Inflammation and Repair Practice Questions

Q: Which of the following complement components is chemotactic?

C5a. The complement system is a crucial part of the innate immune response, involving a cascade of proteins that lead to pathogen clearance [1]. The correct answer is **C5a** because it is the most potent **chemoattractant** (chemotactic factor) of the complement system. * **C5a (Correct):** Known as a "complete" anaphylatoxin, C5a functions as a powerful chemotactic agent for neutrophils, monocytes, eosinophils, and basophils. It recruits these inflammatory cells to the site of infection and also increases vascular permeability. * **C3a (Incorrect):** While C3a is an **anaphylatoxin** (triggers histamine release from mast cells), it has negligible chemotactic activity compared to C5a. Its primary role is inducing local inflammation and vasodilation. * **C3b (Incorrect):** C3b acts primarily as an **opsonin**. It coats the surface of pathogens, making them "tasty" for phagocytes (macrophages and neutrophils) which possess C3b receptors. It also helps in the formation of C5 convertase. **High-Yield Clinical Pearls for NEET-PG:** 1. **Potency Order:** For chemotaxis, C5a is significantly more potent than C3a. 2. **Opsonization:** Remember the mnemonic **"C3b binds bacteria"** (Opsonization). 3. **Anaphylatoxins:** C3a, C4a, and C5a (in increasing order of potency: C4a < C3a < C5a). 4. **Membrane Attack Complex (MAC):** Formed by C5b-C9; essential for lysing Gram-negative bacteria like *Neisseria*. 5. **Deficiency:** C3 deficiency is the most severe as it is the central point of all three pathways, leading to recurrent pyogenic infections.

Q: Which interleukin is primarily produced by macrophages?

IL-1. **Explanation:** **Interleukin-1 (IL-1)** is a key pro-inflammatory cytokine primarily produced by **activated macrophages** and monocytes. It plays a central role in the innate immune response by acting as an endogenous pyrogen (inducing fever via the hypothalamus), stimulating T-cell activation, and promoting the synthesis of acute-phase reactants by the liver. **Analysis of Options:** * **IL-1 (Correct):** Produced by macrophages. It mediates inflammation and induces the expression of adhesion molecules on endothelial cells. * **IL-2:** Produced primarily by **Th1 cells** (T-lymphocytes). It acts as a T-cell growth factor, stimulating the proliferation of T and B cells. * **IL-3:** Produced by **activated T-cells**. It functions as a colony-stimulating factor, supporting the growth and differentiation of hematopoietic stem cells in the bone marrow. * **IL-4:** Produced by **Th2 cells** and mast cells. It promotes B-cell differentiation into plasma cells and induces "class switching" to **IgE** and IgG4. **High-Yield NEET-PG Pearls:** * **Hot T-Bone Steak** (Mnemonic for IL 1-5): * **IL-1:** **Hot** (Fever/Pyrogen). * **IL-2:** Stimulates **T**-cells. * **IL-3:** Stimulates **Bone** marrow. * **IL-4:** Stimulates Ig**E** production. * **IL-5:** Stimulates Ig**A** production and Eosinophils. * **IL-6** is also a major product of macrophages and is the primary inducer of **CRP (C-Reactive Protein)**. * **IL-8** is the chief chemotactic factor for **Neutrophils** ("Clean up on aisle 8").

Q: Vascular dilation in the inflammatory response is mediated by all the following EXCEPT?

Leukotrienes. **Explanation:** The inflammatory response involves a complex interplay of chemical mediators that regulate vascular changes [1]. The correct answer is **Leukotrienes** (specifically $LTC_4$, $LTD_4$, and $LTE_4$) because their primary vascular effect is **vasoconstriction** and increased vascular permeability (venular gaps), rather than vasodilation [2]. **Analysis of Options:** * **Leukotrienes (Correct):** While $LTB_4$ is a potent chemotactic agent, the cysteinyl leukotrienes ($LTC_4, D_4, E_4$) cause intense vasoconstriction and bronchospasm [2]. They do not mediate vasodilation [1]. * **Prostaglandins (Incorrect):** Prostaglandins, specifically $PGI_2$ (Prostacyclin), $PGE_1$, $PGE_2$, and $PGD_2$, are the principal mediators of **vasodilation** during inflammation [2]. They also potentiate the edema-forming effects of other mediators. * **C3a and C5a (Incorrect):** Known as **anaphylatoxins**, these complement fragments trigger mast cell degranulation [1]. This releases **Histamine**, which is the most well-known mediator of early vasodilation and increased capillary permeability. Therefore, they indirectly mediate vascular dilation. **High-Yield Clinical Pearls for NEET-PG:** * **Vasodilation Mediators:** Histamine, Prostaglandins ($PGI_2, PGE_2$), Nitric Oxide (NO), and Bradykinin [1]. * **Increased Permeability Mediators:** Histamine, Bradykinin, Leukotrienes ($LTC_4, D_4, E_4$), and Substance P [2]. * **Chemotaxis Mediators:** $LTB_4$, $C5a$, IL-8, and Bacterial products (N-formyl methionine) [1]. * **Pain Mediators:** Prostaglandins ($PGE_2$) and Bradykinin [1]. * **Fever Mediators:** $IL-1$, $TNF$, and Prostaglandins [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 100-101. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 95-96.

