Lymphoid Organs and Immune System — MCQs
Lymphatic follicles are not seen in:
Which of the following is not a component of innate immunity?
All of the following are features of Lymph node histology except:
Biopsy of the exposed surface of the palatine tonsil reveals which type of tissue?
Which of the following statements regarding axillary lymph nodes is incorrect?
Cause of Farmer's lung -
What is the most common genetic factor associated with increased susceptibility to Neisseria infections?
Ligamentum flavum consists of which fibres:
Which of the following area is marked in the histology of lymph node? (AIIMS May 2017)
The tonsils are derived from:
Lymphoid Organs and Immune System Indian Medical PG Practice Questions and MCQs
Question 1: Lymphatic follicles are not seen in:
- A. Spleen
- B. Lymph node
- C. Tonsil
- D. Thymus (Correct Answer)
Explanation: ***Thymus*** - The thymus is primarily involved in **T-cell maturation** [1] and does not contain **lymphatic follicles**. - Its cortex and medulla are organized for T-cell education and selection, lacking the B-cell zones characteristic of follicles. *Spleen* - The **white pulp** of the spleen is rich in **lymphatic follicles**, which are sites of B-cell proliferation and differentiation. - These follicles are crucial for mounting immune responses against blood-borne pathogens. *Lymph node* - Lymph nodes are characterized by abundant **lymphatic follicles** in their cortex, containing primarily **B lymphocytes** [1]. - These follicles enlarge and form **germinal centers** during an active immune response. *Tonsil* - Tonsils are part of the **mucosa-associated lymphoid tissue (MALT)** and contain numerous **lymphatic follicles**. - These follicles help in initiating immune responses against pathogens entering through the oral cavity.
Question 2: 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 3: All of the following are features of Lymph node histology except:
- A. Both Efferent and Afferent are present
- B. Subcapsular sinus present
- C. Cortex and Medulla are present
- D. Red pulp and White pulp are present (Correct Answer)
Explanation: ***Red pulp and White pulp are present*** - **Red pulp** and **white pulp** are characteristic histological features of the **spleen**, not lymph nodes [1]. - The white pulp contains lymphoid follicles (PALS - periarteriolar lymphoid sheaths), while the red pulp is involved in filtering blood and destroying old red blood cells [1]. - This is the feature that does NOT belong to lymph node histology. *Both Efferent and Afferent are present* - Lymph nodes have multiple **afferent lymphatic vessels** that bring lymph into the node and usually one or two **efferent lymphatic vessels** that carry lymph away [2]. - This arrangement allows for efficient filtering of lymph and immune surveillance [2]. - This IS a feature of lymph nodes. *Subcapsular sinus present* - The **subcapsular sinus** is a space located directly beneath the capsule of the lymph node, which receives lymph from the afferent lymphatic vessels. - It contains a network of reticular fibers and macrophages, acting as the initial filtering area. - This IS a feature of lymph nodes. *Cortex and Medulla are present* - Lymph nodes are histologically divided into an outer **cortex** and an inner **medulla**. - The cortex contains lymphoid follicles (B-cell areas) and paracortical areas (T-cell areas), while the medulla consists of medullary cords and sinuses. - This IS a feature of lymph nodes.
Question 4: Biopsy of the exposed surface of the palatine tonsil reveals which type of tissue?
- A. Stratified squamous epithelium (Correct Answer)
- B. Simple squamous epithelium
- C. Simple columnar epithelium
- D. Pseudostratified columnar ciliated epithelium
Explanation: The palatine tonsils are part of the **oropharynx**, which is subjected to mechanical abrasion from food and drink. **Stratified squamous epithelium** provides robust protection against such friction and is characteristic of surfaces needing high wear resistance. *Simple squamous epithelium* - This type of epithelium is found in areas where **diffusion** or **filtration** is important, such as the lining of blood vessels (endothelium) and alveoli of the lungs. - It would not provide adequate protection for the exposed surface of the tonsil that is subject to frequent mechanical stress. *Simple columnar epithelium* - Characterized by cells taller than they are wide, often found in the **gastrointestinal tract** for absorption and secretion. - It lacks the multi-layered structure needed for protection against the abrasive forces typical in the oropharynx. *Pseudostratified columnar ciliated epithelium* - This epithelium is primarily found in the **respiratory tract**, where its cilia help move mucus and trapped particles. - While it offers some protection, its primary function is not mechanical resistance, and it is not found on the exposed surfaces of the palatine tonsils.
