A 40-year-old male, who was in good health earlier, begins experiencing a chronic cough. Over the following 6 weeks, the cough gradually worsens and becomes productive. He is also coughing up blood, and notes weight loss, fever, and night sweats. A sputum sample is positive for acid-fast bacilli. Which of the following pathogenic mechanisms can be primarily attributed to the etiologic agent involved in this disease?
Correct Answer: Cell-mediated hypersensitivity
Description: Most cases of tuberculosis are caused when patients inhale droplet nuclei containing infectious organisms. While the bacilli are deposited on the alveolar spaces, they do not clog up the alveoli but are engulfed by macrophages. Tissue injury is not a result of toxin secretion but of cell-mediated hypersensitivity; that is, "immunologic injury." Humoral (antibodies) immunity would not be responsible for tissue damage since CMI is reacting against the organism. Adhesion sites are not implicated as virulence factors and toxins apparently are not made by the organisms.
Category:
Microbiology
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