Blood tests are helpful tools that make sure the body is functioning properly, but they can sometimes seem like they’re written in another language: different ranges, values, abbreviations, and jargon. Lymphocyte count is an important measure included in your blood test results. If you recently received a blood test with a low lymphocyte count, you may be wondering: what does low lymphocytes mean? Here we decipher what this means on a blood test, and when to worry about low lymphocytes.
What Are Lymphocytes?
Understanding the role of lymphocytes in your body clarifies the meaning of a low lymphocyte count on your blood test.
Lymphocytes are a type of white blood cells, and your blood test will also include a value for your total white blood cell count. White blood cells comprise your immune system’s defense army and include lymphocytes as well as neutrophils, monocytes, eosinophils, and basophils. The immune system dispatches white blood cells to fight off foreign invaders, which are also referred to as antigens.
Antigens can be anything that activates your immune response, including:
In addition to fighting off these pathogens, the immune system also recognizes and destroys infected and malfunctioning cells in your body.
There are about 2 trillion lymphocytes in your body and can be found in the blood and lymph fluid. Lymph travels through capillary walls to deliver lymphocytes to all areas of the body and are critical to your body’s two types of immune response: adaptive and innate.
Lymphocytes are able to develop and specialize so that they target a specific invader, a system that is called adaptive immune response. This process plays a role in vaccinations. For example, a yearly flu shot introduces the flu virus to your body, so that your lymphocytes can learn to recognize and attack that particular flu virus before it makes you sick. Lymphocytes also play a role in the innate immune response, which is your body’s generalized immune response that identifies infected cells and facilitates adaptive immunity.
Types of Lymphocytes
Lymphocytes can be further categorized into T lymphocytes, B lymphocytes, and natural killer cells.
- T lymphocytes: These lymphocytes, also called T cells, are manufactured in the thymus, a small gland that sits between your lungs and beneath your sternum. T cells are crucial to your body’s adaptive immune response.
- B lymphocytes: These lymphocytes, also called B cells, are manufactured in the bone marrow and participate in adaptive immunity.
- Natural killer cells: These are produced in many locations including bone marrow, spleen, tonsils, and thymus. Even though natural killer cells make up a smaller percentage of your body’s total lymphocytes, they are critical for innate immunity and help kill infected cells and tumor cells.
What Does it Mean When Your Lymphocytes Are Low?
For healthy adults, the number of lymphocytes per microliter of blood should fall between 1,500 and 4,800. Lymphocytopenia – also called lymphopenia – describes the condition of low lymphocytes. To meet the criteria for lymphocytopenia, your lymphocyte count must fall below 1,500. A low lymphocyte count indicates that your immune system is worn out or functioning at a sub-optimal level, leaving you at an increased risk of infection. This is called immunodeficiency.
A standard complete blood count (CBC) test doesn’t show the levels of each type of lymphocyte. Your doctor may want to do a follow-up test to evaluate the levels of the different lymphocytes. This test is called a lymphocyte subset panel.
First, let’s look at cases of low lymphocytes that are not necessarily a cause for concern.
Minor Cases of Lymphocytopenia
Minor cases of lymphocytopenia are usually acute and improve on their own or with small lifestyle changes. In these cases, lymphocytopenia will be mild, with a lymphocyte count that most likely falls just a little below the normal range. You may have no symptoms of mild lymphocytopenia.
Common causes of low lymphocytes include viral infections and stress. (1)
The flu or common cold may cause your lymphocyte count to dip below the lower limit. If you are experiencing respiratory symptoms like coughing, congestion, and a fever, chances are you have a viral infection. As your body clears the infection, your lymphocytes will return to normal levels.
Maybe you’ve been sleep deprived while you prepare for a huge presentation at work or running long distances to train for a marathon. Stress, regardless of the origin, can temporarily compromise your immune system. For stress-induced lymphocytopenia, catching up on sleep, fueling your body with healthy foods, and slowing down on rigorous physical training should help your lymphocyte levels return to normal.
