CD27+ Test

Your immune system keeps a running record of every infection it has fought, every vaccine you have received, and every threat it is currently tracking. Much of that record lives on the surface of specific immune cells, marked by a protein called CD27. Counting these cells, or measuring the soluble version of this protein in your blood, gives a window into how active and experienced your immune system actually is.

This is not a routine test you would find on a basic checkup panel. It is a specialized immune readout used in research and specialty clinics to track conditions ranging from autoimmune disease to cancer immunotherapy response. For someone paying attention to immune health, infection susceptibility, or how their body is responding to a complex therapy, this number can show patterns that standard labs do not.

What CD27+ Actually Measures

CD27 (cluster of differentiation 27) is a receptor on the surface of certain B cells (the cells that make antibodies) and T cells (the cells that coordinate immune attacks). When a CD27+ count is reported, the lab is using flow cytometry, a technique that uses lasers and fluorescent tags to count specific cell types in a blood sample, to identify how many of your lymphocytes carry this marker.

On B cells, CD27 generally identifies memory B cells, the long-lived cells that remember past infections and vaccinations. On T cells, CD27 marks cells that are still relatively young in their differentiation journey and capable of strong immune responses. A related measurement, soluble CD27 (sCD27), is the shed form of this receptor that circulates in blood or cerebrospinal fluid, reflecting how actively immune cells are engaging their counterparts.

Immune Aging and Memory

As you age, the balance of immune cells shifts in ways that this marker captures. In a study of 84 healthy adults, CD27+ memory B cells declined and CD27 negative naive B cells (which are also more resistant to programmed cell death) increased with age, suggesting age-related disturbances in how the body builds and maintains immune memory.

In one study of 597 octogenarians (people in their 80s), a higher count of a specific T cell subset that lacks CD27 but retains CD28 was inversely related to mortality, regardless of cytomegalovirus status. This is one of several signals that the way CD27+ and CD27 negative populations balance against each other is part of how immune aging plays out.

Reconciling the Memory and Aging Signals

At first glance, the data can look contradictory. Loss of CD27+ memory B cells with age sounds bad, but a related T cell shift away from CD27+ has been linked to lower mortality in the very old. The framework that resolves this is straightforward: CD27 is not a simple good or bad marker. It is a phenotype indicator. Different CD27-defined populations carry different meaning depending on which cell type, which disease, and which life stage you are looking at. Read the result in context, not as a single verdict.

Autoimmune Disease Activity

In several autoimmune conditions, CD27-defined cell subsets track how active the disease is. In a study of 190 people with systemic lupus erythematosus (SLE), the frequency of CD21 negative CD27 negative B cells in blood was associated with disease activity independently of conventional blood markers like complement and autoantibodies. In rheumatoid arthritis, IgD negative CD27 negative memory B cells are increased and tend to normalize with effective treatment.

In multiple sclerosis, soluble CD27 measured in cerebrospinal fluid (the fluid bathing the brain and spinal cord) correlated with active inflammatory T cells and dense CD27+ T cell infiltrates in lesions. A study of 184 people supported using this CSF measurement as a marker of T cell driven lesion activity. In a separate cohort of 94 children with demyelinating syndromes (early nervous system inflammation), higher CSF sCD27 was associated with later confirmed multiple sclerosis.

Cancer and Immunotherapy Response

CD27 measurements are increasingly used as predictive markers in cancer immunotherapy. In 210 people with metastatic melanoma treated with anti-PD1 immunotherapy, those with baseline plasma soluble CD27 above 100 U/mL had median progression free survival of 3.2 months versus 9.2 months for those at or below this threshold. Median overall survival was 13.6 months in the high group versus not reached at 60 months in the low group. The receiver operating characteristic curve, a measure of how well a test separates outcomes where 1.0 is perfect and 0.5 is useless, was 0.73 for predicting one year survival.

In renal cell carcinoma, plasma soluble CD27 reflects tumor CD27 to CD70 interactions, and high levels predicted resistance to PD1 blockade in a study of 106 patients. In multiple myeloma, low CD27 expression on malignant plasma cells in a study of 121 people was associated with high risk disease subgroups, while complete remission correlated with higher proportions of CD27+ plasma cells.

Lymphoma Risk Years in Advance

Some of the most striking data on this marker come from prospective cohorts that drew blood years before disease appeared. In three Chinese prospective cohorts comparing 218 future lymphoma cases with 218 matched controls, people in the highest quartile of soluble CD27 had about 4.5 times the odds of developing non-Hodgkin lymphoma compared to the lowest quartile, with a strong dose response across quartiles.

