HIV mainly infects:

Concept:

HIV (Human Immunodeficiency Virus) is a retrovirus whose envelope glycoprotein (gp120) binds specifically to the CD4 receptor. CD4 receptors are expressed predominantly on Helper T-lymphocytes (also called T4 or CD4+ T-cells), which makes these cells HIV's principal point of entry.

Application:

Once HIV binds to and enters a Helper lymphocyte, it uses the cell's own machinery to replicate, progressively destroying the infected Helper T-cell population. Because Helper T-cells normally coordinate the rest of the immune response — activating B-cells to produce antibodies and stimulating cytotoxic T-cells — their depletion cripples the body's ability to fight infections, producing the immunodeficiency that defines AIDS (Acquired Immunodeficiency Syndrome).

Cross-check:

• Cytotoxic T-lymphocytes are effector cells that destroy already-infected cells; they respond to infection rather than being HIV's main target.

• Killer lymphocytes (Natural Killer cells) act through innate, non-specific immune surveillance and are not the lineage HIV specifically depletes.

• ‘Cell-mediated T-lymphocytes’ is not a distinct cell type — cell-mediated immunity is a broad mechanism carried out collectively by several T-cell subsets, so it cannot name a specific host cell.

So, HIV mainly infects Helper lymphocytes.