Table of ContentsView AllTable of ContentsFunctionTypesRole in HIV InfectionRole in HIV DiagnosisRole in HIV Treatment
Table of ContentsView All
View All
Table of Contents
Function
Types
Role in HIV Infection
Role in HIV Diagnosis
Role in HIV Treatment
Without CD4 T helper cells, the immune system cannot recognize and coordinate a defensive response to diseases likeHIV. This is when a person is said to beimmunocompromised.
This article explains what CD4 T cells are, their role in HIV infection, and how they are involved in the diagnosis and treatment of HIV.
How the Immune System Works
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What Are CD4 Helper T Cells?
As each infectious agent has its own unique antigen, CD4 T cells are able to differentiate agents and trigger an immune response if an agent ever returns.
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.
There are three types of T helper cells that serve specific functions:
There are also specific CD4 T cells that “remember” past infections and launch a defensive response should the foreign attacker return. 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.
After producing thousands of new viruses, the infected cell eventually dies.
Over the course of years, as more and more CD4 T cells are killed, the immune system gradually loses its ability to fight off otherwise harmless infections. These so-calledopportunistic infectionsare what account for the majority of illnesses in people with advanced HIV.
(An example is a simple case oforal thrushthat can spread to the lungs, bloodstream, and distant organs in people who are immunocompromised.)
When enough CD4 T cells are killed and the immune system is fully compromised, a person is said to haveAIDS.
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.
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.
Diagnostic Value of CD4 T Cells
By measuring the number of CD4 cells circulating in your blood, a healthcare provider can determine the relative strength of your immune system if you have HIV. 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.
The results of the CD4 count are broadly interpreted as follows:
The CD4 count only describes the relative strength of your immune response. This is because it is possible to get a severe HIV-related infection, liketuberculosis, with a high CD4 count. It is also possible to have a low CD4 count and not get a severe HIV-related infection until your numbers drop below 100 or even 50 cells/mm3.
Can Your CD4 Count Return to Normal?With early treatment, a person with HIV can often rebuild their immune system and return to a normal CD4 count. This is more difficult if treatment is delayed. If treatment is started when the CD4 count is very low (under 100), the numbers may improve but never get above 500.
Can Your CD4 Count Return to Normal?
With early treatment, a person with HIV can often rebuild their immune system and return to a normal CD4 count. This is more difficult if treatment is delayed. If treatment is started when the CD4 count is very low (under 100), the numbers may improve but never get above 500.
Role of CD4 T Cells in HIV Treatment
In the past, treatment for HIV was delayed until the CD4 dropped to a certain level. This was due in part to the toxicity of early antiretroviral drugs as well as the speed at which drug resistance developed. These problems have been largely overcome.
As such, the CD4 count plays no role in the initiation of treatment or the selection of drugs best suited for your specific HIV type.
Where it does play a part is in the initiation ofprophylactic drugsused to prevent opportunistic infections. These antibiotic, antiviral, antifungal, or antiparasitic drugs are taken on a daily basis to prevent bacterial, viral, fungal, and parasitic opportunistic infection.
Examples include:
Summary
CD4 helper T cells are a type of white blood cell that coordinates the immune response. 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.
The CD4 count is a blood test used to measure CD4 T cells and the relative strength of your immune system. 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.
7 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Zhu X, Zhu J.CD4 T helper cell subsets and related human immunological disorders.Int J Mol Sci. 2020 Oct 28;21(21):8011. doi:10.3390/ijms21218011Luckheeram R. Zhou R, Verma A, et al.CD4+ T cells: differentiation and functions.Clinical and Developmental Immunology.2012:2012:925135. doi:10.1155/2012/925135Seng R, Goujard C, Krastinova E.; et al.Influence of lifelong cumulative HIV viremia on the long-term recovery of CD4+ count and CD4+/CD8+ ratio among patients on combination antiretroviral therapy.AIDS. 2015;29(5):595-607. DOI: 10.1097/QAD.0000000000000571.National Institutes of Health.Starting antiretroviral therapy early improves outcomes for HIV-infected individuals.Institute of Medicine.Low CD4 count as an indicator of disability.U.S. Department of Veterans Affairs.CD4 count (or T-cell count).Dyer M, Kerr C, McGowan JP, et al.Table 6.Prophylaxis for opportunistic Infections in adults With HIV. In:Comprehensive Primary Care for Adults With HIV [Internet]. Baltimore MD: John Hopkins University; 2021.
