Treatment training manual

1. 6 How HIV interacts with the immune system

HIV is especially difficult for the body to deal with. This is because the cells that the body uses to fight a viral infection are instead used by HIV to reporduce and replicate.

These two factors are like a dog chasing its tail.

  • HIV makes the body produce more CD4 cells to fight this new virus.
  • These new cells provide more target cells for HIV to infect and reproduce.
  • The body responds by making even more cells to fight the new virus.

Most people develop immune cells that specifically try to fight the virus. These are called HIV-specific CD4 cells (or T4 cells). However, these cells get worn out and disappear in most people within 6 months after infection.

HIV then continues infecting other CD4 cells. Without treatment, usually over many years, the rest of the immune system is worn down.

This details of the immune response are very complicated. The main point is that HIV makes the immune system become overactive, producing more and more cells. Over time the immune system loses out. This is why without HIV treatment (ART) your CD4 count drops over time.

Active cells with HIV die more quickly than T cells in someone who is HIV negative: after 1-2 days instead of 3-4 days. HIV infected cells also signal to uninfected cells to die more quickly. Therefore, HIV doesn’t need to infect every cell to cause them to die. Only 1 in 1000 CD4 cells are likely to be infected with HIV.

ART blocks HIV from reproducing, and returns your immune system back to an almost normal state.

HIV and the immune system before ART

HIV and the immune system before ARV treatment

HIV and the immune system after ART

HIV and the immune system after ARV treatment

Last updated: 1 January 2016.