Leukocytes and Immune Function — MCQs
Which of the following does not cause granulomatous inflammation?
Cortisol increases all of the following components except:
Which of the following is not a component of innate immunity?
Which of the following cells will increase in case of parasite infection?
All are true regarding the development of T-cells, except?
The acute inflammatory response is predominantly mediated by which type of immune cells?
What are the characteristics of polymorphonuclear leukocytes (PMNs) in the oral cavity?
What is the primary function of Langerhans' cells?
The immunoglobulins that can be transported across the placenta include:
Which of the following can be absorbed without being broken down, especially in infants?
Leukocytes and Immune Function Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following does not cause granulomatous inflammation?
- A. Sarcoidosis
- B. Tuberculosis
- C. Pneumonia (Correct Answer)
- D. Histoplasmosis
Explanation: ***Pneumonia*** - **Pneumonia**, in its typical bacterial form, usually causes an **acute inflammatory response** with neutrophil infiltration in the alveoli [1], [2]. - While some atypical pneumonias can have chronic or granulomatous features, the term "pneumonia" alone generally refers to acute inflammation without granulomas. *Sarcoidosis* - **Sarcoidosis** is characterized by distinctive **non-caseating granulomas** in multiple organs, most commonly the lungs, lymph nodes, and skin [3], [4]. - The formation of these granulomas is a hallmark of the disease and is crucial for diagnosis [3]. *Tuberculosis* - **Tuberculosis** is classically characterized by the formation of **caseating granulomas** (tubercles) with central necrosis, surrounded by epithelioid macrophages and giant cells [2]. - The host immune response to *Mycobacterium tuberculosis* is primarily granulomatous, aiming to contain the infection. *Histoplasmosis* - **Histoplasmosis**, a fungal infection caused by *Histoplasma capsulatum*, often leads to the formation of **granulomas**, both caseating and non-caseating [2]. - The granulomatous response is an essential part of the host's defense mechanism against this intracellular pathogen. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 317-318. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 360. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 700-701. [4] 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. 198-200.
Question 2: Cortisol increases all of the following components except:
- A. Monocytes
- B. RBCs
- C. Platelets
- D. Eosinophils (Correct Answer)
Explanation: ***Eosinophils*** - Cortisol causes **eosinopenia** (a decrease in eosinophils) by increasing their sequestration in tissues and promoting their apoptosis. - This effect is a classic indicator of stress and can be observed in conditions of elevated endogenous or exogenous cortisol. *Monocytes* - Cortisol typically causes a **mild monocytosis** (increase in circulating monocytes), although this effect can vary. - It impacts the trafficking and differentiation of monocytes, leading to their transient increase in the bloodstream. *RBCs* - Cortisol can lead to a slight **increase in red blood cell (RBC) count** or hemoglobin concentration. - This effect is partly due to hemoconcentration and partly by promoting erythropoiesis. *Platelets* - Cortisol generally causes a **thrombocytosis** (increase in platelet count). - This effect is thought to be mediated by various factors, including cytokine interactions and direct effects on megakaryopoiesis.
Question 3: 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 4: Which of the following cells will increase in case of parasite infection?
- A. A: Lymphocyte
- B. D: Basophil
- C. C: Eosinophil (Correct Answer)
- D. B: Neutrophil
Explanation: ***Eosinophil*** - **Eosinophils** play a crucial role in the immune response against **parasitic infections**, particularly helminths. - They release cytotoxic granules containing **major basic protein**, **eosinophil cationic protein**, and other mediators that damage the parasites. *Lymphocyte* - **Lymphocytes** are primarily involved in adaptive immunity and are crucial for fighting viral infections and certain bacterial infections, but their increase is not a primary marker for parasitic infections. - While T-helper cells (a type of lymphocyte) can activate eosinophils, a direct increase in total lymphocytes is not the hallmark of parasitic infections. *Basophil* - **Basophils** are involved in allergic reactions and chronic inflammation, releasing histamine and other mediators. - While they can be activated during some parasitic infections, their increase is not as prominent or specific as that of eosinophils. *Neutrophil* - **Neutrophils** are the most abundant white blood cells and are the primary responders to acute bacterial infections and inflammation. - They are less effective against parasitic infections, which often require specialized immune responses.
Question 5: All are true regarding the development of T-cells, except?
- A. T-cells are formed in bone marrow
- B. In lymph nodes, T-cells are found in paracortical area
- C. Maturation of T-cells take place in thymus
- D. T-cells are located in mantle layer of spleen (Correct Answer)
Explanation: ***T-cells are located in mantle layer of spleen*** - The **mantle layer** (or marginal zone) of the spleen is primarily associated with **B-lymphocytes**, which are involved in antibody production. - While T-cells are present in the spleen, they are predominantly found in the **periarteriolar lymphoid sheath (PALS)**, which is part of the white pulp, rather than the mantle layer. *T-cells are formed in bone marrow* - **Hematopoietic stem cells** in the **bone marrow** are the progenitors of all blood cells, including lymphocytes. - These stem cells differentiate into **lymphoid stem cells**, which then travel to the thymus to become T-cells. *Maturation of T-cells take place in thymus* - **T-cell precursors** migrate from the bone marrow to the **thymus**, where they undergo a complex process of differentiation and selection. - In the thymus, T-cells acquire their **T-cell receptors (TCRs)** and undergo positive and negative selection to ensure they are self-MHC restricted and tolerant to self-antigens. *In lymph nodes, T-cells are found in paracortical area* - The **paracortical area** (or paracortex) of the lymph node is the **T-cell zone**, rich in T-lymphocytes and dendritic cells. - This region is crucial for the interaction between T-cells and antigen-presenting cells, initiating adaptive immune responses.
Question 6: 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 7: 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 8: 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 9: 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 10: Which of the following can be absorbed without being broken down, especially in infants?
- A. a-Dextrins
- B. Protein (Correct Answer)
- C. Sucrose
- D. Triglycerides
Explanation: ***Protein*** - In infants, particularly during the neonatal period, the intestinal epithelium exhibits increased **permeability** allowing for the absorption of intact proteins. - This phenomenon is crucial for the passive transfer of **maternal antibodies** (immunoglobulins) present in breast milk, providing temporary immunity to the infant. - This mechanism of intact protein absorption is known as **pinocytosis** and is especially prominent in the first few days of life. *a-Dextrins* - These are oligosaccharides derived from starch and require further enzymatic breakdown by **maltase-glucoamylase** before they can be absorbed as monosaccharides. - They cannot be absorbed intact, as their molecular size is too large to pass through the intestinal epithelial cells directly. *Sucrose* - Sucrose is a disaccharide that must be hydrolyzed into its constituent monosaccharides, **glucose and fructose**, by the enzyme **sucrase** in the brush border before absorption. - Intact sucrose molecules are too large to be absorbed across the intestinal wall. *Triglycerides* - Triglycerides are complex lipids that are first emulsified by bile salts and then hydrolyzed into **monoglycerides and free fatty acids** by pancreatic lipase. - These smaller components are then absorbed and re-esterified within the intestinal cells, rather than being absorbed as intact triglycerides.
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