Q: Which of the following is NOT a receptor for integrins?

Platelet-derived growth factor. **Explanation:** **Integrins** are transmembrane heterodimeric proteins (composed of $\alpha$ and $\beta$ subunits) that function as primary receptors for the **Extracellular Matrix (ECM)** and cell-cell adhesion. **Why Option D is Correct:** **Platelet-derived growth factor (PDGF)** is a soluble cytokine/growth factor, not an adhesion molecule. It binds to specific **Receptor Tyrosine Kinases (RTKs)**, not integrins. While PDGF signaling can influence integrin activity (crosstalk), it does not serve as a ligand or receptor for integrins. **Analysis of Incorrect Options:** * **A. Fibronectin:** This is a major ECM protein. Integrins (specifically $\alpha_5\beta_1$) act as the primary receptors for fibronectin via the **RGD (Arg-Gly-Asp)** sequence. * **B. Glycoprotein on platelet surface:** The most famous integrin is **GPIIb/IIIa** ($\alpha_{IIb}\beta_3$), found on platelets. It binds fibrinogen and von Willebrand factor to facilitate platelet aggregation. * **C. Leukocyte adhesion molecule:** Integrins like **LFA-1** ($\alpha_L\beta_2$) and **VLA-4** ($\alpha_4\beta_1$) are expressed on leukocytes. They bind to ligands like ICAM-1 and VCAM-1 on endothelial cells, crucial for leukocyte extravasation. **High-Yield Clinical Pearls for NEET-PG:** 1. **Glanzmann Thrombasthenia:** A bleeding disorder caused by a deficiency or defect in the integrin **GPIIb/IIIa**. 2. **Leukocyte Adhesion Deficiency (LAD) Type 1:** Caused by a defect in the **$\beta_2$ subunit (CD18)** of integrins, leading to impaired neutrophil migration and delayed umbilical cord separation. 3. **RGD Sequence:** Many integrins recognize the Arginine-Glycine-Aspartate (RGD) tripeptide sequence in their ligands (e.g., fibronectin, vitronectin).

Question 1

A 5-year-old boy punctures his thumb with a rusty nail. Four hours later, the thumb appears red and swollen. Which of the following serum proteins activates the complement, coagulation, and fibrinolytic systems at the site of injury?

Accepted Answer

Hageman factor

Answer

Bradykinin

Answer

Kallikrein

Answer

Plasmin

Question 2

Which of the following complement components is chemotactic?

Accepted Answer

C5a

Answer

C3a

Answer

Both

Answer

C3b

Question 3

Which interleukin is primarily produced by macrophages?

Accepted Answer

IL-1

Answer

IL-2

Answer

IL-3

Answer

IL-4

Question 4

An 8-year-old girl with asthma presents with respiratory distress, a history of allergies and upper respiratory tract infections, and wheezing associated with exercise. Which of the following preformed substances, released from mast cells and platelets, results in increased vascular permeability in the lungs?

Accepted Answer

Histamine

Answer

Bradykinin

Answer

Hageman factor

Answer

Leukotrienes (SRS-A)

Question 5

Which of the following is activated by the binding of chemotactic agents to leukocyte membrane receptors?

Accepted Answer

Phospholipase C

Answer

Leukotriene B4

Answer

Histamine

Answer

Tumor necrosis factor

Question 6

Macrophages are converted to epithelioid cells by which cytokine?

Accepted Answer

IFN-γ

Answer

IL-2

Answer

TNF-α

Answer

TGF-β

Question 7

Which of the following is an opsonin?

Accepted Answer

C3b

Answer

C3a

Answer

C4a

Answer

C5a

Question 8

Vascular dilation in the inflammatory response is mediated by all the following EXCEPT?

Accepted Answer

Leukotrienes

Answer

Prostaglandins

Answer

C3a

Answer

C5a

Question 9

Which of the following is NOT a receptor for integrins?

Accepted Answer

Platelet-derived growth factor

Answer

Fibronectin

Answer

Glycoprotein on platelet surface

Answer

Leukocyte adhesion molecule

Question 10

A 25-year-old woman presents with a 2-week history of febrile illness and chest pain. She has an erythematous, macular facial rash and tender joints, particularly in her left wrist and elbow. A CBC shows mild anemia and thrombocytopenia. She is noted to have increased serum levels of ceruloplasmin, fibrinogen, 
2-macroglobulin, serum amyloid A protein, and C-reactive protein. Together, these markers belong to which of the following families of proteins?

Accepted Answer

Acute phase proteins

Answer

Anaphylatoxins

Answer

Inhibitors of platelet activation

Answer

Regulators of coagulation

Inflammation and Repair — MCQs

Inflammation and Repair — MCQs

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