Immunology Practice Questions

Q: Activation of naïve B lymphocytes by protein antigens is?

T cell dependent. ***T cell dependent*** - Activation of naive B lymphocytes by **protein antigens** requires help from **helper T cells (CD4+ T cells)**. - B cells act as **antigen-presenting cells (APCs)**, processing and presenting protein antigens via MHC class II to T cells. - This interaction leads to **T cell help** through cytokines and CD40-CD40L signaling, resulting in **class switching, somatic hypermutation, and memory B cell formation**. *T Cell independent* - **T-cell-independent activation** of B lymphocytes typically occurs in response to **non-protein antigens**, such as polysaccharides, lipopolysaccharides (LPS), or lipids. - These antigens have **repetitive epitopes** that can cross-link multiple B cell receptors simultaneously. - This activation does not require T cell help and often leads to a **weaker, shorter-lived immune response** with limited class switching and no memory B cells. *NK cell dependent* - **NK cells** (Natural Killer cells) are part of the innate immune system and primarily involved in **killing infected or cancerous cells**. - They do not directly participate in the activation of naive B lymphocytes in response to protein antigens. - NK cells function independently of antigen-specific recognition. *NK cell independent* - This term is **not relevant** to the classification of B cell activation mechanisms. - The key distinction in B cell activation is whether it is **T cell dependent or T cell independent**, not whether it involves NK cells. - NK cells are not part of the adaptive immune response pathway for B cell activation by protein antigens.

Q: The image of an immunoglobulin is shown below. Which type of immunoglobulin is it?

Immunoglobulin A (IgA). ***Immunoglobulin A (IgA)*** - The image depicts two Y-shaped immunoglobulin monomers linked by a central purple component, which represents the **J-chain**, and enveloped by a yellow structure, which represents the **secretory component**. This **dimeric** structure with a secretory component is characteristic of secretory IgA. - **Secretory IgA** is primarily found in mucosal secretions such as saliva, tears, breast milk, and gastrointestinal fluids, where it plays a crucial role in **mucosal immunity** by preventing pathogen adhesion. *Immunoglobulin G (IgG)* - IgG exists as a **monomer** (single Y-shaped unit) in its functional form. - It is the most abundant immunoglobulin in serum and plays a major role in **secondary immune responses** and can cross the placenta. *Immunoglobulin M (IgM)* - In serum, IgM typically exists as a **pentamer**, meaning five Y-shaped units are joined together by a J-chain, forming a star-like structure. - It is the first antibody produced in a **primary immune response** and is effective in complement activation. *Immunoglobulin E (IgE)* - IgE exists as a **monomer** and is primarily associated with **allergic reactions** and defense against parasites. - It binds to receptors on mast cells and basophils, triggering immune responses upon allergen exposure.

Q: Which interleukin is primarily responsible for inducing IgE production from B cells?

IL-4. ***IL-4*** - **IL-4** is the primary cytokine responsible for promoting B cell differentiation into **plasma cells** that produce **IgE antibodies**. - It plays a crucial role in the development of **allergic reactions** by stimulating IgE class switching. *IL-1* - **IL-1** is a pro-inflammatory cytokine primarily involved in the **innate immune response**, fever, and acute phase reactions. - It does not directly induce IgE production but can modulate immune responses in a broader context. *IL-3* - **IL-3** is a cytokine that primarily supports the growth and differentiation of **hematopoietic stem cells** in the bone marrow. - It is crucial for the development of various blood cell lineages but is not directly involved in IgE class switching. *IL-1 and IL-3* - While both **IL-1** and **IL-3** have important roles in immunity and hematopoiesis, neither directly induces **IgE production** from B cells. - **IL-4** is the specific and most significant interleukin for this function.

Q: Which antibody is not transmitted from mother to baby?

IgA antibodies. ***IgA antibodies*** - While IgA is found in breast milk and provides **passive immunity** to the infant's gastrointestinal tract, it is **not transferred across the placenta** to the fetus. - This antibody has a larger molecular structure and is primarily involved in **mucosal immunity**, making it unsuitable for transplacental transfer. *Diphtheria IgG antibodies* - **IgG antibodies**, including those for diphtheria, are actively transported across the **placenta** from mother to fetus during the third trimester. - This transfer provides the newborn with **passive immunity** against diphtheria during the first few months of life. *Tetanus IgG antibodies* - Similar to diphtheria IgG, **tetanus IgG antibodies** are efficiently transported across the **placenta** from mother to baby. - This offers crucial **passive protection** against tetanus, particularly important after birth. *Measles IgG antibodies* - **Measles IgG antibodies** from a vaccinated or previously infected mother cross the **placenta** to the fetus. - This maternal transfer provides temporary **passive immunity** to the newborn against measles.

