Conditions That Cause Lymphocytosis

July 18, 2023

Lymphocytosis is a term used to describe a condition in which an individual has a higher than normal amount of lymphocytes in their blood. Lymphocytes are white blood cells that fight off pathogens and reside in the lymphatic system. They do this by differentiating into memory cells to recognize pathogens the body has seen before and by differentiating into plasma cells that make antibodies to fight the pathogen off. While a high lymphocyte count is relatively normal following a recent infection, it is not normal for it to stay elevated. When the lymphocyte count exceeds three thousand lymphocytes in a microliter of blood, it is lymphocytosis. No symptoms present with lymphocytosis itself, but the symptoms of the underlying cause may be apparent. A complete blood count with differential can help a physician determine if an individual is affected lymphocytosis. A bone marrow biopsy may also be utilized to help identify the underlying cause of an individual's lymphocytosis.

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Whooping Cough

Whooping cough (pertussis) is a highly contagious infection of the respiratory tract. The hallmark symptoms of whooping cough include a severe hacking cough trailed by a 'whoop' sound upon inhalation. A bacteria called Bordetella pertussis causes whooping cough. This bacteria has a specialized and unique ability to impair the function of the affected individual's immune system through its actions on lymphocytes. While the exact mechanism of how whooping cough induces lymphocytosis is not clear, it is known to be associated with the production increase in mIL-4 or interleukin-4 triggered by the pertussis virus. The toxin produced by the pertussis bacteria causes phagocyte cells to make too much cyclic AMP by converting ATP or cellular energy. This malfunction results in a disruption in signaling mechanisms the immune system uses to respond to infection. Because of these signaling disturbances, the bacteria have a selective influence on the ability of lymphocytes to enter the lymph nodes. When lymphocytes cannot enter the lymphatic system, they accumulate in the affected individual's blood causing a lymphocyte count of over four thousand per microliter of blood.

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Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia is a malignancy that develops in an affected individual's blood and bone marrow with no clear cause and quickly progresses in the absence of treatment. This type of leukemia occurs when a stem cell in the bone marrow that matures into a red blood cell, white blood cell, or platelet, acquires a genetic DNA injury. The DNA injury of the cell causes alteration or mutation in the part that provides the cell with instructions on how to grow, multiply, and die. The mutated DNA results in the development of malignancy. The malignant cell reproduces in an unmanageable fashion, making billions of lymphoblasts that infiltrate and invade the affected individual's bone marrow and bloodstream. Lymphoblasts are abnormal types of lymphocytes that are larger than normal and fail to function, stop the production of healthy cells, grow more rapidly than healthy cells, and effectively outlive healthy cells. The accumulation of these lymphoblasts in the blood of the affected individual can cause them to develop anemia, neutropenia, or thrombocytopenia. Chemotherapy is one of the only ways that these abnormal malignant lymphocytes can be eliminated from the body.

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Tuberculosis is an infection caused by a bacterium called mycobacterium tuberculosis. This type of infection usually has the biggest effect on the lungs but may cause problems in other parts of the body as well. Tuberculosis is highly contagious through contact with an affected individual's saliva particles in a sneeze, cough, or spit. Tuberculosis can last for between six and nine months with appropriate medical intervention. Tuberculosis is arbitrated by lymphocytes called CD4 T lymphocytes. Phagocytes cannot mediate this type of infection on their own because mycobacterium tuberculosis can grow in the vacuoles of phagocytes. CD4 T lymphocytes and CD8 lymphocytes are summoned to the scene to help eliminate tuberculosis bacteria as an alternative. The highest number of lymphocytes present in the body during a tuberculosis infection occurs within the first few weeks of a patient's illness. Other than the evasive nature of the bacteria that causes this infection, the mechanism of increased numbers of lymphocytes in the body from tuberculosis is not entirely clear. Only some patients who contract this infection will experience elevated levels of lymphocytes in their body, as the condition does not form in all tuberculosis patients.

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Chagas Disease

Chagas disease is a parasitic infection caused by the parasite called Trypanosoma cruzi, which is native to Latin America. Chagas disease is contagious and can be spread through a bite from a triatomine bug, contaminated food, organ donation, blood transfusion, or from mother to an unborn child during pregnancy. Symptoms that may manifest in affected individuals include fever, body aches, appetite loss, vomiting, swollen eyelid, fatigue, headache, diarrhea, and a rash. The symptoms of Chagas disease usually last anywhere from a couple of weeks to a couple of months, but the pathogen stays in the body for decades without treatment. This parasite causes an immune response in the body that is variable and complex in comparison to other pathogens and parasites. The levels of lymphocytes become unbalanced in the immunity involved organs during this infection, with different levels in the spleen, thymus, and blood. These imbalances are attributed to the different rates of expansion of lymphocytes in each respective organ. The rate of lymphocyte expansion in the blood, spleen, and thymus are dictated by the production of cytokines in each organ and rate of cell apoptosis. It is also suggested that individuals with Chagas disease have trouble clearing out antigen-specific lymphocytes, which can also contribute to the development of lymphocytosis.

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Infectious Mononucleosis

Infectious mononucleosis is a term used to describe a set of symptoms in an individual that is the result of an infection by Epstein-Barr virus. This virus can be transmitted from one person to the next through contact with an infected individual's saliva. Classic mono symptoms usually manifest four to six weeks following initial exposure to the virus. The actual mono symptoms themselves last a duration of between one and two months. Symptoms include fever, swollen lymph nodes, fatigue, swollen tonsils, sore throat, headache, muscle weakness, and night sweats. It can be hard to tell the difference between mono and other viruses such as the flu in affected individuals. A complete blood count can be done to check for elevated lymphocyte levels, which indicate the individual has mononucleosis. Epstein-Barr virus can invade and infect lymphocytes in the body of an infected individual. The virus populates in these white blood cells and utilizes them to rapidly replicate itself, thus causing rapid multiplication of this type of cell. This virus usually causes a proliferation of the B lymphocytes rather than the T lymphocytes.

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