Inflammation and Repair Practice Questions

Q: Eosinophils are activated by which cytokine?

Interleukin-5 (IL-5). Interleukin-5 (IL-5) is the primary cytokine responsible for the recruitment, activation, and survival of eosinophils. It is produced mainly by T-helper 2 (Th2) cells and mast cells. IL-5 stimulates the production of eosinophils in the bone marrow and enhances their effector functions, such as degranulation and antibody-dependent cell-mediated cytotoxicity, making it a central mediator in allergic inflammation and parasitic infections. Analysis of Incorrect Options: * Interleukin-1 (IL-1): A pro-inflammatory cytokine produced by macrophages [1]. It primarily acts as an endogenous pyrogen (induces fever) and activates T-cells and neutrophils [1]. * Interleukin-4 (IL-4): This cytokine induces the differentiation of naive T-cells into Th2 cells and stimulates B-cell class switching to IgE [1]. While related to allergy, it does not directly activate eosinophils. * Interleukin-6 (IL-6): An acute-phase reactant mediator. It stimulates the liver to produce C-reactive protein (CRP) and promotes B-cell differentiation into plasma cells. High-Yield NEET-PG Pearls: * Mnemonic for Th2 Cytokines: "Hot T-Bone stEAk" (IL-1: Fever; IL-2: T-cells; IL-3: Bone marrow; IL-4: IgE; IL-5: IgA & Eosinophils). * Clinical Correlation: Mepolizumab and Reslizumab are monoclonal antibodies against IL-5 used in the treatment of severe eosinophilic asthma. * Eosinophilia: Defined as an absolute eosinophil count >500 cells/µL. Common causes include NAACP: Neoplasia, Asthma, Allergy, Collagen vascular diseases, and Parasites.

Q: Which of the following is NOT an example of a cellular adhesion molecule?

None of the above. ### Explanation The correct answer is **None of the above** because all three options listed (Integrins, Cadherins, and Selectins) are major families of **Cell Adhesion Molecules (CAMs)**. CAMs are transmembrane proteins that facilitate cell-to-cell or cell-to-extracellular matrix (ECM) interactions, which are vital for tissue integrity, signal transduction, and leukocyte trafficking. **Analysis of Options:** * **Integrins (Option A):** These are primarily involved in **cell-matrix** interactions. They link the intracellular cytoskeleton (actin) to ECM proteins like fibronectin and laminin. They play a crucial role in "inside-out" and "outside-in" signaling. * **Cadherins (Option B):** These are **calcium-dependent** glycoproteins responsible for **cell-cell** adhesion. They are the primary components of adherens junctions and desmosomes (e.g., E-cadherin in epithelial tissues). * **Selectins (Option C):** These are carbohydrate-binding lectins involved in the **initial rolling** phase of leukocyte extravasation. They mediate weak, transient interactions between leukocytes and vascular endothelium. **High-Yield NEET-PG Pearls:** 1. **Calcium Dependency:** Cadherins and Selectins are **Calcium-dependent**, whereas the Immunoglobulin (Ig) superfamily and most Integrins are not. 2. **Leukocyte Migration Sequence:** * **Rolling:** Mediated by **Selectins** (P and E-selectin). * **Tight Adhesion/Activation:** Mediated by **Integrins** (LFA-1, VLA-4) binding to ICAM-1/VCAM-1. * **Diapedesis:** Mediated by **PECAM-1** (CD31). 3. **Clinical Correlation:** A deficiency in Integrins (specifically CD18) leads to **Leukocyte Adhesion Deficiency (LAD) Type 1**, characterized by delayed umbilical cord separation and recurrent bacterial infections without pus formation.

Q: Which of the following is a chemokine?

IL-8. **Explanation:** **Correct Answer: B. IL-8** Chemokines are a specific subfamily of cytokines that act as chemoattractants to recruit inflammatory cells to the site of infection or injury. **Interleukin-8 (IL-8)**, also known as CXCL8, is the prototypical chemokine. It is primarily produced by macrophages and endothelial cells to induce **neutrophil chemotaxis** and activation. In the NEET-PG context, remember the mnemonic: *"Clean up on Aisle 8"* (IL-8 recruits neutrophils to clean up the site). **Analysis of Incorrect Options:** * **A. Leukotriene A4:** This is an intermediate in the arachidonic acid metabolism pathway. While its derivative, **LTB4**, is a potent neutrophil chemoattractant, LTA4 itself is an unstable precursor and not classified as a chemokine (which are protein signaling molecules). * **C & D. C5 and C3:** These are components of the complement system. While their cleavage products, **C5a** (and to a lesser extent C3a), are powerful "anaphylatoxins" and chemoattractants, they are plasma proteins/fragments, not cytokines or chemokines. **High-Yield Clinical Pearls for NEET-PG:** * **Potent Chemoattractants:** The "Big Four" frequently tested are **IL-8, LTB4, C5a, and Bacterial products (N-formyl methionine).** * **Chemokine Receptors:** CCR5 and CXCR4 are critical co-receptors for **HIV entry** into CD4+ T cells and macrophages. * **Classification:** Chemokines are classified into four groups based on the arrangement of cysteine residues: **CC, CXC, C, and CX3C.** IL-8 belongs to the **CXC** family.

