My Blood Test Results Showed Low Lymphocytes – What Does That Mean?

EDITOR’S NOTE … September is Blood Cancer Awareness Month.

By LESLIE POPPLEWELL, M.D., City of Hope Cancer Center Atlanta

A brief needle stick in the arm and a few vials later, your doctor has a report that tells them a lot about your overall health.

We are all fairly accustomed to routine complete blood count (CBC) tests — the various levels indicated in the results may inform a clinician about organ function, risk of heart disease or diabetes, clotting, infection and so much more. One particular area doctors measure in a CBC are lymphocyte levels. These can inform your doctor about how well your immune system is functioning to fight off harmful invaders and heal your body. When these levels are low, it may mean you are dealing with something temporary, like an infection or severe stress, or a lifelong condition or disease. Some patients may jump immediately to worrying about the possibility of cancer, but that is not always the case.

What are lymphocytes?

Lymphocytes are one type of white blood cells, a hardworking part of the immune system that help your body fight off invaders. These cells develop in your bone marrow before they mature and enter your bloodstream and lymphatic system to perform their duty.

The lymphocyte team consists of two main types: B cells and T cells.

• B cells create antibodies to target viruses, bacteria, parasites and other foreign intruders.
• T cells control your body’s immune system response to attack infected cells and tumors.

After encountering a foreign virus or bacteria, or “antigen,” some lymphocytes transform into “memory” cells to ensure the body remembers the antigen and can quickly react should it ever encounter those antigens again. Together, these special white blood cells form a mighty team that protect your body.

What does it mean when my lymphocyte levels are low?

Age, genetics and lifestyle all impact the total number of lymphocytes in your body, but overall they account for approximately 20 to 40% of your total blood volume. Changes in lymphocyte levels in the body usually indicate something is amiss, but it does not always equate to something serious or life threatening.

Low levels of lymphocytes is called lymphocytopenia. Lymphocytopenia can be temporary, or “acute,” when it is triggered by something often lifestyle related, such as catching the flu, enduring a significant amount of stress or even undergoing high-intensity exercise. These instances are not typically cause for concern and usually resolve on their own, with lifestyle changes or with medication to treat any infections. (Of note, these conditions may also trigger the opposite condition: lymphocytosis, or higher-than-average lymphocyte levels.)

If a doctor suspects the lymphocytopenia is “chronic,” or long-term/unresolved, they may pursue testing for more serious conditions, such as:

• Autoimmune disorders like lupus or rheumatoid arthritis
• Viral hepatitis
• HIV or AIDS
• Blood cancers such as lymphoma or leukemia

Are there any symptoms?

Most of the time, lymphocytopenia is discovered in routine CBC testing as an important step in an annual wellness exam with your primary care physician. Patients typically do not experience symptoms for low lymphocytes, but if they do, those symptoms may include (alone or in combination):

• Frequent infections, such as pneumonia
• Infections that typically wouldn’t cause problems in healthy immune systems
• Infections that won’t go away
• Swollen lymph nodes (particularly in the neck or groin)
• A larger-than-normal spleen
• Skin conditions, like eczema or alopecia (hair loss)
• Joint pain and swelling
• Signs of a viral infection (e.g., fever, cough or runny nose)

In these instances, a doctor will likely refer you to a hematologist, or a physician specializing in diseases of the blood, bone marrow and lymphatic system — areas intimately related to your lymphocytes. Hematologists can perform further evaluations to confirm your diagnosis and, if it is chronic, formulate a plan to increase lymphocyte counts to a healthy range by treating whatever is causing the decline. This can be accomplished through medication,  bone and stem cell transplants/therapy, and various other methods based upon the root cause.

Whether or not you should be concerned about low lymphocyte levels depends upon your genetics, your current health, if you’re symptomatic and various other individual factors. You can learn more about diseases of the blood on https://www.cityofhope.org/clinical-program/blood-cancers. If you have any concerns about your health, be it lymphocytopenia or otherwise, speak with your doctor as soon as possible.

Leslie Popplewell, M.D., is a hematologist and oncologist at City of Hope Cancer Center Atlanta. She serves as the medical director of their Hematology and Blood and Marrow Transplant department and leads their Blood Cancer Center. Additionally, she serves as the principal investigator for a number of clinical trials examining new lymphoma therapies including CAR T cells and phase 1 and first in human trials. She is also working on advanced transplant techniques for patients whose lymphoma has recurred. Popplewell joined the Atlanta cancer center in 2023 and previously served for over 20 years at City of Hope’s campus in Duarte, California, as hematologist, chief of the Division of Lymphoma, Department of Hematology & Hematopoietic Cell Transplantation and associate medical director of the Judy & Bernard Briskin Center for Clinical Research.