| HIV infection Laboratory Tests for HIV Infection
Manifestations of HIV
Management of HIV infection
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In a healthy person, the
normal range of certain white blood cells called T4
lymphocyte cells (helper cells) is usually between 600
and 1200 (T4) cells per cubic millimeter (cells/mm3).
(The range depends on the test used.) When human
immunodeficiency virus (HIV) enters the bloodstream, it
primarily infects T4 cells. Asymptomatic individuals
infected with HIV usually have a lower than normal T4
cell count, and people with AIDS generally have between 0
and 500 T4 cells/mm3. The number of T8 lymphocyte cells
(suppressor cells) in an HIV-infected person usually
stays about the same. Because the number of T4 cells is
low, the total T-cell count is lower than normal, and the
T4/T8 cell ratio is lower than the usual 2 to 1 ratio. |
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HIV infection not only
reduces the number of T4 cells, it can also impair a T4
cell's functioning. HIV-infected individuals with very
low T4 cell counts tend to have more serious infections.
Therefore, regular immunologic tests to determine T4, T8,
and total T-cell counts can be an important element in
monitoring the health of an HIV-infected person. Two types of HIV have been identified to
date: HIV-1 and HIV-2. HIV-1 is the predominant HIV type
in the United States and throughout the world. HIV-2 is
primarily found in West Africa.
Origin of HIV
Virus
HIV-1 originated in non-human
primates, probably chimpanzees.
The origin of HIV-2 has been identified as being another
monkey species, the sooty mangabey (Cercocebus atys).
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