Q: Which protein is produced by B lymphocytes and not synthesized in the liver?

Immunoglobulins. ***Immunoglobulins*** - **B lymphocytes** differentiate into **plasma cells**, which are the primary producers of **immunoglobulins (antibodies)**. - The liver is not involved in the synthesis of immunoglobulins; their production is a key function of the **immune system**. *Acute phase proteins* - **Acute phase proteins** are primarily synthesized in the **liver** in response to inflammation. - While they are part of the immune response, they are not produced by **B lymphocytes**. *Serum albumin* - **Serum albumin** is the most abundant protein in plasma and is exclusively synthesized by the **liver**. - It plays a crucial role in maintaining **oncotic pressure** and transporting various substances, but is not produced by B lymphocytes. *Hormones in plasma* - **Hormones in plasma** are diverse chemical messengers produced by various **endocrine glands** throughout the body. - While the liver can metabolize some hormones, it is not their primary site of synthesis, nor are B lymphocytes.

Q: What is required for precipitation in comparison to agglutination?

Soluble antigen. ***Soluble antigen*** - **Precipitation reactions** involve the interaction of antibodies with **soluble antigens** to form a detectable precipitate. - Unlike **agglutination**, which involves particulate antigens (e.g., cells), precipitation requires the antigen to be dissolved in a solution. *Increased temperature* - Most immunologic reactions, including precipitation and agglutination, are typically performed at **physiological temperatures** (e.g., 37°C) or room temperature. - An **increased temperature** is not a specific requirement that differentiates precipitation from agglutination. *Specific cofactor* - While some complex immunologic reactions might require **cofactors**, neither precipitation nor agglutination inherently requires a specific cofactor to occur. - The primary components are **antigen** and **antibody**. *Lower pH* - Both precipitation and agglutination reactions are sensitive to pH and typically occur within a **narrow pH range** close to neutral (e.g., pH 7.0-7.4). - A **lower pH** (acidic environment) could lead to antibody denaturation or non-specific aggregation, ultimately hindering the reaction rather than being a requirement.

Q: Haptens are immunogenic when they covalently bind to which type of carrier?

Protein carrier. ***Protein carrier*** - Haptens are small molecules that are **antigenic** but not **immunogenic** on their own; they acquire immunogenicity when covalently bound to a larger carrier molecule. - **Proteins** are highly effective carriers because their complex structures and multiple epitopes can induce strong T-cell help, which is crucial for a robust antibody response against the hapten. *Lipid carrier* - While some lipids can be antigenic (e.g., glycolipids), they generally do not serve as effective carriers for haptens to induce a strong adaptive immune response, especially T-cell-dependent responses. - **Lipids** are less likely to be processed and presented by MHC molecules in a way that generates potent helper T-cell activation. *Polysaccharide carrier* - Some polysaccharides can be immunogenic themselves (e.g., bacterial capsular polysaccharides) and can induce T-cell-independent antibody responses. - However, for haptens to become immunogenic and induce a **T-cell-dependent antibody response**, a protein carrier is typically required. *None of the above carrier* - This option is incorrect because haptens do require a carrier to become immunogenic, and specific types of carriers are more effective than others. - The type of carrier chosen significantly impacts the **strength and nature of the immune response** to the hapten.

Q: Which human IgG subclass has the highest serum concentration?

IgG1. ***IgG1*** - **IgG1** constitutes approximately **60-70%** of the total IgG in human serum, making it the most abundant subclass. - Its high concentration reflects its crucial role in **neutralizing toxins**, agglutinating viruses, and opsonizing bacteria for phagocytosis. *IgG2* - **IgG2** makes up about **20-30%** of total IgG and is primarily important in protecting against **polysaccharide-encapsulated bacteria**. - While significant, its serum concentration is notably lower than that of IgG1. *IgG3* - **IgG3** is the least abundant IgG subclass, accounting for only **5-8%** of total IgG, and is characterized by a shorter half-life. - Despite its low concentration, it is highly efficient in activating the **complement system** due to its flexible hinge region. *IgG4* - **IgG4** comprises approximately **3-6%** of total IgG and is unique for its ability to undergo **Fab arm exchange**, leading to bispecific antibodies. - It does not activate complement and is often associated with allergy and protection against parasitic infections, but its concentration is significantly less than IgG1.

