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 infection are instead used by HIV to reproduce.

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 try to fight HIV. These are called HIV-specific CD4 cells (or T4 cells). However, these cells get worn out and usually disappear within 6 months.

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

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

Active cells with HIV die more quickly than CD4 cells in someone who is HIV negative. They live for 1-2 days instead of 3-4 days. 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 have HIV.

ART blocks HIV from reproducing. This 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 2021.