7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Zhu X, Zhu J.CD4 T helper cell subsets and related human immunological disorders.Int J Mol Sci. 2020 Oct 28;21(21):8011. doi:10.3390/ijms21218011Luckheeram R. Zhou R, Verma A, et al.CD4+ T cells: differentiation and functions.Clinical and Developmental Immunology.2012:2012:925135. doi:10.1155/2012/925135Seng R, Goujard C, Krastinova E.; et al.Influence of lifelong cumulative HIV viremia on the long-term recovery of CD4+ count and CD4+/CD8+ ratio among patients on combination antiretroviral therapy.AIDS. 2015;29(5):595-607. DOI: 10.1097/QAD.0000000000000571.National Institutes of Health.Starting antiretroviral therapy early improves outcomes for HIV-infected individuals.Institute of Medicine.Low CD4 count as an indicator of disability.U.S. Department of Veterans Affairs.CD4 count (or T-cell count).Dyer M, Kerr C, McGowan JP, et al.Table 6.Prophylaxis for opportunistic Infections in adults With HIV. In:Comprehensive Primary Care for Adults With HIV [Internet]. Baltimore MD: John Hopkins University; 2021.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Zhu X, Zhu J.CD4 T helper cell subsets and related human immunological disorders.Int J Mol Sci. 2020 Oct 28;21(21):8011. doi:10.3390/ijms21218011Luckheeram R. Zhou R, Verma A, et al.CD4+ T cells: differentiation and functions.Clinical and Developmental Immunology.2012:2012:925135. doi:10.1155/2012/925135Seng R, Goujard C, Krastinova E.; et al.Influence of lifelong cumulative HIV viremia on the long-term recovery of CD4+ count and CD4+/CD8+ ratio among patients on combination antiretroviral therapy.AIDS. 2015;29(5):595-607. DOI: 10.1097/QAD.0000000000000571.National Institutes of Health.Starting antiretroviral therapy early improves outcomes for HIV-infected individuals.Institute of Medicine.Low CD4 count as an indicator of disability.U.S. Department of Veterans Affairs.CD4 count (or T-cell count).Dyer M, Kerr C, McGowan JP, et al.Table 6.Prophylaxis for opportunistic Infections in adults With HIV. In:Comprehensive Primary Care for Adults With HIV [Internet]. Baltimore MD: John Hopkins University; 2021.
Zhu X, Zhu J.CD4 T helper cell subsets and related human immunological disorders.Int J Mol Sci. 2020 Oct 28;21(21):8011. doi:10.3390/ijms21218011
Luckheeram R. Zhou R, Verma A, et al.CD4+ T cells: differentiation and functions.Clinical and Developmental Immunology.2012:2012:925135. doi:10.1155/2012/925135
Seng R, Goujard C, Krastinova E.; et al.Influence of lifelong cumulative HIV viremia on the long-term recovery of CD4+ count and CD4+/CD8+ ratio among patients on combination antiretroviral therapy.AIDS. 2015;29(5):595-607. DOI: 10.1097/QAD.0000000000000571.
National Institutes of Health.Starting antiretroviral therapy early improves outcomes for HIV-infected individuals.
Institute of Medicine.Low CD4 count as an indicator of disability.
U.S. Department of Veterans Affairs.CD4 count (or T-cell count).
Dyer M, Kerr C, McGowan JP, et al.Table 6.Prophylaxis for opportunistic Infections in adults With HIV. In:Comprehensive Primary Care for Adults With HIV [Internet]. Baltimore MD: John Hopkins University; 2021.
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