Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
This test measures the proportion of your circulating T lymphocytes that express the CD8 marker. The laboratory uses flow cytometry, tagging white blood cells with antibodies to CD45 (to identify leukocytes), CD3 (to select T cells), and CD8 (to identify cytotoxic T cells).
The result is reported as a percentage of the lymphocyte population and reflects the size of your cytotoxic T cell compartment at the time of the blood draw.
CD8 T cells help your immune system clear virus-infected and cancerous cells, and they change with infections, immune deficiencies, autoimmune conditions, and immune-modulating treatments. Clinicians use this test to assess immune status in settings such as HIV care, evaluation of suspected primary or secondary immunodeficiency, post-transplant monitoring, and follow up of inflammatory or hematologic disorders.
It is often interpreted together with CD4 T cells, the CD4 to CD8 ratio, and absolute lymphocyte counts to build a fuller picture of immune health.
Your result is interpreted in the context of age-specific reference intervals, your medical history, and other laboratory findings. A higher or lower percentage can be seen with recent infections, chronic viral infections, immune suppression, autoimmune disease, hematologic conditions, or effects of medications.
If a result is unexpected, your clinician may confirm with repeat testing, review recent illnesses or vaccinations, check the absolute CD8 count and other lymphocyte subsets, and consider additional immune testing or medication adjustments as needed.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Acute illness and recent immunization can transiently shift lymphocyte subsets, including CD8 T cells. Let your clinician know about recent fevers, respiratory or gastrointestinal symptoms, and any vaccines received in the prior few weeks.
Corticosteroids, chemotherapy, calcineurin inhibitors, anti-proliferative agents, monoclonal antibodies targeting lymphocytes, and some biologics can lower or redistribute T cells. Antiretroviral therapy and immune reconstitution can change CD8 dynamics over time.
Flow cytometry requires fresh whole blood. Delays, extreme temperatures, or improper anticoagulant can degrade cell markers and skew results. Whenever possible, draw and process the sample promptly and at a consistent time of day.
Normal distributions of lymphocyte subsets vary with age, especially in infancy and childhood. Reference intervals are age specific, so interpretation always accounts for how old you are.
Acute stress, strenuous exercise, and conditions such as autoimmune disease, chronic viral infection, and lymphoproliferative disorders can alter CD8 proportions. Share any recent major exertion or new diagnoses with your care team.
Physiologic immune changes during pregnancy may influence lymphocyte subsets. If you are pregnant or recently postpartum, your clinician will interpret results in that context.
References