastic leukaemias
5. Non-Hodgkin lymphoma
6. Thyrotoxicosis -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 15
Correct
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Which of the following is the most abundant peripheral blood leucocyte:
Your Answer: Neutrophils
Explanation:Neutrophils are the most abundant peripheral blood leucocyte, comprising about 50 – 70% of circulating white cells. Neutrophils have a characteristic dense nucleus consisting of between two and five lobes, and a pale cytoplasm with an irregular outline containing many fine pink-blue or grey-blue granules. The granules are divided into primary, which appear at the promyelocyte stage, and secondary, which appear at the myelocyte stage and predominate in the mature nucleus. Both types of granule are lysosomal in origin; the primary contains myeloperoxidase and other acid hydrolases; the secondary contains lactoferrin, lysozyme and other enzymes. The lifespan of neutrophils in the blood is only 6 – 10 hours. In response to tissue damage, cytokines and complement proteins, neutrophils migrate from the bloodstream to the site of insult within minutes, where they destroy pathogens by phagocytosis.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 16
Correct
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C3 deficiency leads to particular susceptibility of infection with which of the following:
Your Answer: Encapsulated bacteria
Explanation:Macrophages and neutrophils have C3b receptors and they phagocytose C3b-coated cells. C3 deficiency thus leads to increased susceptibility of infection with encapsulated organisms (e.g. S. pneumoniae, H. influenzae).The early stages of the complement cascade leading to coating of the cells with C3b can occur by two different pathways:The classical pathway usually activated by IgG or IgM coating of cellsThe alternative pathway which is more rapid and activated by IgA, endotoxin and other factors
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 17
Correct
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Which of the following best describes a natural killer cell:
Your Answer: A large granular lymphocyte that kills by inducing target cell apoptosis.
Explanation:Natural killer (NK) cells are cytotoxic CD8 positive cells that lack the T-cell receptor. They are large cells with cytoplasmic granules. NK cells are designed to kill target cells that have a low level of expression of HLA class I molecules, such as may occur during viral infection or on a malignant cell. NK cells do this by displaying several receptors for HLA molecules on their surface. When HLA is expressed on the target cell these deliver an inhibitory signal into the NK cell. When HLA molecules are absent on the target cell this inhibitory signal is lost and the NK cell can then kill its target. In addition, NK cells display antibody-dependent cell-mediated cytotoxicity. In this, antibody binds to antigen on the surface of the target cell and then NK cells bind to the Fc portion of the bound antibody and kill the target cell.
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This question is part of the following fields:
- Immune Responses
- Pathology
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SESSION STATS - PERFORMANCE PER SPECIALTY
