**Core Concept**
Reed-Sternberg cells are a specific type of abnormal lymphocyte associated with Hodgkin lymphoma, a type of cancer that affects the immune system. These cells are characterized by their distinctive appearance under a microscope, with a large, irregular nucleus and abundant cytoplasm.

**Why the Correct Answer is Right**
Reed-Sternberg cells are the hallmark of Hodgkin lymphoma, particularly the classical subtype. They are thought to arise from germinal center B cells that have undergone malignant transformation. The presence of these cells is a key diagnostic criterion for Hodgkin lymphoma, and their identification is essential for distinguishing this disease from other types of lymphoma. The Reed-Sternberg cells express several specific markers, including CD30 and CD15, which can aid in their identification.

**Why Each Wrong Option is Incorrect**
**Option A:** Reed-Sternberg cells are not typically found in non-Hodgkin lymphoma, which is a broader category of lymphoid malignancies that do not share the same characteristic cells.
**Option B:** While Reed-Sternberg cells can be seen in the context of immune responses, they are not a normal component of the immune system and are instead indicative of a malignant process.
**Option C:** Reed-Sternberg cells are not associated with any specific viral infections, although some viruses have been implicated in the development of lymphoma.

**Clinical Pearl / High-Yield Fact**
Reed-Sternberg cells are typically found in the lymph nodes, spleen, and bone marrow of patients with Hodgkin lymphoma, and their presence is a key diagnostic criterion for this disease. The identification of these cells is essential for distinguishing Hodgkin lymphoma from other types of lymphoma and for guiding treatment decisions.

**Correct Answer:** D.