KMU Past Paper Practice
Hypersensitivity, Immune Tolerance, Autoimmunity, Immunodeficiency and Immunomodulatory Drugs
3rd Year MBBS • 20 A-type Single Best Answer MCQs
MCQ 1
A 17-year-old boy with a family history of atopy is exposed to a new environmental allergen. He has no symptoms during the first exposure, but allergen-specific IgE becomes detectable afterward. Which cytokine activity most directly promotes this sensitization process?
Promotion of IgE production by IL-4 and IL-13
Th2-derived IL-4 and IL-13 promote B-cell switching toward IgE production, allowing IgE to bind mast cells and establish sensitization before later allergen exposure.
MCQ 2
A 28-year-old man presents with hemoptysis and renal dysfunction. Antibodies are directed against basement-membrane antigens in the lungs and kidneys. Which mechanism is most likely to produce tissue injury in this disorder?
Complement activation with leukocyte-mediated inflammation
Antibodies bound to fixed tissue antigens can activate complement and recruit inflammatory leukocytes, producing the type II tissue injury seen in Goodpasture syndrome.
MCQ 3
Several hours after an antigen is injected into the skin of a previously sensitized person, a painful localized area of edema, hemorrhage and inflammation develops at the injection site. Which reaction best explains this finding?
Arthus reaction
The Arthus reaction is a localized immune-complex reaction in which locally formed complexes activate complement and produce acute vascular inflammation.
MCQ 4
A medical student receives an intradermal test antigen. Forty-eight hours later, the site is firm and indurated because sensitized lymphocytes have recruited and activated inflammatory cells. Which effector mechanism is principally responsible?
Cytokine-mediated macrophage recruitment and activation
Delayed hypersensitivity can be mediated by sensitized CD4-positive T cells whose cytokines recruit and activate macrophages, producing induration after many hours.
MCQ 5
Trauma exposes a self-antigen that had previously been relatively inaccessible to circulating lymphocytes. An immune response against the newly exposed tissue subsequently develops. Which normal protective mechanism has been disrupted?
Limited exposure of lymphocytes to self-antigen
Relative sequestration of some self-antigens helps prevent autoreactive lymphocyte activation; tissue injury may expose these antigens and contribute to loss of tolerance.
MCQ 6
A patient receives hematopoietic stem cells containing mature donor lymphocytes. The donor cells recognize recipient antigens as foreign. Which additional circumstance is particularly important for development of graft-versus-host disease?
Failure of the recipient to eliminate donor lymphocytes
GVHD requires immunocompetent donor T cells, recipient antigens recognized as foreign and insufficient recipient immunity to remove the attacking donor lymphocytes.
MCQ 7
Two weeks after renal transplantation, a patient develops graft dysfunction. Biopsy demonstrates vascular injury, and circulating donor-specific antibodies are detected. Which mechanism most directly accounts for the graft damage?
Antibody-mediated injury to graft blood vessels
Acute rejection may have an antibody-mediated component in which newly formed donor-specific antibodies target graft endothelium and produce vascular injury.
MCQ 8
A 34-year-old woman develops fatigue, jaundice and anemia. Her erythrocytes are coated with autoantibodies and are removed predominantly by phagocytic cells. Which mechanism best accounts for the anemia?
Opsonization followed by phagocytic removal
In autoimmune hemolytic anemia, antibodies coat red cells and promote their recognition and removal by phagocytes, producing antibody-mediated cytopenia.
MCQ 9
A genetically susceptible patient develops autoimmune tissue injury after significant local tissue damage. Which event can most plausibly contribute to initiation of the abnormal immune response?
Release or alteration of self-antigens with inflammation
Tissue injury can expose or modify self-antigens and generate inflammatory signals that favor activation of previously harmless autoreactive lymphocytes.
MCQ 10
An infant develops recurrent infections and has markedly reduced thymic development. Serum immunoglobulin production is relatively less affected than cell-mediated immunity. Which category of immune defect is most consistent with this pattern?
Primary T-lymphocyte deficiency
Thymic developmental failure primarily impairs T-cell maturation and therefore cell-mediated immunity, as classically occurs in DiGeorge syndrome.
MCQ 11
A young adult has recurrent infections involving respiratory mucosal surfaces. Most major immune-cell populations are present, but one immunoglobulin class important for mucosal defense is deficient. Which disorder best fits this presentation?
Selective IgA deficiency
IgA is important at mucosal surfaces, so selective deficiency may present with recurrent respiratory or gastrointestinal infections despite otherwise preserved immunity.
MCQ 12
In a patient with chronic HIV infection, viral persistence continues despite progressive damage to helper T lymphocytes. Infection of which additional cell population contributes importantly to persistence of the virus?
Macrophages and related cells
HIV can infect macrophages and related cells in addition to CD4-positive T lymphocytes, contributing to viral persistence and continuing immune-system injury.
MCQ 13
A renal transplant recipient receiving a calcineurin inhibitor develops hypertension, increased hair growth and gingival overgrowth. Which drug is most likely responsible?
Cyclosporine
Cyclosporine can cause nephrotoxicity and hypertension and is classically associated with gingival overgrowth and increased hair growth.
MCQ 14
A patient undergoing organ transplantation receives a monoclonal antibody that reduces activation of T lymphocytes by targeting the alpha chain of the IL-2 receptor. Which agent has been administered?
Basiliximab
Basiliximab binds CD25, the alpha chain of the IL-2 receptor on activated T cells, and thereby reduces IL-2-driven lymphocyte proliferation.
MCQ 15
A patient with severe autoimmune disease receives a cytotoxic immunosuppressive drug. During follow-up, he develops painful hematuria caused by drug-related bladder toxicity. Which agent is most likely responsible?
Cyclophosphamide
Cyclophosphamide is a potent cytotoxic immunosuppressant whose important toxicities include bone-marrow suppression, infertility and hemorrhagic cystitis.
MCQ 16
A woman receiving an antimetabolite for chronic autoimmune disease develops oral mucosal injury, elevated liver enzymes and bone-marrow suppression. Which immunomodulating drug best matches this adverse-effect profile?
Methotrexate
Methotrexate has important immunomodulatory actions in autoimmune disease and can produce mucosal injury, hepatotoxicity and bone-marrow suppression.
MCQ 17
A patient with a chronic immune-mediated inflammatory disorder improves after starting a monoclonal antibody that neutralizes tumor necrosis factor. Several months later, a previously controlled latent infection becomes clinically active. Which treatment most likely contributed to this complication?
Anti-TNF monoclonal antibody therapy
TNF contributes to effective host defense, so therapeutic TNF blockade can increase susceptibility to serious infection and permit reactivation of latent infection.
MCQ 18
A patient with a condition requiring immune stimulation is prescribed a cytokine with antiviral, antiproliferative and immunomodulatory properties. Which class of agents best fits this description?
Interferons
Interferons are immunostimulatory cytokines with antiviral, antiproliferative and immune-modifying actions and have selected therapeutic uses.
MCQ 19
An immunostimulant is selected for a patient with a malignancy in which enhancement of cellular immune activity is desired. The drug acts by promoting activation and proliferation of T lymphocytes. Which mediator is being used therapeutically?
Interleukin-2
IL-2 promotes T-cell activation and proliferation and can therefore be used to enhance cellular antitumor immune responses in selected malignancies.
MCQ 20
A patient with a superficial bladder malignancy receives an immunomodulating agent directly into the bladder to provoke a local immune response against tumor cells. Which treatment is being used?
Intravesical BCG therapy
Intravesical BCG acts as an immunostimulant and generates a local antitumor immune response that can be therapeutically useful in selected bladder malignancies.