Signs of Something More Serious
In some cases, low lymphocytes may signify a more serious underlying cause.
Here are a few red flags: (1)
- Your reading falls far below the normal lower limit
- Your lymphocyte levels are chronically low
- You get frequent and recurrent illnesses
- Your infections result from exposure to pathogens that a healthy immune system can easily fight off
- Consistently swollen lymph nodes
- You are experiencing other chronic symptoms like unexplained weight loss and extreme fatigue
If your doctor finds any concerning signs associated with your lymphocyte level, he or she will conduct other tests like the lymphocyte subset panel to gain more information and uncover the root cause.
Here we outline more serious potential causes of lymphocytopenia. Though some may be life-threatening, others are managed with carefully planned medical interventions and lifestyle changes. The key is not to panic until you talk with your doctor, undergo necessary tests, consult with specialists if necessary, and receive a proper and thorough diagnosis. Your health care team will then prescribe medications and dietary changes to treat the underlying cause.
Many gastrointestinal disorders like inflammatory bowel syndrome and celiac disease can inhibit normal protein absorption in the digestive system. This condition, called protein-losing enteropathy, can negatively impact the immune system. Research shows that individuals with protein-losing enteropathy have a higher risk of lymphopenia. (2)
Alcoholic Liver Disease and Liver Cirrhosis
Scientific studies reveal that alcoholic liver disease and alcohol abuse can be associated with lymphocytopenia. A study published in the World Journal of Hepatology showed that in comparison to controls, men with alcoholic liver disease had lower lymphocyte counts. (3) Research also shows that liver cirrhosis causes lymphopenia by inhibiting T cell and B cell production and altering lymphocyte function. (4)
If you have low lymphocytes combined with elevated liver enzymes, this may suggest the progression of liver disease, especially if you are a heavy drinker or have a history of liver disease.
Undernutrition and Eating Disorders
Globally, inadequate intake of nutritious foods and subsequent malnutrition is a very common cause of low lymphocytes. Your body needs sufficient vitamins, minerals, and protein to produce healthy lymphocytes and other white blood cells. Strict diets, calorie restriction, and fasting may also cause lymphocytopenia. Eating disorders like anorexia and bulimia deprive the body of essential nutrients for immune function, including protein, vitamin A, and vitamin D. Your doctor and a nutritionist can help determine if you’re getting enough nutrients to support your immune system.
Severe Viral and Bacterial Infections
If a viral infection or bacterial infection is severe, it will compromise your immune system function and lead to low lymphocytes.
Serious viral infections associated with low lymphocytes include:
Serious bacterial infections associated with low lymphocytes include:
- Miliary tuberculosis
Cancer alters healthy immune functioning and several cancers are associated with lymphocytopenia.
- Leukemia cancers: These cancers affect the bone marrow and cause changes in red blood cells and platelets, and decrease lymphocyte levels. (6)
- Lymphoma cancers: These types of cancers specifically target lymphocytes and result in lymphocytopenia.
Lymphocytopenia May Be Caused by Medication
In some cases, lymphocytopenia may be a side effect of medication.
- Corticosteroids. These are used to manage severe allergic reactions and diseases like arthritis.
- Chemotherapy and radiation. These are aggressive treatments that are used to combat cancer.
- Opioids. Opioids are prescribed to manage pain associated with surgery recovery and severe pain conditions. Research shows that long term use of opioids results in immunosuppression. (7)
- Immunosuppressants. Drugs like interferon treat inflammatory and autoimmune diseases by lowering immune system activity. This may also cause lower lymphocyte levels.
If your medications are causing low lymphocytes, your doctor will monitor your lymphocyte levels and alter your treatment plan if needed.
Don’t Worry Unless You Need To
Many cases of lymphocytopenia are nothing to worry about and resolve with time. By assessing any co-occurring symptoms and circumstances, your doctor will be able to determine if your case of lymphocytopenia is a more serious health concern. In any case, if you sense something is a little off with your body, always ask your health care provider.