Lymphocytes: Function, Definition, Levels & Ranges

Lymphocytes play a crucial role in our immune system as a specialized type of white blood cell. These cells are instrumental in defending the body against various threats, including malignant cells, foreign pathogens, and invading microorganisms. A routine blood test conducted by your doctor can measure your lymphocyte count. 

What are Lymphocytes?

Lymphocytes are a type of body’s defence cells or white blood cells, only called WBCs, that play a crucial role in the body’s immunity against harmful particles and microbes. These specialised cells recognise and combat foreign substances, such as viruses, bacteria, and abnormal cells. They are essential to the lymphatic system, a network of vessels, tissues, and organs that protect the body from numerous infections and diseases.

Lymphocytes are primarily generated in the bone marrow and are classified into two main types: 

• B cells secrete antibodies, proteins that can neutralise and destroy pathogens. 
• On the other hand, T cells are responsible for cell-mediated immunity, which involves the direct destruction of infected or abnormal cells.

 The following are three main types of T cells:

• Helper T-cells: These cells coordinate the immune response by stimulating other cells, such as B cells and cytotoxic T cells.
• Cytotoxic T-cells: These cells directly attack and destroy infected or abnormal cells.
• Regulatory T-cells: These cells help regulate the immune response & prevent it from becoming too strong or too weak.

What is the Function of Lymphocytes?

The principal function of lymphocytes is to protect the body from harmful disease-causing agents and abnormal cells. Here are some of the key responsibilities of lymphocytes:

• Antibody Production: B cells produce antibodies that recognise and neutralise specific pathogens or toxins.
• Cell-mediated Immunity: T cells, particularly cytotoxic T cells, can directly attack and destroy infected or abnormal cells.
• Immune Regulation: Regulatory T cells help maintain a balance in the immune response.
• Immunological Memory: Some lymphocytes can develop into memory cells, allowing the body to mount a faster and more effective immune response if exposed to the same pathogen in the future.

Where are Lymphocytes Located?

Lymphocytes are found throughout the body, but they are primarily concentrated in the lymphatic system, which includes:

• Lymph Nodes: These small, bean-shaped organs are situated throughout the body and act as filters for the lymphatic system. They trap pathogens and abnormal cells, allowing lymphocytes to accumulate and mount an immune response.
• Spleen: The spleen is a small lymphatic organ located in the upper-left abdomen. The spleen filters blood, removes old or damaged red blood cells, and traps pathogens and abnormal cells for lymphocytes to respond to.
• Thymus: The thymus is a small organ situated in the upper chest region. It is elementary for the maturation and development of T cells.
• Bone Marrow: The bone marrow is the principal site of lymphocyte production, particularly for B cells.
• Lymphatic Vessels: These vessels transport lymph fluid, which contains lymphocytes, throughout the body.

Lymphocytes also circulate in the bloodstream and are present in other tissues and organs, such as the intestines, lungs, and skin.

What is the Normal Range of Lymphocytes?

The normal value range of lymphocytes in the blood can vary & depends on factors such as age, gender, and overall health. However, generally, the lymphocyte’s normal range is as follows:

• Adults: 1,000 – 4,800 lymphocytes per microlitre (μL) of blood
• Children: 3,000 – 9,500 lymphocytes per μL of blood
• Infants: 4,000 – 10,500 lymphocytes per μL of blood

What Does a High Level of Lymphocytes Mean?

A high lymphocyte level, also known as lymphocytosis, can indicate various conditions or situations. Here are some potential causes of a high absolute lymphocyte count:

• Viral Infections: Common cold, influenza, or mononucleosis can cause an increase in lymphocyte production as the body tries to fight off the virus.
• Bacterial Infections: Certain bacterial infections, such as tuberculosis or pertussis (whooping cough), can also lead to an elevated lymphocyte count.
• Autoimmune Disorders: In rheumatoid arthritis, lupus, or Hashimoto’s thyroiditis, the immune system mistakenly attacks the body’s own tissues, increasing lymphocyte production.
• Leukaemia: Some types of leukaemia, particularly chronic lymphocytic leukaemia (CLL), can cause a significant increase in the number of lymphocytes in the blood.
• Stress or Physical Exertion: Intense physical or emotional stress can temporarily increase lymphocyte levels as part of the body’s natural response.

It’s important to note that a slightly elevated lymphocyte count may not necessarily indicate a serious condition, and further testing may be required to determine the underlying cause, says Dr. Mahesh Rajashekaraiah.

What Does a Low Level of Lymphocytes Mean?