Question 5: Which of the following statements regarding axillary lymph nodes is incorrect?
- A. Posterior group lies along subscapular vessels
- B. Lateral group lies along lateral thoracic vessels (Correct Answer)
- C. Apical group is terminal lymph nodes
- D. Apical group lies along axillary vessels
Explanation: ***Lateral group lies along lateral thoracic vessels*** - The **lateral group** of axillary lymph nodes is located along the **axillary vein**, receiving lymph primarily from the upper limb [1]. - The **lateral thoracic vessels** are associated with the central and posterior groups of axillary lymph nodes, not the lateral group. *Posterior group lies along subscapular vessels* - The **posterior (subscapular) group** of axillary lymph nodes is indeed located along the **subscapular vessels**. - This group receives lymph from the posterior wall of the trunk and the posterior shoulder region. *Apical group is terminal lymph nodes* - The **apical group** (also known as the subclavian group) is considered the **terminal lymph nodes** of the axilla. - Lymph from all other axillary nodes eventually drains into the apical group before continuing to the supraclavicular nodes and then into the subclavian lymphatic trunk [2]. *Apical group lies along axillary vessels* - The **apical group** of axillary lymph nodes is situated in the apex of the axilla, superior to the pectoralis minor muscle, and lies in close proximity to the **axillary vessels** [1]. - This location allows it to receive lymph from other axillary groups and drain into the supraclavicular lymph nodes.
Question 6: Cause of Farmer's lung -
- A. Sugarcane dust
- B. Cotton dust
- C. Grain dust (Correct Answer)
- D. Iron
Explanation: ***Grain dust*** - Farmer's lung is a form of **hypersensitivity pneumonitis** caused by inhaling dust from moldy hay or other agricultural products, primarily containing **thermophilic actinomycetes** found in stored grain. - Exposure to these organic dusts triggers an immune response in susceptible individuals, leading to inflammation of the **alveoli** and small airways. *Sugarcane dust* - Inhalation of sugarcane dust can lead to **bagassosis**, which is another type of **hypersensitivity pneumonitis** specific to sugarcane. - While also a form of occupational lung disease, it is distinct from farmer's lung, which specifically refers to moldy hay/grain exposure. *Cotton dust* - Exposure to cotton dust is primarily associated with **byssinosis**, a respiratory condition characterized by chest tightness and shortness of breath that worsens on the first day of the work week. - Byssinosis is believed to be caused by endotoxins and other substances in cotton dust, and it does not typically involve the immune-mediated alveolar inflammation seen in farmer's lung. *Iron* - Inhalation of iron particles can cause **siderosis**, a form of **pneumoconiosis** which is a benign condition with characteristic X-ray findings. - Siderosis is a type of mineral dust disease and does not involve the hypersensitivity reaction or the organic dust exposure characteristic of farmer's lung.
Question 7: What is the most common genetic factor associated with increased susceptibility to Neisseria infections?
