What are CD 4 Cells
And Why Do We Measure Them?
Our blood is made up of two components: liquid and solid.
The liquid part of the blood is called plasma. The solid part is made up of cells.
There are essentially three types of cells in the blood:
- Red blood cells (RBC) - bring oxygen to our tissues.
- Platelets - help the blood clot, the stop bleeding
- White blood cells (WBC) - identify, attack, and destroy
infection and cancerous cells. CD4 cells are a special type of white blood cells.
The cells have a receptor on the outside that allows HIV to bind with the CD4 cell and inject its genetic code.
Think of a lock with a key:
HIV then uses the machinery of the CD4 cell to make more HIV which ends up destroying the CD4 cell.
The CD4 count is a test which measures the number of CD4 cells in a blood sample. Normal CD4 counts in adults range from 600-1500 cells.
This number is a laboratory marker of the strength of a person's immune system.
It helps to determine how advanced HIV disease has become.
One of the criteria for an AIDS diagnosis is when the CD4 count drops below 200 cells. At this point there is a great risk for developing opportunistic infections like pneumocystis carinii pneumonia (PCP).
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