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CD4 and CD8

Also known as: T4 count; T-helper cells; T-suppressor cells; Cytotoxic T-cells
Formal name: CD4 lymphocyte count; CD8 lymphocyte count; CD4/CD8 ratio; CD4 percent
Related tests: HIV antibody; p24 antigen test; HIV viral load; HIV genotypic resistance testing; HIV phenotypic resistance testing

Common Questions

1.  How is HIV diagnosed?

HIV is usually screened for and diagnosed with an HIV antibody test about 2-8 weeks after exposure to the virus. If exposure is more recent, a p24 antigen test or an HIV viral load test may be used to detect the virus in your blood.

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2.  What are some common opportunistic infections I might get if I have HIV?

The Center for Disease Control (CDC) includes 26 opportunistic infections in its definition of AIDS. Click here for a list of some of the most common of these.

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3.  What are my treatment options if my CD4 count becomes too low?

You and your doctor should discuss your treatment options to determine what will work best for you. The Mayo Clinic webpage HIV/AIDS: Treatment and drugs has detailed information on various therapies.

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4.  Is a CD4 cell count used in conditions other than HIV?

Yes. It may be ordered when a patient has had an organ transplant, to help evaluate the effect of immunosuppressive medications. In transplantation, the immune system must be suppressed so that it does not attack the transplanted organ and cause rejection. In this case, it is desirable to have low levels of CD4 cells, and a decreased count shows that the drug is working. A CD4 count may be repeated periodically to monitor the effectiveness of therapy.

Evaluation of CD4 and CD8 cells may also be used to help classify lymphomas. Typically, several lymphocyte surface markers in addition to CD4 and CD8 are evaluated. The tests help determine whether the lymphoma is due to the proliferation of B cells or T cells and which specific type. This information is useful in determining appropriate therapy.

These tests may also help diagnose DiGeorge syndrome, a rare congenital disorder characterized by, among other things, low levels of T cells in the blood. For more information on DiGeorge syndrome, visit the Mayo Clinic website.

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