Innate Immunity — MCQs
The acute inflammatory response is predominantly mediated by which type of immune cells?
Which feature is most consistent with chronic inflammation?
Which of the following is not true about innate immunity
What is the primary function of Langerhans' cells?
What are the characteristics of polymorphonuclear leukocytes (PMNs) in the oral cavity?
The immunoglobulins that can be transported across the placenta include:
Which of the following is not a component of innate immunity?
Caspase involved in activation of IL-1 is which of the following?
All of the following statements are true regarding neutrophil extracellular trapping (NET) except for which of the following?
A pregnant woman, whose niece contracted varicella while living in the same house, tested negative for serum antibodies to varicella. What does this result indicate?
Innate Immunity Indian Medical PG Practice Questions and MCQs
Question 1: The acute inflammatory response is predominantly mediated by which type of immune cells?
- A. T lymphocytes
- B. Neutrophils (Correct Answer)
- C. Both B and T lymphocytes
- D. B lymphocytes
Explanation: ***Neutrophils*** - **Neutrophils** are the **primary mediators** of the **acute inflammatory response**, being the first immune cells recruited to sites of injury or infection (usually within minutes to hours) [1], [3]. - They are **innate immune cells** that perform phagocytosis, release antimicrobial substances, and form neutrophil extracellular traps (NETs) to combat pathogens [1]. - Neutrophils constitute **50-70% of circulating leukocytes** and are the hallmark cells found in acute inflammation [3]. *T lymphocytes* - **T lymphocytes** are central to **cell-mediated immunity** in the adaptive immune response, requiring several days for activation and clonal expansion [2]. - They recognize specific antigens through TCRs and are not involved in the immediate, non-specific phase of acute inflammation. - T cells play roles in **chronic inflammation** and coordinating adaptive immunity, not acute responses. *B lymphocytes* - **B lymphocytes** mediate **humoral immunity** by producing antibodies during the adaptive immune response [1]. - Their activation, differentiation into plasma cells, and antibody production take days to weeks, making them irrelevant to the rapid acute inflammatory response. - B cells are not recruited to acute inflammatory sites in the initial phase. *Both B and T lymphocytes* - While both are critical for **adaptive immunity** and host defense, neither B nor T lymphocytes are primary mediators of acute inflammation [4]. - The acute inflammatory response relies on **innate immune cells** (neutrophils, macrophages, mast cells) for immediate, non-specific protection before adaptive immunity develops [4].
Question 2: Which feature is most consistent with chronic inflammation?
- A. Hyperemia
- B. Vasodilation
- C. Fibrosis (Correct Answer)
- D. Edema
Explanation: ***Fibrosis*** - **Fibrosis** is the excessive accumulation of connective tissue, often seen as a **scarring process**, which is a hallmark of chronic inflammation as the body attempts to repair damaged tissue. [1] - Unlike acute inflammation, which is characterized by immediate vascular changes and exudation, chronic inflammation involves persistent tissue injury and attempts at repair, leading to **fibroblast proliferation** and collagen deposition. [2] *Hyperemia* - **Hyperemia** is an active process involving increased blood flow to a tissue, which causes it to redden. - It is a prominent feature of **acute inflammation**, contributing to rubor (redness) and calor (heat). *Vasodilation* - **Vasodilation**, the widening of blood vessels, is a key component of the **acute inflammatory response**. - It increases blood flow to the inflamed area, contributing to the cardinal signs of **redness and warmth**. *Edema* - **Edema** refers to the accumulation of excess fluid in the interstitial spaces, often due to increased vascular permeability. - While it can occur in both acute and chronic inflammation, it is a particularly prominent and early feature of **acute inflammation** as fluid rushes to the site of injury. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 103-104. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 194-195.
Question 3: Which of the following is not true about innate immunity
- A. Memory is seen (Correct Answer)
- B. It is relatively non specific
- C. It is first line of defence
- D. It is present prior to antigenic exposure
Explanation: ***Memory is seen*** - Innate immunity is characterized by a **lack of immunological memory**, meaning it does not \"remember\" previous encounters with pathogens to mount a stronger, faster response. - This feature is a hallmark of **adaptive (acquired) immunity**, which develops memory cells after initial exposure. *It is relatively non specific* - Innate immune responses are **non-specific** and target broad categories of pathogens, rather than specific antigens. - It recognizes conserved structures on pathogens, known as **Pathogen-Associated Molecular Patterns (PAMPs)**, shared by many different microbes. *It is first line of defence* - Innate immunity serves as the **body's immediate and primary defense** against invading pathogens. - It provides rapid protection through physical barriers, cellular components, and soluble factors, often preventing infection before it takes hold. *It is present prior to antigenic exposure* - The components of innate immunity are **pre-existing and fully functional** before any exposure to pathogens or antigens. - This readiness allows for an **instantaneous response** upon microbial invasion, without requiring prior sensitization.
