A 26-year-old man has had myalgias and a fever for the past week. On physical examination, his temperature is 38.6deg C. He has diffuse muscle tenderness, but no rashes or joint pain on movement. Laboratory studies show elevated serum creatine kinase and peripheral blood eosinophilia. Larvae of Trichinella spiralis are present within the skeletal muscle fibers of a gastrocnemius biopsy specimen. Two years later, a chest radiograph shows only a few small calcifications in the diaphragm. Which of the following immunologic mechanisms most likely contributed to the destruction of the larvae?

**Core Concept**
Trichinosis is a parasitic infection caused by Trichinella spiralis, typically acquired through the ingestion of undercooked pork. The larvae of the parasite invade the skeletal muscle fibers, leading to muscle pain, fever, and eosinophilia.

**Why the Correct Answer is Right**
The correct answer is related to the host's immune response to the parasite. In this case, the destruction of the larvae is primarily mediated by the eosinophils, a type of white blood cell that plays a key role in combating parasitic infections. Eosinophils release granules that contain enzymes, such as eosinophil peroxidase, which help to kill the parasites. The elevated serum creatine kinase and peripheral blood eosinophilia in this patient's laboratory studies support this mechanism. Additionally, the presence of larvae in the skeletal muscle fibers and the subsequent calcification of the diaphragm are indicative of the host's immune response to the parasite.

**Why Each Wrong Option is Incorrect**
**Option A:** Complement system activation is not the primary mechanism of parasite destruction in this case. While the complement system can contribute to the elimination of pathogens, it is not the main mechanism involved in the destruction of Trichinella spiralis larvae.

**Option B:** Antibody-mediated immunity is not the primary mechanism of parasite destruction in this case. Although antibodies can play a role in combating parasitic infections, the destruction of Trichinella spiralis larvae is primarily mediated by eosinophils.

**Option C:** Cell-mediated immunity is not the primary mechanism of parasite destruction in this case. While T cells can contribute to the elimination of pathogens, the destruction of Trichinella spiralis larvae is primarily mediated by eosinophils.

**Option D:** None of the above is incorrect because the correct answer is a type of cell-mediated immunity.

**Clinical Pearl / High-Yield Fact**
Trichinosis is a parasitic infection that can lead to significant morbidity and mortality if left untreated. The presence of larvae in the skeletal muscle fibers and the subsequent calcification of the diaphragm are classic signs of the infection. Early diagnosis and treatment with anthelmintic medications can help to alleviate symptoms and prevent complications.

**Correct Answer:** D.

✓ Correct Answer: B. Antibody-mediated cellular cytotoxicity (ADCC)