Which of the following toxins responsible for the symptoms of whooping cough acts indirectly to cause its effects?

• A. Pertussis toxin
• B. Tracheal cytotoxin
• C. Dermonecrotic toxin
• D. Adenylate cyclase toxin

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the question is asking which toxin associated with whooping cough causes symptoms indirectly, meaning it does not directly damage cells but instead triggers a cascade of effects leading to symptoms.
2. Step 2: Review the mechanism of each toxin listed: Pertussis toxin, Tracheal cytotoxin, Dermonecrotic toxin, and Adenylate cyclase toxin, focusing on how they cause damage or symptoms.
3. Step 3: Recall that Pertussis toxin acts by modifying host cell signaling pathways, particularly by ADP-ribosylation of G proteins, which disrupts immune responses and cellular communication, thus acting indirectly.
4. Step 4: Contrast this with Tracheal cytotoxin, which directly damages ciliated epithelial cells in the respiratory tract, causing direct cellular injury.
5. Step 5: Conclude that since Pertussis toxin causes symptoms through interference with host cell signaling rather than direct cytotoxicity, it is the toxin that acts indirectly to cause the effects of whooping cough.