Question 4: What is the primary function of Langerhans' cells?
- A. Antigen presenting cells (Correct Answer)
- B. Involved in immune responses
- C. Phagocytosis of pathogens
- D. Keratinocyte production and maintenance
Explanation: ***Antigen presenting cells*** - Langerhans' cells play a critical role as **antigen presenting cells** (APCs) in the immune system, facilitating the activation of T-cells [1][2]. - They are found in the **epidermis** and are essential in initiating immune responses against pathogens [1][3]. *Seen in auto immune conditions* - While Langerhans' cells may be involved in autoimmune responses, they are not exclusively seen in these conditions. - Their primary function isn't linked to autoimmunity but rather to **immunological surveillance** and **antigen presentation** [1]. *Phagocytic cells* - Langerhans' cells are not primarily **phagocytic**, as their main role focuses on presenting antigens rather than directly engulfing pathogens [1]. - Phagocytic cells include macrophages and neutrophils, which are more involved in **directly consuming foreign particles**. *Seen in chronic infection* - Although Langerhans' cells can participate in the immune response during infections, they are not specifically characterized as being prominent in **chronic infections**. - Chronic infections are typically associated with different immune cell dynamics, involving other cells such as **plasma cells** and **T-cells**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 200. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 207-208. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1144.
Question 5: What are the characteristics of polymorphonuclear leukocytes (PMNs) in the oral cavity?
- A. PMNs function mainly as antigen-presenting cells in oral tissues.
- B. Granulocytes found in the gingival connective tissue.
- C. PMNs actively migrate to the gingival crevicular fluid as part of the immune response. (Correct Answer)
- D. None of the options.
Explanation: **PMNs actively migrate to the gingival crevicular fluid as part of the immune response.** - **Polymorphonuclear leukocytes (PMNs)**, primarily neutrophils, are highly motile phagocytes that play a crucial role in the innate immune response to oral microbes. - Their active migration into the **gingival crevicular fluid (GCF)** is a hallmark of the body's defense against bacterial plaque, forming a crucial first line of defense against periodontal pathogens. *Granulocytes found in the gingival connective tissue.* - While PMNs are granulocytes that reside in the **gingival connective tissue**, this statement alone does not fully encompass their dynamic role and key characteristics in the oral cavity. - Their most significant characteristic in the context of oral health is their **active migration** to the epithelial surface and into the GCF, not just their presence in the connective tissue. *PMNs function mainly as antigen-presenting cells in oral tissues.* - **PMNs** are primarily involved in **phagocytosis** and intracellular destruction of pathogens, not as primary antigen-presenting cells (APCs). - **Dendritic cells** and **macrophages** are the main APCs that bridge innate and adaptive immunity by presenting antigens. *None of the options.* - This option is incorrect because the statement regarding **PMNs** actively migrating to the **gingival crevicular fluid** accurately describes a major characteristic and function of these cells in oral immunity.
Question 6: The immunoglobulins that can be transported across the placenta include:
- A. IgA only
- B. Neither IgG nor IgA
- C. IgG only (Correct Answer)
- D. Both IgG and IgA
Explanation: ***IgG only*** - **IgG** is the only class of immunoglobulin that can actively be transported across the **placental barrier** from mother to fetus, providing passive immunity. - This transport is mediated by specialized receptors (FcRn) on placental cells, ensuring the fetus receives protection against pathogens. *IgA only* - **IgA** is primarily found in **mucosal secretions** (e.g., breast milk, tears, saliva) and plays a crucial role in mucosal immunity. - It does not significantly cross the placenta and therefore does not contribute to fetal immunity in utero. *Neither IgG nor IgA* - This statement is incorrect because **IgG** is well-established as being transported across the placenta. - Such an absence of maternal antibodies would leave the fetus highly vulnerable to infections during development and early life. *Both IgG and IgA* - While **IgG** readily crosses the placenta, **IgA** does not, making this option incorrect. - The primary route for IgA transfer to the infant is through **breast milk** after birth, providing crucial immunity for the newborn's gastrointestinal tract.
Question 7: Which of the following is not a component of innate immunity?