A low lymphocyte level, also known as lymphocytopenia, can be a sign of various health conditions. Here are some potential causes of a low lymphocyte count:

• Viral Infections: HIV/AIDS can suppress the production of lymphocytes, leading to a low count.
• Autoimmune Disorders: Conditions like rheumatoid arthritis, lupus, or Sjögren’s syndrome can cause the immune system to attack and destroy lymphocytes, resulting in a low count.
• Radiation or Chemotherapy: Radiation therapy or chemotherapy given as cancer treatment can damage the bone marrow, leading to a decrease in lymphocyte production.
• Malnutrition: A deficiency of essential nutrients, such as protein, vitamin B12, or folate, can impair lymphocyte production and function.
• Congenital Disorders: Certain inherited disorders, like severe combined immunodeficiency (SCID), can result in a lack of functional lymphocytes from birth.
• Medications: Some medicines, such as corticosteroids or immunosuppressants, can suppress the immune system and lower lymphocyte levels.

What are Common Tests to Check the Health of Lymphocytes?

Several tests can evaluate the health and function of the lymphocytes. Here are some common tests:

• Complete Blood Count (CBC): A CBC is a routine blood investigation that measures the levels of various blood cells, including lymphocytes. This test can provide information about the overall lymphocyte count and help detect abnormalities.
• Lymphocyte Subset Analysis: This test measures the different types of lymphocytes (B cells, T cells, and their subtypes) present in the blood. It can help identify imbalances or abnormalities in the lymphocyte populations, which may indicate specific immune system disorders.
• Immunoglobulin Levels: This investigation measures the levels of different types of antibodies (immunoglobulins) produced by B cells. Abnormal levels of immunoglobulins can indicate problems with the immune system’s ability to produce antibodies effectively.
• Flow Cytometry: This advanced technique uses lasers and fluorescent markers to analyse and identify different types of cells and provide detailed information about the lymphocyte populations and their functional state.
• Lymphocyte Function Tests: These tests evaluate the ability of lymphocytes to respond to specific stimuli or perform their intended functions, such as antibody production or cytotoxic activity. They can help diagnose immune system disorders affecting lymphocyte function.
• Biopsy: In some cases, a biopsy of lymph nodes or other lymphatic tissues may be performed to examine the lymphocytes and assess for abnormalities or malignant cells.

What are Common Symptoms of Lymphocyte Conditions?

Abnormalities in lymphocyte levels or function can lead to various symptoms, depending on the underlying condition. Here are some common symptoms associated with lymphocyte conditions:

• Recurrent Infections: A low lymphocyte count or impaired lymphocyte function can increase the risk of frequent or severe infections, as the body’s ability to fight off pathogens is compromised.
• Swollen Lymph Nodes: Enlarged lymph nodes, or lymphadenopathy, can occur when lymphocytes accumulate in response to an infection or other immune system stimuli.
• Fatigue: Chronic fatigue or weakness can be due to various lymphocyte disorders, such as lymphoma or autoimmune conditions.
• Fever: Persistent or recurrent fevers can indicate an underlying infection or immune system disorder involving lymphocytes.
• Skin Rashes or Lesions: Certain autoimmune conditions, like lupus or dermatomyositis, can cause skin rashes or lesions.
• Joint Pain or Swelling: Autoimmune disorders, such as rheumatoid arthritis, cause joint inflammation & pain due to the immune system’s attack on the joints.
• Unexplained Weight Loss: Rapid or unexplained weight loss can be a symptom of certain lymphocyte disorders, such as lymphoma or HIV/AIDS.

Conclusion

Lymphocytes are essential immune system components, playing a foremost role in protecting us from harmful pathogens & abnormal cells. Understanding the function, levels, and ranges of lymphocytes is essential for maintaining overall health. By monitoring lymphocyte levels through regular blood tests & seeking medical attention from an expert in SPARSH, one of the best bone marrow transplant hospitals in Bangalore,  for any concerning symptoms, individuals can take definitive steps to maintain their immune system healthy and address underlying conditions that may affect lymphocyte function. 

FAQs

What happens if lymphocytes are high?

A high level of lymphocytes, also known as lymphocytosis, can indicate various conditions or situations, such as viral or bacterial infections, autoimmune disorders, leukaemia, or a temporary response to stress or physical exertion. 

What if lymphocytes are low?

A low level of lymphocytes, or lymphocytopenia, can be due to various health issues, such as viral infections (like HIV/AIDS), autoimmune disorders, radiation or chemotherapy treatment, malnutrition, congenital disorders, or the use of certain medications. A low lymphocyte count can increase the risk of infections, as the body’s ability to fight pathogens is compromised.

What is the normal range of lymphocytes?

The normal lymphocyte range in the blood is: 

• Adults: 1,000 – 4,800 lymphocytes per μL of blood
• Children: 3,000 – 9,500 lymphocytes per μL of blood
• Infants: 4,000 – 10,500 lymphocytes per μL of blood