Even when the blood was drawn more than 10 years before diagnosis, the predictive signal held. People in the top tertile had nearly 3 times the odds of future lymphoma compared to the lowest tertile. A separate European nested case control study supported the link, particularly for chronic lymphocytic leukemia. The implication: chronic B cell activation, captured by sCD27, can quietly precede a lymphoma diagnosis by a decade.

Infection and Immune Activation

In tuberculosis, the pattern of CD27 expression on T cells helps separate active disease from latent infection. In a study of 376 people, a CD27 negative CD38+ interferon gamma producing CD4+ T cell subset reached a sensitivity of 0.869 (catching 87 out of 100 cases) and specificity of 0.849 (correctly clearing 85 out of 100 non-cases) for active tuberculosis. In a separate study of 221 people, an Mtb specific CD38+ CD27 negative TNF alpha+ CD4+ T cell subset was a robust biomarker for diagnosing tuberculosis and assessing cure.

In HIV, plasma soluble CD27 tracks systemic immune activation, rises with viral load, and normalizes with effective antiretroviral therapy. In 426 people with HIV starting treatment, higher soluble CD27 was associated with increased risk of non-AIDS morbid events, suggesting it captures immune activation that matters for long term health beyond the virus itself.

Reference Ranges

This is a Tier 3 marker. Standardized clinical reference ranges do not yet exist across labs, and the right cutpoint depends heavily on which subset you are measuring (B cells versus T cells), what units the lab uses (absolute counts, percentages, or soluble protein concentration), and the disease context. Different studies use different gating strategies and panels, so numbers do not transfer cleanly between labs. The values below come from specific research populations and assays. They are illustrative orientation, not universal targets.

Source: melanoma cutpoints from melanoma anti-PD1 studies; lymphoma quartiles from Chinese prospective cohorts; aging data from Chong et al. 2005. Compare your results within the same lab over time for the most meaningful trend, since assay differences between labs can produce different absolute numbers from the same blood.

Tracking Your Trend

A single CD27+ value carries far less information than a trend. Immune cell populations shift in response to recent infections, vaccinations, sleep, stress, and treatment effects. The most useful pattern to watch is the direction of change over months and years, especially if you are managing a known autoimmune condition, on immunotherapy, or tracking immune health proactively.

A reasonable cadence: get a baseline, retest in 3 to 6 months if you are making meaningful changes (starting a biologic, beginning immunotherapy, recovering from a major immune insult), then at least annually. If you are using this marker to monitor a condition like myasthenia gravis on rituximab, where CD27+ memory B cell repopulation has been shown to predict relapse, your specialist may set a much shorter retesting interval, sometimes every few months.

When Results Can Be Misleading

A single reading can be distorted by factors unrelated to your underlying immune health:

• Recent acute infection or vaccination: in a study of CD27++ plasma cells, peripheral blood plasma cell counts showed a transient expansion during acute bacterial infections. Testing within days to a few weeks of an infection or vaccine can produce numbers that do not reflect your steady state.
• Acute exercise: in a study of 16 people, vigorous exercise mobilized B cells into the bloodstream, including immature CD27 negative populations. A workout shortly before the draw can transiently shift the balance of CD27+ to CD27 negative cells.
• Active immunosuppressive therapy: drugs like rituximab deplete B cells substantially and reshape CD27 defined memory subsets, so timing of the test relative to dosing matters for interpretation.
• Lab assay differences: flow cytometry panels, gating strategies, and antibody clones differ between labs, which can produce meaningfully different absolute numbers from the same blood. Comparing across labs is unreliable.

What to Do With an Abnormal Result

Because this is a Tier 3 marker without standardized cutpoints, no single value should drive a clinical decision in isolation. Use the result as one piece of a broader picture. If your CD27+ memory B cells are unexpectedly low and you have a history of recurrent infections or unusually severe Epstein Barr virus disease, that pattern is worth investigating with an immunologist, including testing for primary immunodeficiency syndromes.

If soluble CD27 is high in a cancer immunotherapy context, that may shift the conversation with your oncologist toward combination therapy rather than single agent PD1 blockade. If you are tracking an autoimmune condition, persistent abnormalities in CD27 defined subsets alongside disease activity scores can support escalating or changing therapy. In all cases, this number complements rather than replaces standard workups: a complete blood count, immunoglobulin levels, and disease specific autoantibodies should be in the picture too.