Q.1 What is the basic definition of an antigen?
A substance that always causes disease
A molecule that binds to an antibody or T-cell receptor
A protein produced by the immune system
A molecule that provides energy to immune cells
Explanation - An antigen is any substance that can be specifically recognized by the adaptive immune system, particularly antibodies or T-cell receptors.
Correct answer is: A molecule that binds to an antibody or T-cell receptor
Q.2 Which of the following properties makes a substance more immunogenic?
Low molecular weight
High molecular weight
Simple chemical structure
Self-origin
Explanation - Larger molecules are generally more immunogenic because they are more complex and provide more epitopes for immune recognition.
Correct answer is: High molecular weight
Q.3 What is an epitope?
The entire antigen molecule
A fragment of an antibody
The specific part of an antigen recognized by the immune system
A type of cytokine
Explanation - Epitopes, also called antigenic determinants, are the precise regions on an antigen that antibodies or T-cell receptors bind to.
Correct answer is: The specific part of an antigen recognized by the immune system
Q.4 Which of the following is a hapten?
A small molecule that is immunogenic by itself
A small molecule that becomes immunogenic only when attached to a carrier
A large protein antigen
A type of cytokine
Explanation - Haptens are small molecules that cannot induce an immune response alone but can do so when bound to a larger carrier protein.
Correct answer is: A small molecule that becomes immunogenic only when attached to a carrier
Q.5 Which of the following is most likely to act as a strong immunogen?
A lipid molecule
A simple carbohydrate
A complex protein
A nucleotide
Explanation - Proteins are usually the strongest immunogens because of their structural complexity and ability to be processed and presented by antigen-presenting cells.
Correct answer is: A complex protein
Q.6 Which factor does NOT typically affect immunogenicity?
Molecular size
Dose of antigen
Route of administration
Color of the antigen
Explanation - Immunogenicity depends on size, dose, route, and chemical complexity of an antigen, not its color.
Correct answer is: Color of the antigen
Q.7 Self-antigens usually do not provoke immune responses due to:
Tolerance
Immunogenicity
Cross-reactivity
Antigenicity
Explanation - The immune system usually develops tolerance to self-antigens to avoid autoimmune reactions.
Correct answer is: Tolerance
Q.8 Which of the following best describes immunogenicity?
Ability to bind specifically to antibodies
Ability to trigger an immune response
Ability to prevent infections
Ability to neutralize toxins
Explanation - Immunogenicity refers to the ability of a substance to induce an immune response, while antigenicity is the ability to bind to immune receptors.
Correct answer is: Ability to trigger an immune response
Q.9 What is the difference between an antigen and an immunogen?
All antigens are immunogens
All immunogens are antigens
Antigens cannot bind to antibodies
Immunogens cannot induce immunity
Explanation - While all immunogens are antigens, not all antigens are immunogens. Some antigens bind to immune receptors without inducing an immune response.
Correct answer is: All immunogens are antigens
Q.10 Which of the following is a T-independent antigen?
Polysaccharides
Peptides
Proteins
Lipids with carrier
Explanation - Polysaccharides can directly stimulate B-cells without T-cell help, making them T-independent antigens.
Correct answer is: Polysaccharides
Q.11 Which property of proteins makes them better immunogens compared to lipids?
They are smaller molecules
They have more structural complexity
They cannot be degraded
They are hydrophobic
Explanation - Proteins’ structural complexity and ability to be processed and presented make them strong immunogens.
Correct answer is: They have more structural complexity
Q.12 Which class of molecules is generally the least immunogenic?
Proteins
Polysaccharides
Lipids
Nucleic acids
Explanation - Lipids are generally poor immunogens unless conjugated with proteins or other carriers.
Correct answer is: Lipids
Q.13 Which of the following is an example of a complete antigen?
Dinitrophenol (DNP)
Ovalbumin
Penicillin alone
Vitamin B12
Explanation - Complete antigens can elicit an immune response on their own; proteins like ovalbumin are complete antigens, unlike small haptens.
Correct answer is: Ovalbumin
Q.14 The region of an antibody that binds to an antigen is called:
Epitope
Fab region
Fc region
Hinge region
Explanation - The Fab (fragment antigen-binding) region of the antibody interacts with antigen epitopes.
Correct answer is: Fab region
Q.15 Which antigen property increases the likelihood of T-cell dependent activation?
Being a small molecule
Being a large protein
Being a self-antigen
Being a lipid
Explanation - Large, complex proteins usually require T-cell help for B-cell activation and antibody production.
Correct answer is: Being a large protein
Q.16 Antigen-presenting cells (APCs) mainly present antigenic peptides via:
Antibodies
MHC molecules
Complement proteins
Cytokines
Explanation - APCs process antigens and present them on MHC molecules for recognition by T-cells.
Correct answer is: MHC molecules
Q.17 The capacity of an antigen to bind specifically with the products of the immune response is called:
Immunogenicity
Antigenicity
Tolerance
Cross-reactivity
Explanation - Antigenicity is the ability to bind specifically to antibodies or T-cell receptors, whereas immunogenicity is the ability to induce an immune response.
Correct answer is: Antigenicity
Q.18 Why are polysaccharides considered less immunogenic compared to proteins?
They are unstable molecules
They are too large
They lack structural complexity
They are easily degraded
Explanation - Polysaccharides are less complex structurally compared to proteins, reducing their immunogenicity.
Correct answer is: They lack structural complexity
Q.19 Which immune cells recognize antigen presented with MHC class II?
Cytotoxic T-cells (CD8+)
Helper T-cells (CD4+)
B-cells
NK cells
Explanation - CD4+ helper T-cells recognize antigen fragments presented by MHC class II molecules on APCs.
Correct answer is: Helper T-cells (CD4+)
Q.20 Which of the following best describes cross-reactivity?
When an antigen cannot be recognized
When an antibody reacts with similar epitopes on different antigens
When T-cells fail to activate
When antigens degrade quickly
Explanation - Cross-reactivity occurs when antibodies or T-cell receptors bind to epitopes that resemble the original antigen.
Correct answer is: When an antibody reacts with similar epitopes on different antigens
Q.21 Which of the following increases immunogenicity the most?
High molecular weight and complex structure
Small size and simplicity
Being self-derived
Being lipid-based
Explanation - Immunogenicity improves with higher molecular weight and structural complexity, as these present more epitopes.
Correct answer is: High molecular weight and complex structure
Q.22 Which organ is primarily responsible for T-cell maturation that recognizes antigens?
Bone marrow
Spleen
Thymus
Liver
Explanation - The thymus is responsible for T-cell maturation, including selection processes that ensure proper antigen recognition.
Correct answer is: Thymus
Q.23 Which of the following best defines a neoantigen?
A self-antigen recognized during development
A newly formed antigen resulting from mutation
An antigen derived from food
A small hapten
Explanation - Neoantigens arise due to genetic mutations, commonly in cancer, and are recognized as foreign by the immune system.
Correct answer is: A newly formed antigen resulting from mutation
Q.24 What makes adjuvants useful in vaccines?
They reduce antigen dose
They prevent antigen degradation
They enhance the immune response to the antigen
They act as antigens themselves
Explanation - Adjuvants boost immunogenicity of vaccines by enhancing antigen presentation and stimulating innate immunity.
Correct answer is: They enhance the immune response to the antigen
Q.25 Which antigen property is MOST important for recognition by T-cells?
Solubility in water
Ability to bind MHC molecules
High lipid content
Being a hapten
Explanation - For T-cells to recognize antigens, they must be processed and presented with MHC molecules.
Correct answer is: Ability to bind MHC molecules