YOU ARE HERE:
CD4 cell counts
CD4 cells, sometimes also called T-cells, or T-helper cells, are white blood cells which organise the immune system’s response to bacterial, fungal and viral infections.
CD4 cell counts in people without HIV
A normal CD4 cell count in an HIV-negative man is between 400 and 1600 per cubic millimetre of blood. CD4 cell counts in HIV-negative women tend to be a little higher, between 500 – 1600.
Even if you don’t have HIV, many factors can affect your CD4 cell count. For example it’s known that:
- Women have higher CD4 cell counts than men (by about 100).
- Women’s CD4 cell counts go up and down during the menstrual cycle.
- Oral contraceptives can lower a woman’s CD4 cell count.
- Smokers tend to have higher CD4 cell counts (by about 140).
- CD4 cell counts fall after rest – by as much as 40%.
- A good night’s sleep can mean that you have a lower CD4 cell count the following morning, but a higher CD4 cell count the next afternoon.
None of these factors seems to make any difference to how able your immune system is to fight infections.
Only a small portion of your body's CD4 cells are in the blood. The rest are in the lymph nodes and tissue, and the fluctuations noted above might be due to the movement of CD4 cells between blood and tissue.
CD4 cell counts in people with HIV
Soon after infection with HIV, your CD4 cell count probably dropped sharply, before stabilising at around 500 – 600. It seems that people who experience a greater initial drop in CD4 cell count and a lower stabilisation in their CD4 cell count may be at risk of faster disease progression. Even while you are well and have no obvious symptoms of HIV, millions of CD4 cells are infected by HIV and lost every day, and millions more are produced to replace them.
It’s estimated, however, that without treatment, an HIV-positive person’s CD4 cell count drops by about 45 cells every six months, with greater falls experienced by people with higher CD4 cell counts.
A CD4 cell count between 200 and 500 indicates that some damage to your immune system has occurred.
Steeper falls in CD4 cell counts are experienced in the year before AIDS develops, which is why you are recommended to have your CD4 cell count regularly monitored once it goes below 350.
Looking at your CD4 cell count can also provide a guide for decisions about your need to take medicines to prevent some AIDS-defining illnesses. For example, if your CD4 cell count is below 200, you are recommended to take antibiotics to prevent you getting PCP pneumonia.
Your CD4 cell count can naturally fluctuate, so don’t put too much emphasis on a single test result. Rather, look at the trend in a number of recent CD4 cell counts.
If your CD4 cell count is high, you have no symptoms, and are not taking anti-HIV medication, then it probably only needs monitoring every few months or so.
However, if it’s falling rapidly, you are unwell, are taking part in a clinical trial, or are taking anti-HIV drugs, then it should be monitored more often.
CD4 cell percentages
Sometimes, as well as counting the number of CD4 cells, doctors will also assess what percentage of all your white blood cells are CD4 cells. This is called the CD4 cell percentage. A normal result in a person with an intact immune system is about 40%, and a CD4 cell percentage below 20% indicates the same risk of becoming ill with an AIDS-defining illness as a CD4 cell count of about 200.
CD4 cell counts and HIV treatment
Your CD4 cell count can be used to help decide when you need to start anti-HIV treatment, and as an indication of how successful these treatments are.
Once your CD4 cell falls to about 350, your doctor should start talking to you about whether you need to start taking anti-HIV treatments.
If your CD4 cell count falls to between 200 and 250 cells, you are recommended to start anti-HIV treatment. A CD4 cell count of this level indicates that you are at a real risk of becoming ill with an AIDS-defining illness.
It also seems that if you wait until your CD4 cell count falls to below 200, you are less likely to respond well to anti-HIV treatment. However, there doesn’t seem to be any health benefit from starting HIV treatment if your CD4 cell count is above 350.
Once you start anti-HIV treatment, your CD4 cell count should start to slowly increase. If you experience a fall in your CD4 cell count over a number of tests, this should alert your doctor that there’s something wrong with your HIV treatments.