- A. HLA-B27
- B. Complement deficiency (Correct Answer)
- C. IgA deficiency
- D. Factor H deficiency
Explanation: ***Complement deficiency*** - Deficiencies in the **terminal complement pathway (C5-C9)**, particularly C5b-C9 (membrane attack complex, MAC), significantly increase susceptibility to disseminated *Neisseria* infections. - The MAC is crucial for lysing Gram-negative bacteria like *Neisseria meningitidis* and *Neisseria gonorrhoeae*, and its absence allows for uncontrolled bacterial proliferation. *Factor H deficiency* - **Factor H** is a regulatory protein of the alternative complement pathway, preventing its overactivation on host cells. - Its deficiency typically leads to conditions like **atypical hemolytic uremic syndrome (aHUS)** and **dense deposit disease**, not primarily increased susceptibility to *Neisseria* infections. *HLA B27* - **HLA-B27** is a human leukocyte antigen strongly associated with a group of autoimmune inflammatory diseases called **spondyloarthropathies**, such as ankylosing spondylitis. - It does not directly impact the immune response to *Neisseria* infections or increase susceptibility to them. *IgA deficiency* - **Selective IgA deficiency** is the most common primary immunodeficiency, characterized by low or absent IgA levels. - Individuals with IgA deficiency are more prone to **recurrent respiratory and gastrointestinal infections**, but not specifically disseminated *Neisseria* infections.
Question 8: Ligamentum flavum consists of which fibres:
- A. Elastic (Correct Answer)
- B. Type-I collagen
- C. Reticular
- D. Type-II collagen
Explanation: The ligamentum flavum is predominantly composed of elastic fibers [1], which allow it to stretch and recoil during spinal movements. This high elastic content helps maintain the upright posture of the spine and prevents excessive flexion. Type I collagen is the most abundant collagen type, forming strong, inextensible fibers found in structures like tendons, ligaments, and bone, but is not the primary component of ligamentum flavum [1]. While present in some ligaments, its dominance would make the ligamentum flavum too stiff for its role in the spinal canal. Reticular fibers are fine, branching collagen fibers (primarily type III collagen) that form a supportive network in soft tissues and organs, but they are not a major component of the ligamentum flavum. Type II collagen is the primary collagen type found in hyaline cartilage and elastic cartilage, providing resistance to pressure. It is not a significant component of ligaments, especially those requiring high elasticity like the ligamentum flavum.
Question 9: Which of the following area is marked in the histology of lymph node? (AIIMS May 2017)
- A. Mantle zone
- B. Marginal zone
- C. Germinal center (Correct Answer)
- D. Paracortical area
Explanation: ***Germinal center*** - The image illustrates a **germinal center**, characterized by its **lighter staining** and a distinct network of cells (likely follicular dendritic cells) which are responsible for B-cell proliferation and differentiation. - The pointer indicates the surrounding, more basophilic lymphocytes, often seen adjacent to the paler germinal center. *Mantle zone* - The mantle zone surrounds the germinal center and consists of **small, inactive B-lymphocytes** that stain more densely (darker) than the cells within the germinal center. - It would be seen as a darker ring immediately outside the lighter germinal center. *Marginal zone* - The marginal zone is typically found in the **spleen** and is a region of B cells that surrounds the white pulp. - It is not a primary structural component identified within the follicular architecture of a lymph node in the manner depicted. *Paracortical area* - The paracortex is primarily a **T-cell zone**, located between the follicles and the medulla within the lymph node. - It would not exhibit the distinct follicular structure with a light center and surrounding darker cells as shown.
Question 10: The tonsils are derived from:
- A. 1st branchial pouch
- B. 2nd branchial pouch (Correct Answer)
- C. 3rd branchial pouch
- D. 4th branchial pouch
Explanation: The tonsils are derived from: ***Correct: 2nd branchial pouch*** - The **palatine tonsils** develop from the endodermal lining of the **second pharyngeal (branchial) pouch** - The pouch also forms the **supratonsillar fossa (tonsillar fossa)** - Mesenchymal tissue surrounding the pouch contributes to the lymphoid tissue of the tonsil *Incorrect: 1st branchial pouch* - Forms the **tympanic cavity**, **mastoid antrum**, and **eustachian tube (auditory tube)** - Not involved in tonsil development *Incorrect: 3rd branchial pouch* - Dorsal wing: forms the **inferior parathyroid glands** - Ventral wing: forms the **thymus** - These structures migrate caudally during development *Incorrect: 4th branchial pouch* - Dorsal wing: forms the **superior parathyroid glands** - Ventral wing: forms the **ultimobranchial body** (gives rise to parafollicular C cells of the thyroid) - Not involved in tonsil development
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