Free Immunology MCQs with Answers

• A. Epinephrine
• B. Steroids
• C. Anti histamines
• D. Antibiotics

Explanation: Epinephrine is given first because it rapidly reverses airway obstruction, bronchospasm, vasodilation and hypotension in anaphylaxis.

• A. Hapten
• B. Carrier
• C. Super antigen
• D. Toxin

Explanation: Penicillin is a small molecule that becomes immunogenic after binding to a host protein, so it acts as a hapten.

• A. Type I hypersensitivity
• B. Type II hypersensitivity
• C. Type III hypersensitivity
• D. Type IV hypersensitivity

Explanation: Type I hypersensitivity is an immediate, IgE-mediated reaction: antigen cross-links IgE already fixed to mast cells and basophils, causing…

• A. IgD
• B. IgM
• C. IgA
• D. IgE

Explanation: IgE mediates immediate allergic reactions by binding mast cells and basophils; allergen exposure can therefore raise serum IgE.

• A. IgA
• B. IgD
• C. IgG
• D. IgM

Explanation: IgG is the predominant immunoglobulin in normal human serum, accounting for most circulating antibody and also crossing the placenta.

• A. Ig M
• B. Ig A
• C. Ig G
• D. Ig D

Explanation: IgG is the only major immunoglobulin that crosses the placenta in significant amounts, providing passive protection to the fetus and…

• A. B lymphocytes
• B. Erythrocytes
• C. T lymphocytes
• D. Antigen presenting cells (APC

Explanation: Acquired immunity depends chiefly on B lymphocytes, T lymphocytes and antigen-presenting cells.

• A. C3
• B. C5
• C. C2
• D. Protein B

Explanation: The classical, lectin and alternative complement pathways converge at activation of C3, beginning the common terminal pathway.

• A. complete antigen molecule
• B. Hapten
• C. Immunogen
• D. Smallest antigenic determinant

Explanation: An epitope is the smallest specific part of an antigen recognised by an antibody or immune receptor.

• A. Type I hypersensitivity
• B. Type II hypersensitivity
• C. Type III hypersensitivity
• D. Type IV hypersensitivity

Explanation: Post-streptococcal glomerulonephritis results from deposition of antigen-antibody immune complexes in the glomeruli, producing…

• A. IgG
• B. IgA
• C. IgM
• D. IgD

Explanation: IgG is the monoclonal immunoglobulin most often produced in multiple myeloma, although IgA is the next most frequent type.

• A. Antigen recognition by B cells
• B. Localization protection in external secretion
• C. Compliment activation
• D. Reagin activity

Explanation: IgD is present mainly on the surface of naïve B cells, where it acts with IgM as a B-cell antigen receptor.

• A. One Fc fragment and two Fab fragments
• B. One Fc fragment and four Fab fragments
• C. Two Fc fragments and two Fab fragments
• D. Two Fc fragment and one Fab fragment

Explanation: Papain cleaves IgG above its hinge region, producing two antigen-binding Fab fragments and one crystallisable Fc fragment.

• A. Payers patch
• B. Lymph node
• C. Thymus
• D. Busra of Fabricius

Explanation: T lymphocytes mature in the thymus, where they undergo selection for appropriate T-cell receptors and self-tolerance.

• A. MHC I
• B. MHC II
• C. MHC III
• D. B-cell receptor

Explanation: CD4-positive helper T cells recognise peptide antigens presented by MHC class II molecules on professional antigen-presenting cells.

• A. Type I
• B. Type II
• C. Type III
• D. Type IV

Explanation: Graves disease is a type II hypersensitivity because IgG autoantibodies stimulate the TSH receptor on thyroid cells.

• A. B-cells
• B. Active T cells
• C. NK cells
• D. Plasma cells

Explanation: Type IV hypersensitivity is delayed and cell-mediated, relying mainly on sensitised T lymphocytes rather than antibodies.

• A. Transfer of antibody from mother to child is through colostrum and acquired passive immunity naturally
• B. Injection of antibodies (Hepatitis) is artificially acquired passive immunity
• C. Antigenic stimulus given by vaccine (polio) is artificial active immunity
• D. All of the above

Explanation: Colostral antibody transfer is naturally acquired passive immunity, injected immunoglobulin is artificially acquired passive immunity, and…

• A. IgG1
• B. IgG2
• C. IgG3
• D. IgG4

Explanation: IgG1 is the most abundant human IgG subclass, comprising roughly two-thirds of total serum IgG.

• A. Production of interferon
• B. Lymphokine production
• C. Rosette formation
• D. All of the above

Explanation: T lymphocytes produce lymphokines and interferons, and their surface receptors allow them to form E-rosettes with sheep red blood cells.