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Considerable variation exists in the relative risk of death following different AIDS defining clinical conditions. According to the US CDC definition, one has AIDS if he/she is infected with HIV and present with one of the following: A CD4+ T-cell count below 200 cells/μl (or a CD4+ T-cell percentage of total lymphocytes of less than 14%) OR
Declining CD4 T-cell counts are considered to be a marker of progression of HIV infection. A normal CD4 count can range from 500 cells/mm3 to 1000 cells/mm3. In HIV-positive people, AIDS is officially diagnosed when the count drops below 200 cells/μL or when certain opportunistic infections occur. This use of a CD4 count as an AIDS criterion ...
The results of a viral load test help determine when a CD4 count is indicated. [1] CD4 cells are the primary target of HIV. A CD4 test quantifies Helper T cells and is often combined with viral load testing to monitor the progression of HIV. CD4 testing shows the strength of the immune system, but does not report viral activity.
The latency stage involves few or no symptoms and can last anywhere from two weeks to twenty years or more, depending on the individual. AIDS, the final stage of HIV infection, is defined by low CD4+ T cell counts (fewer than 200 per μL), various opportunistic infections, cancers, and other conditions.
In 1993, the CDC added pulmonary tuberculosis, recurrent pneumonia and invasive cervical cancer [2] to the list of clinical conditions in the AIDS surveillance case definition published in 1987 [3] and expanded the AIDS surveillance case definition to include all HIV-infected persons with CD4+ T-lymphocyte counts of fewer than 200 cells/μL or ...
The CD8 + T cell response is thought to be important in controlling virus levels, which peak and then decline, as the CD4 + T cell counts recover. A good CD8 + T cell response has been linked to slower disease progression and a better prognosis, though it does not eliminate the virus. [102] Ultimately, HIV causes AIDS by depleting CD4 + T cells.
HIV can infect a variety of immune cells such as CD4 + T cells, macrophages, and microglial cells. HIV-1 entry to macrophages and CD4 + T cells is mediated through interaction of the virion envelope glycoproteins (gp120) with the CD4 molecule on the target cells' membrane and also with chemokine co-receptors. [25] [43]
In the AIDS phase, the CD4 T-cell count significantly drops to below 200 cells per cubic millimeter. Individuals with AIDS become immunocompromised due to irreversible damage to the immune system and lymph nodes. The immune system does not have the ability to generate new T cells.