## **Core Concept**
The human immunodeficiency virus (HIV) targets and selectively infects specific immune cells, leading to their destruction. This results in the progressive weakening of the immune system. The primary cells affected are those expressing the CD4 antigen.

## **Why the Correct Answer is Right**
HIV selectively infects and destroys **CD4+ T lymphocytes** (also known as T helper cells). This is because HIV uses the CD4 molecule as its primary receptor to gain entry into these cells. Once inside, the virus replicates and destroys the host cells, leading to a decline in their numbers. This destruction is central to the immunopathogenesis of HIV infection and the development of acquired immunodeficiency syndrome (AIDS).

## **Why Each Wrong Option is Incorrect**
- **Option A:** B cells are not the primary target of HIV infection. While B cells can be indirectly affected by HIV through dysfunctional immune activation and the production of aberrant antibodies, they are not directly destroyed by HIV.
- **Option B:** Neutrophils are not targeted by HIV. They are a type of granulocyte and play a crucial role in the innate immune response, particularly against bacterial infections.
- **Option C:** Macrophages can be infected by HIV, but they are not the cells whose destruction is most closely associated with the progression to AIDS. Macrophages can serve as reservoirs for HIV.
- **Option D:** This option is not provided, but based on the correct answer, we know that the focus is on CD4+ T lymphocytes.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the depletion of **CD4+ T lymphocytes** is a hallmark of HIV infection and AIDS. Monitoring CD4+ T cell counts is crucial for assessing the progression of the disease and the effectiveness of antiretroviral therapy (ART).

## **Correct Answer:** C. CD4+ T lymphocytes.