These cells help defend the body against infection by directing other “killer” cells to neutralize foreign agents.
This is when a person is said to beimmunocompromised.
What Are CD4 Helper T Cells?
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T cells are a subset of lymphocytes that play different roles in the immune system.
They are called T cells because they mature in thethymus glandafter being produced by thebone marrow.
Their counterpart, calledB cells, are also produced in the bone marrow but mature in the spleen.
During maturation, certain T cells will develop a protein on their surface called CD4.
Types of CD4 T Cells
There are several types of CD4 T cells that serve different functions.
They are commonly divided into conventional T helper (Th) cells and regulatory T (Treg) cells.
For example, interleukin 17 produced by Th17 can damage healthy cells if produced in excess.
Treg cells prevent this from happening.
These are called memory CD4 T cells.
Role of CD4 T Cells in HIV Infection
CD4 T cells help fight HIV.
Ironically, they are the same cells that HIV targets for infection.
But they don’t fully reset the infection.
This effectively “reprograms” the infected cell, turning it into an HIV-producing factory.
After producing thousands of new viruses, the infected cell eventually dies.
These so-calledopportunistic infectionsare what account for the majority of illnesses in people with advanced HIV.
Does Everyone With HIV Get AIDS?
With rare exceptions, anyone with HIV who remains untreated will get AIDS.
If treated withantiretroviral drugs, a person can today expect to live a normal to near-normal life expectancy.
This is done with a simple blood test called aCD4 count.
The CD4 counts measure the number of CD4 T cells in a cubic millimeter of blood (cells/mm3).
In most healthy people, the CD4 count is between 500 and 1,500 cells/mm3.
Can Your CD4 Count Return to Normal?
This is more difficult if treatment is delayed.
These problems have been largely overcome.
Today, treatment of HIV starts immediately upon diagnosis.
Where it does play a part is in the initiation ofprophylactic drugsused to prevent opportunistic infections.
It can help fight many infections but is ironically the target of HIV infection.
As HIV progressively depletes these cells, the body becomes less able to defend itself against otherwise harmless infections.
With early treatment, a person with HIV may return to a normal CD4 count of 500 or above.
If left untreated, HIV will almost invariably progress to AIDS.
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