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Why does the loss of helper T cells weaken the immune system in AIDS?

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Diagram illustrating the process of retrovirus infection and reverse transcription, showing a retrovirus entering a host cell, releasing viral RNA, reverse transcriptase converting RNA to DNA, integration into the host genome, transcription of new viral RNA, assembly of new virions, and budding from the cell. — Reverse transcriptase After a retrovirus infects a cell, an enzyme known as reverse transcriptase converts viral RNA into proviral DNA in the cytoplasm. Proviral DNA then enters the nucleus, where it is incorporated into the host cell's DNA.

Helper T cells, also known as CD4+ T cells, are essential mediators of the immune system because they produce factors that activate nearly all other immune cells, including B cells that produce antibodies, cytotoxic T cells that kill infected cells, and macrophages that attack pathogens.12

In AIDS, the human immunodeficiency virus (HIV) specifically targets these cells by binding to the CD4 protein on their surface. Once inside, the virus uses the enzyme reverse transcriptase to convert its RNA genome into DNA, which is then integrated into the host cell's genome. This process hijacks the cell to produce new viral particles, ultimately leading to the death of the infected helper T cell.23

Because the body cannot produce new helper T cells fast enough to replace those destroyed by the virus, the overall population of these cells declines. The loss of these central coordinators cripples the immune system's ability to recognize and fight off infections, leaving the body vulnerable to diseases it would otherwise be able to combat.21