HIV affects: March 2005 and 2008, and September 2011
**Core Concept**
HIV (Human Immunodeficiency Virus) is a retrovirus that primarily targets and infects CD4+ T lymphocytes, also known as T helper cells, which play a crucial role in the immune system. This infection leads to a progressive decline in the number of CD4+ T cells, impairing the immune system's ability to fight off infections and diseases.
**Why the Correct Answer is Right**
HIV attaches to the CD4 receptors on the surface of CD4+ T cells, facilitating its entry into the cell. The virus then integrates its genetic material into the host cell's DNA, leading to the production of new viral particles. The depletion of CD4+ T cells compromises the immune system, making individuals susceptible to opportunistic infections and cancers. The hallmark of HIV infection is a low CD4+ T cell count, which is used to determine the stage of the disease.
**Why Each Wrong Option is Incorrect**
**Option A:** HIV also infects macrophages, but this is not the primary target of the virus.
**Option B:** HIV does not directly infect B cells, although it can affect their function indirectly.
**Option C:** While HIV can infect dendritic cells, this is not the primary mechanism of its pathogenesis.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that HIV's primary target is the CD4+ T cell, and a low CD4+ T cell count is a key indicator of HIV progression. This knowledge is crucial for diagnosing and managing HIV infection.
**Correct Answer:** C.