Which cell type does HIV primarily invade?

HIV primarily invades CD4 cells, which are a type of T lymphocyte, also referred to as helper T cells. These cells play a crucial role in the immune system by orchestrating the immune response, helping to activate other immune cells like B cells and cytotoxic T cells. The virus specifically targets the CD4 receptor on these cells, using it to gain entry into the cell. Once inside, HIV can replicate and ultimately lead to the destruction of these crucial immune cells, resulting in immunodeficiency.

This invasion of CD4 cells is fundamental to understanding how HIV affects the immune system and ultimately leads to conditions such as AIDS, where the body's ability to fend off infections is severely compromised. Other cell types listed in the options, such as B cells, neutrophils, and platelets, do not serve as the primary targets for HIV. While they play significant roles in the immune response and hemostasis, they do not have the same compatible receptors that HIV uses to enter and infect host cells. This makes CD4 cells the focal point in the context of HIV infection.