Q: What substance is secreted by neutrophils?

Myeloperoxidase. ### Explanation **Correct Option: B. Myeloperoxidase** Neutrophils are the primary effectors of the innate immune system [1]. Their primary mechanism for killing pathogens is the **respiratory burst**. During this process, neutrophils produce **Myeloperoxidase (MPO)**, a heme-containing enzyme stored in their **primary (azurophilic) granules** [1]. MPO catalyzes the conversion of hydrogen peroxide ($H_2O_2$) and chloride ions ($Cl^-$) into **hypochlorous acid (HOCl)**—the active ingredient in household bleach—which is a potent bactericidal agent. **Analysis of Incorrect Options:** * **A. Superoxide dismutase (SOD):** This is an antioxidant enzyme that converts the superoxide radical ($O_2^-$) into $H_2O_2$. While present in neutrophils to manage oxidative stress, it is not a primary "secreted" effector molecule for pathogen destruction. * **C. Lysosomal enzymes:** While neutrophils contain lysosomes (granules) with various enzymes (like elastase or collagenase), "Lysosomal enzyme" is a generic category. **Myeloperoxidase** is the specific, hallmark enzyme secreted during the oxidative burst that defines neutrophil function in NEET-PG contexts. * **D. Catalase:** This enzyme breaks down $H_2O_2$ into water and oxygen. It is primarily used by aerobic bacteria (e.g., *Staphylococcus aureus*) to protect themselves against the neutrophil's oxidative burst, rather than being a primary secretion of the neutrophil itself. **NEET-PG Clinical Pearls:** * **MPO Deficiency:** The most common inherited defect of phagocytes; patients are usually asymptomatic except for a predisposition to *Candida* infections. * **Staining:** MPO staining is the gold standard for identifying **Acute Myeloid Leukemia (AML)** and differentiating it from ALL. * **Auer Rods:** These are clumps of azurophilic granules (containing MPO) found in leukemic blasts of AML.

Question 1

Eosinophils are activated by which cytokine?

Accepted Answer

Interleukin-5 (IL-5)

Answer

Interleukin-1 (IL-1)

Answer

Interleukin-4 (IL-4)

Answer

Interleukin-6 (IL-6)

Question 2

Which of the following is NOT an example of a cellular adhesion molecule?

Accepted Answer

None of the above

Answer

Integrin

Answer

Cadherin

Answer

Selectin

Question 3

Toll-like receptors recognize bacterial products and stimulate an immune response by:

Accepted Answer

Mediating transcription of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), which recruits cytokines.

Answer

Initiating perforin and granzyme-mediated apoptosis.

Answer

Triggering Fas-associated death domain (FADD) ligand-induced apoptosis.

Answer

Regulating cyclin activity.

Question 4

Which of the following is a chemokine?

Accepted Answer

IL-8

Answer

Leukotriene A4

Answer

C5

Answer

C3

Question 5

Which statement is true regarding Interleukin-1 (IL-1)?

Accepted Answer

Upregulates adhesion molecules

Answer

Mainly derived from neutrophils

Answer

Produces necrosis of tumor cells

Answer

Increases expression of MHC coded proteins

Question 6

Nearly 20% of the normal tensile strength of tissue at the site of a wound is gained after how much time of wound healing?

Accepted Answer

3 weeks

Answer

1 week

Answer

2 weeks

Answer

4 weeks

Question 7

What substance is secreted by neutrophils?

Accepted Answer

Myeloperoxidase

Answer

Superoxide dismutase

Answer

Lysosomal enzyme

Answer

Catalase

Question 8

What is the most important cytokine for the synthesis and deposition of connective tissue proteins?

Accepted Answer

TGF-β

Answer

PDGF

Answer

FGF-2

Answer

MMP

Question 9

All the statements related to neutrophil extracellular traps (NETs) are true except:

Accepted Answer

NETs provide a low concentration of antimicrobials at the site of infection.

Answer

NETs are an example of beneficial suicide for the neutrophil.

Answer

It is an extracellular fibrillary network.

Answer

NETs can be associated with an increased risk of autoimmune disease.

Question 10

Stem cells are located in which of the following locations in the body?

Accepted Answer

Intestine

Answer

Retina

Answer

Endometrium

Answer

Choana

Inflammation and Repair — MCQs

Inflammation and Repair — MCQs

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