## **Core Concept**
Acute phase proteins are plasma proteins whose concentrations increase or decrease in response to inflammation or injury. These proteins are produced by the liver and play a crucial role in the body's defense mechanism. The acute phase response is a systemic reaction to severe infection, inflammation, or injury.

## **Why the Correct Answer is Right**
The correct answer, **C. Albumin, transthyretin**, represents negative acute phase proteins. Negative acute phase proteins are those whose plasma concentrations decrease in response to inflammation. **Albumin** is a major negative acute phase protein; its levels decrease during acute inflammation. **Transthyretin (prealbumin)** also decreases with inflammation, making it another negative acute phase protein.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it likely lists proteins that are either positive acute phase proteins or not directly related to the classification of acute phase proteins.
- **Option B:** This option is incorrect as it probably represents a mix of proteins that do not accurately reflect negative acute phase proteins.
- **Option D:** This option is incorrect because it does not accurately represent negative acute phase proteins.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that albumin levels can be used as a marker of nutritional status and inflammation. A decrease in albumin levels can indicate acute inflammation, chronic disease, or malnutrition. Remember, during acute phase response, **albumin levels decrease**, which can sometimes be misinterpreted as a sign of malnutrition.

## **Correct Answer:** . Albumin, transthyretin