## **Core Concept**
The question tests knowledge of immunophenotyping markers, specifically those associated with natural killer (NK) cells. CD16 and CD56 are significant markers in identifying and classifying immune cells.

## **Why the Correct Answer is Right**
NK cells are a type of lymphocyte that can kill tumor cells and virus-infected cells without prior sensitization. They are characterized by the presence of specific surface markers. **CD16 (FcγRIIIA)**, a low-affinity Fc receptor for IgG, and **CD56**, the neural cell adhesion molecule (NCAM), are commonly used to identify NK cells. Most NK cells are **CD56+** and **CD16+**, making these markers crucial for their identification.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately represent the cell type associated with CD16 and CD56.
- **Option B:** This option is incorrect as it does not correctly correspond with the markers mentioned.
- **Option C:** Some T cells can express CD56, but the combination of CD16 and CD56 is more specifically associated with NK cells, not T cells in general.
- **Option D:** This option might relate to other immune cells or contexts not directly associated with the specific markers CD16 and CD56.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **NK cells are CD56+ and CD16+**, which distinguishes them from other lymphocytes like T cells and B cells. This distinction is crucial in immunology and hematology for diagnosing and understanding diseases affecting the immune system.

## **Correct Answer:** .