- A. Epithelial barriers
- B. NK cells
- C. Dendritic cells
- D. Helper T lymphocytes (Correct Answer)
Explanation: ***Helper T lymphocyte*** - Helper T lymphocytes are a crucial part of **adaptive immunity** [4], facilitating responses against pathogens. - They specifically activate B cells and cytotoxic T cells [2], unlike components of innate immunity, which respond nonspecifically. *NK cells* - Natural Killer (NK) cells are integral to **innate immunity** [1], targeting infected or tumor cells without prior sensitization. - They play a role in the initial response to viral infections and can produce **cytokines** [2]. *Epithelial barriers* - Epithelial barriers act as the first line of defense in **innate immunity** [1], preventing pathogen entry. - They include physical and chemical barriers like skin and mucous membranes [3]. *Dendritic cells* - Dendritic cells are key antigen-presenting cells involved in **innate immunity** [1] and link to adaptive immunity. - They capture and present antigens [2], activating T cells to mount an immune response. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 194-196. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 207-208. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 152-153. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 196-198.
Question 8: Caspase involved in activation of IL-1 is which of the following?
- A. Caspase 5
- B. Caspase 1 (Correct Answer)
- C. Caspase 8
- D. Caspase 3
Explanation: ***Caspase 1*** - **Caspase 1** (also known as interleukin-1 beta converting enzyme or ICE) is the primary caspase responsible for the proteolytic cleavage and activation of pro-IL-1β and pro-IL-18 into their mature, active forms. - This activation occurs within the **inflammasome complex**, a multiprotein oligomer that assembles in response to various pathogens and danger signals. *Caspase 5* - While **Caspase 5** is an inflammatory caspase, similar to Caspase 1, it primarily functions in the direct activation of pro-IL-1β in certain contexts, particularly in response to *Gram-negative bacteria* through the non-canonical inflammasome. - However, **Caspase 1** is the canonical and most well-known activator of IL-1 in the classical inflammasome pathway. *Caspase 8* - **Caspase 8** is a key **initiator caspase** in the extrinsic pathway of apoptosis, activated by death receptors like Fas and TNF receptors. - Its primary role is in **apoptotic signaling** and it is not directly involved in the proteolytic activation of IL-1. *Caspase 3* - **Caspase 3** is a major **effector caspase** in both the intrinsic and extrinsic pathways of apoptosis. - It executes apoptosis by cleaving numerous cellular substrates and is not directly involved in the **processing of cytokines** like IL-1.
Question 9: All of the following statements are true regarding neutrophil extracellular trapping (NET) except for which of the following?
- A. It is detected in blood during sepsis
- B. It is chromatin with antibacterial enzymes
- C. Mitochondrial DNA is seen (Correct Answer)
- D. It is produced in response to bacterial infection
Explanation: ***Mitochondrial DNA is seen*** - NETs (Neutrophil Extracellular Traps) are made primarily of **nuclear chromatin**, not mitochondrial DNA [2]. - The main purpose of NETs is to trap and kill pathogens, focusing on **nuclear genetic material** rather than mitochondrial components. *It is detected in blood during sepsis* - NETs can indeed be found in the **circulation during sepsis**, serving as a defense mechanism against infections. - Their presence in blood indicates an **active immune response**, particularly in severe systemic infections. *It is produced in response to bacterial infection* - NET formation is a known response to **bacterial infections**, as neutrophils deploy them to capture and neutralize pathogens. - This process helps in controlling infections, showcasing the importance of NETs in **innate immunity**. *It is chromatin with antibacterial enzymes* - NETs consist primarily of **decondensed chromatin**, embedded with **antimicrobial proteins** and enzymes to combat pathogens [1][2]. - This characteristic underscores their role in targeting and eliminating invading microorganisms effectively. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 91-92. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 92-93.
Question 10: A pregnant woman, whose niece contracted varicella while living in the same house, tested negative for serum antibodies to varicella. What does this result indicate?
- A. She is susceptible to zoster
- B. She is immune to zoster
- C. She is immune to chicken pox
- D. She is susceptible to chickenpox (Correct Answer)
Explanation: ***She is susceptible to chickenpox*** - A negative test for serum antibodies to varicella indicates a **lack of protective immunity** to the varicella-zoster virus (VZV). - This woman has not previously been infected with VZV or vaccinated, making her **susceptible to primary infection (chickenpox)** upon exposure. *She is susceptible to zoster* - **Zoster (shingles)** is caused by the **reactivation of latent VZV** in individuals who have previously had chickenpox. - Since she tested negative for antibodies, she has not had chickenpox and thus **cannot harbor latent VZV** to reactivate. *She is immune to zoster* - Immunity to zoster implies that she has had chickenpox and subsequently developed a robust immune response to prevent viral reactivation. - A negative antibody test directly contradicts this, as it signifies no prior exposure or immune response. *She is immune to chicken pox* - Immunity to chickenpox is established by the presence of **varicella antibodies**, which are absent in this case. - A negative antibody result means she is **not immune** and is therefore at risk of contracting chickenpox if exposed.
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