Q: Which of the following does not stimulate active immunity?

Transplacental antibody transfer in newborn. ***Transplacental antibody transfer in newborn*** - This is a form of **passive immunity**, where pre-formed **antibodies from the mother** are transferred to the newborn, providing immediate but temporary protection. - It does not involve the newborn's own immune system generating an immune response or creating **memory cells**. *Subclinical infection* - Even without overt symptoms, a **natural infection** exposes the immune system to pathogens, triggering an active immune response and generating **memory cells**. - This leads to **long-term immunity** against future exposures to the same pathogen. *Clinical infection* - A **symptomatic natural infection** involves the immune system actively responding to the pathogen, producing antibodies and **memory cells**. - This process is the basis of **naturally acquired active immunity** and provides durable protection. *Vaccination* - Vaccines contain weakened or inactive forms of pathogens, or their components, which stimulate the immune system to produce **antibodies** and **memory cells** without causing disease. - This is an example of **artificially acquired active immunity**, providing long-lasting protection.

Q: To which part of an antigen do monoclonal antibodies specifically bind?

Specific epitope on the antigen. ***Specific epitope on the antigen*** - Monoclonal antibodies are designed to recognize and bind to a **unique, specific region** on an antigen, known as an **epitope**. - This high specificity is crucial for their clinical applications, such as targeted therapies and diagnostic tests. *Both the epitope and the paratope* - The **epitope** is the part of the antigen, while the **paratope** is the part of the antibody that binds to the epitope. - An antibody binds to an epitope, not to both itself and its own binding site. *None of the options* - This option is incorrect because there is a correct answer among the choices provided, which accurately describes the binding site of monoclonal antibodies. *Part of the antibody that binds to the epitope* - This describes the **paratope**, which is the antigen-binding site on the antibody, not the part of the antigen to which the antibody binds. - The question specifically asks about the part of the antigen.

Question 1

Activation of naïve B lymphocytes by protein antigens is?

Accepted Answer

T cell dependent

Answer

T Cell independent

Answer

NK cell dependent

Answer

NK cell independent

Question 2

The image of an immunoglobulin is shown below. Which type of immunoglobulin is it?

Accepted Answer

Immunoglobulin A (IgA)

Answer

Immunoglobulin G (IgG)

Answer

Immunoglobulin M (IgM)

Answer

Immunoglobulin E (IgE)

Question 3

Which interleukin is primarily responsible for inducing IgE production from B cells?

Accepted Answer

IL-4

Answer

IL-1 and IL-3

Answer

IL-3

Answer

IL-1

Question 4

Which antibody is not transmitted from mother to baby?

Accepted Answer

IgA antibodies

Answer

Tetanus IgG antibodies

Answer

Diphtheria IgG antibodies

Answer

Measles IgG antibodies

Question 5

Which protein is produced by B lymphocytes and not synthesized in the liver?

Accepted Answer

Immunoglobulins

Answer

Acute phase proteins

Answer

Serum albumin

Answer

Hormones in plasma

Question 6

What is required for precipitation in comparison to agglutination?

Accepted Answer

Soluble antigen

Answer

Increased temperature

Answer

Specific cofactor

Answer

Lower pH

Question 7

Haptens are immunogenic when they covalently bind to which type of carrier?

Accepted Answer

Protein carrier

Answer

Lipid carrier

Answer

Polysaccharide carrier

Answer

None of the above carrier

Question 8

Which human IgG subclass has the highest serum concentration?

Accepted Answer

IgG1

Answer

IgG2

Answer

IgG3

Answer

IgG4

Question 9

Which of the following does not stimulate active immunity?

Accepted Answer

Transplacental antibody transfer in newborn

Answer

Clinical infection

Answer

Vaccination

Answer

Subclinical infection

Question 10

To which part of an antigen do monoclonal antibodies specifically bind?

Accepted Answer

Specific epitope on the antigen

Answer

None of the options

Answer

Both the epitope and the paratope

Answer

Part of the antibody that binds to the epitope

Immunology — MCQs

Immunology — MCQs

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