CD4/CD8 ratio
DECD4/CD8-Quotient
The CD4/CD8 ratio compares two kinds of T cell in your blood: CD4+ helper T cells versus CD8+ killer T cells. A healthy ratio is usually cited as about 1.5 to 2.5. In young, healthy adults, CD4+ cells outnumber the rest and coordinate the immune response, while CD8+ cells patrol for infected or cancerous cells. With age, especially if you carry the common CMV virus, certain CD8+ cells expand in large clones. That squeezes the ratio, and can even flip it below 1.0. An inverted ratio is tied to frailty, weak vaccine responses, and higher all-cause death in elderly groups and in people with HIV. So it is increasingly used as part of immune-risk profiling, in the context of immune aging (immunosenescence).
Last reviewed:
This definition is educational and is not medical advice, a diagnosis, or treatment. Talk to a doctor about any health decisions. Read our full medical disclaimer