**Core Concept:** The question is asking about the most specific anatomic changes observed in HIV (Human Immunodeficiency Virus) infection. HIV primarily targets the immune system, particularly CD4+ T-cells, leading to immunodeficiency.

**Why the Correct Answer is Right:** The correct answer, **C. Lymph Node:** HIV primarily affects the lymphatic system due to its dependence on CD4+ T-cells. Lymph nodes are crucial in the immune response, and HIV targets these cells, causing them to become enlarged (lymphadenopathy). This enlargement is often the first clinical sign of HIV infection, as it is specific to HIV and not seen in other conditions.

**Why Each Wrong Option is Incorrect:**

A. **HIV-Induced Immunodeficiency:** While this is a correct concept, it does not specifically focus on anatomic changes.
B. **Central Nervous System Involvement:** HIV does affect the central nervous system, but the changes are not as specific as those seen in the lymph nodes.
D. **Lymphopenia:** This is a decrease in lymphocytes, a broader concept related to HIV infection but not specific to anatomic changes in the body.

**Clinical Pearl:** The most specific anatomic change in HIV infection is the enlargement of lymph nodes, which is a crucial early marker for HIV infection and can guide clinicians to initiate appropriate management and counselling for the patient.