Question

Male not responding to O₂, diagnosis ARDS. What is the role of IL-8 in ARDS?

• A. Endothelial cell activation
• B. Requirement of neutrophil
• C. Macrophage activation
• D. Promote surfactant production

Hint:

IL-8 (CXCL8) is the classic chemokine that calls in one specific leukocyte — think which cell does the alveolar damage in ARDS.

Answer 1

The Correct Option is B

Step 1: Understand ARDS pathophysiology. Acute Respiratory Distress Syndrome (ARDS) is diffuse alveolar damage caused by an exaggerated inflammatory response. The hallmark is injury to the alveolar-capillary membrane leading to protein-rich exudative pulmonary edema, hypoxemia refractory to supplemental oxygen, and bilateral infiltrates. The central effector cell of this injury is the neutrophil.

Step 2: Identify what IL-8 (CXCL8) does. Interleukin-8 is a chemokine secreted by alveolar macrophages and epithelial cells. Its principal action is to act as a potent chemoattractant that recruits and activates neutrophils, drawing them from the circulation into the alveolar space. The recruited neutrophils then release reactive oxygen species, proteases (elastase) and pro-inflammatory mediators that damage the alveolar-capillary barrier. High BAL fluid IL-8 levels in ARDS correlate with neutrophil influx and worse prognosis.

Step 3: Match to the option. Because IL-8's defining role is neutrophil chemotaxis/recruitment, the answer relating IL-8 to the "requirement of neutrophil" (i.e., it is required for neutrophil recruitment) is correct - Option B.

Step 4: Why the other options are wrong. (A) Endothelial cell activation is driven mainly by TNF-α and IL-1, not IL-8. (C) Macrophage activation is mediated by IFN-γ and other signals; macrophages are the source of IL-8, not its target. (D) Surfactant production is a function of type II pneumocytes and is actually impaired in ARDS - IL-8 does not promote it.

Final Answer: Option B - Requirement of neutrophil (neutrophil recruitment/chemotaxis).