Immunology Practice Questions

Q: Which of the following is considered a non-professional antigen presenting cell?

Fibroblast cells. ***Fibroblast cells*** - **Fibroblast cells** are considered **non-professional antigen-presenting cells** as they do not constitutively express **MHC class II molecules** or **co-stimulatory molecules (B7, CD80/CD86)**. - Under **chronic inflammatory conditions**, fibroblasts can be induced to express MHC class II and present antigens, but they lack the specialized machinery for efficient **T-cell activation** that professional APCs possess. - They represent a classic example of non-professional APCs alongside endothelial cells, keratinocytes, and other tissue cells. *Endothelial cells* - **Endothelial cells** can express **MHC class II molecules** and co-stimulatory molecules during **inflammation or infection**. - They function as **non-professional APCs** (or semi-professional APCs) and can activate T cells in specific contexts, particularly in vascular immunity. - Also considered a valid example of non-professional APCs. *Epidermal cells* - **Epidermal cells** (specifically **keratinocytes**) can express **MHC class II molecules** under inflammatory conditions and present antigens to T cells. - They act as **non-professional APCs** in the context of skin immunity. - Like fibroblasts and endothelial cells, they can present antigens but are less efficient than professional APCs (dendritic cells, macrophages, B cells). *Red blood cells* - **Red blood cells** are **anucleate cells** that completely **lack MHC molecules** (both class I and class II). - RBCs **cannot present antigens** and are not classified as antigen-presenting cells of any type. - They are structurally incapable of antigen presentation due to absence of nuclei and cellular machinery.

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: Which of the following is a specific feature of acquired immunity?

Immunological memory. ***Immunological memory*** - A key characteristic of **acquired immunity** is the ability to "remember" previous encounters with specific pathogens. - This memory leads to a more rapid and robust immune response upon subsequent exposure to the same pathogen. - This is the **defining feature** that distinguishes acquired immunity from innate immunity. *Affected by genetic makeup* - While genetic makeup can influence the *efficiency* of the acquired immune system, it is not a **specific feature** that distinguishes it from innate immunity. - **Both innate and acquired immunity** are affected by genetic factors, determining baseline resistance and immune response capability. *No antigen exposure* - **Acquired immunity** is specifically characterized by its *dependence* on antigen exposure to develop specific responses. - The phrase "no antigen exposure" describes how the **innate immune system** functions, providing immediate, non-specific protection without prior contact with a pathogen. *Immediate response* - **Innate immunity** provides an immediate, non-specific response to pathogens. - **Acquired immunity** takes time to develop (days to weeks) after initial antigen exposure, but provides a faster response upon re-exposure due to immunological memory.

Q: What is the Rose Waaler test used for?

Passive hemagglutination test. ***Passive hemagglutination test*** - The **Rose Waaler test** is a historical **rheumatoid factor (RF)** detection method based on **passive hemagglutination**. - It uses sheep red blood cells coated with a subagglutinating dose of rabbit anti-sheep red blood cell antibody to detect RF in patient serum. *Complement fixation test* - This assay detects the presence of **antibody** or **antigen** by observing whether **complement** is consumed in an antigen-antibody reaction. - The Rose Waaler test does not involve the measurement of complement consumption. *Precipitation in gel* - This technique, such as **immunodiffusion**, involves the formation of a visible **precipitate** when soluble antigens and antibodies diffuse through a gel matrix and meet at optimal concentrations. - The Rose Waaler test relies on agglutination of red blood cells, not precipitation in gel. *Ring precipitation* - A **ring precipitation test** involves layering an antigen solution over an antibody solution, creating an antigen-antibody complex visible as a **precipitate ring** at the interface of the two solutions. - This method is distinct from the Rose Waaler test which uses red blood cell agglutination.

Q: IgM appears in fetus at what gestational age -

20 weeks. ***20 weeks*** - The fetal immune system begins to develop around **20 weeks of gestation**, at which point the fetus starts producing its own **IgM antibodies**. - **IgM** is the first antibody isotype produced by the developing fetal **B lymphocytes** and is important for early immune responses. *10 weeks* - While some components of the immune system may start to differentiate earlier, **IgM production** at a functional level is not yet established at **10 weeks of gestation**. - At this early stage, the fetal immune system is still primarily in its **developmental phase**, with major organogenesis occurring. *30 weeks* - By **30 weeks**, the fetus has already been producing IgM for several weeks, and the immune system is more mature, capable of a more robust **antibody response**. - While **IgG** levels are significantly increasing due to maternal transfer at this stage, **IgM production** began earlier. *at birth* - At birth, a neonate has circulating **IgM antibodies**, which are indicative of prior fetal immune activation and are measurable in umbilical cord blood. - However, the initial production of **fetal IgM** occurs much earlier in gestation, not at the time of birth.

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: 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.

Question 1

Which of the following is considered a non-professional antigen presenting cell?

Accepted Answer

Fibroblast cells

Answer

Endothelial cells

Answer

Epidermal cells

Answer

Red blood cells

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

Which of the following is a specific feature of acquired immunity?

Accepted Answer

Immunological memory

Answer

Affected by genetic makeup

Answer

No antigen exposure

Answer

Immediate response

Question 7

What is the Rose Waaler test used for?

Accepted Answer

Passive hemagglutination test

Answer

Ring precipitation

Answer

Precipitation in gel

Answer

Complement fixation test

Question 8

IgM appears in fetus at what gestational age -

Accepted Answer

20 weeks

Answer

10 weeks

Answer

30 weeks

Answer

at birth

Question 9

What is required for precipitation in comparison to agglutination?

Accepted Answer

Soluble antigen

Answer

Increased temperature

Answer

Specific cofactor

Answer

Lower pH

Question 10

Which of the following does not stimulate active immunity?

Accepted Answer

Transplacental antibody transfer in newborn

Answer

Clinical infection

Answer

Vaccination

Answer

Subclinical infection

Immunology — MCQs

Immunology — MCQs

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