CD4 Cell Count

CD4 cells are a subset of T lymphocytes (helper T cells), which are part of the body’s defense against fungal, viral, and parasitic infections and exhibit some control over neoplastic growth.
The normal CD4 cell count range is approximately 500 – 1500 cells/mm³.
A drop in CD4 cell count indicates immune system deterioration.
A CD4 cell count below 200 cells/mm³ is considered severe immune suppression.
When the CD4 cell count drops below 200 cells/mm³, a patient will start to receive prophylaxis against certain opportunistic infections, such as Pneumocystis jerovecil pneumonia, formerly called Pneumocystis carinii pneumonia (PCP).
A CD4 cell count below 200 cells/mm³ is a definition of AIDS.
The development of oral lesions is associated with a decreased CD4 cell count.

HIV infection stage, based on age-specific CD+ T-lymphocyte count or CD4+ T-lymphopcyte percentage of total lymphocyte count#

Age on date of CD4 T-lymphocyte test
	<1 year		1-5 years		6 years through adult
Stage	Cells/µL	%	Cells/µL	%	Cells/µL	%
1	≥1,500	≥34	≥1,000	≥30	≥500	≥26
2	750-1,499	26-33	500-999	22-29	200-499	14-25
3	<750	<26	<500	<22	<200	<14
The stage is based primarily on the CD4+ T-lymphocyte count; the CD4+ T-lymphocyte count takes precedence over the CD4 T-lymphocyte percentage, and the percentage is considered only if the count is missing.