A high lymphocyte count, or lymphocytosis, can be caused by mononucleosis, multiple myeloma, human immunodeficiency virus, cytomegalovirus infection, acute lymphocytic leukemia, chronic lymphocytic leukemia, vasculitis and other viral infections.Continue Reading
What Is a Lymphocyte?
Lymphocytes are white blood cells found in the immune system, and there are two main types. These are B cells and T cells, and they combine their efforts to fight off infection. Antibodies are produced by the B cells to attack toxins, viruses and bacteria. Any cells in the body that have become cancerous or overcome by viruses are destroyed by T cells, according to Healthline. In adults, a lymphocyte count significantly higher than 3,000 lymphocytes in a microliter of blood is generally considered to be lymphocytosis, notes the Mayo Clinic.
There are different types of B cells and T cells. Effector cells combat active infections when activated by antigens. Memory cells have the ability to recall past infections. If an antigen re-infects the body, memory cells are quickly activated.
B cells transform into plasma cells when an antigen is recognized, producing antibodies. T cells comprise cytotoxic, helper and regulatory T cells. Cancer cells, cells infected with an antigen or foreign cells, such as those from a transplant, are killed by cytotoxic T cells. The immune response of the other T cells and the B cells is directed by the helper T cells. The immune system is suppressed by the regulatory T cells so that perceived or actual antigens are not attacked by other white blood cells.
Where Do Lymphocytes Originate?
B cells and T cells come from bone marrow, originating from stem cells. Roughly 25 percent of the new lymphocytes stay in the bone marrow, transforming to B cells. The majority, however, move to the thymus. This is where they transform into T cells. Lymphocytes are continually produced by bone marrow, with most moving through the organs and tissues that comprise the lymphatic system, while some enter the bloodstream.
Obtaining and Understanding a Lymphocyte Count
A blood test can determine the level of lymphocytes. This is called a B and T cell screen. It is possible to have a high lymphocyte count and display no symptoms, notes the Mayo Clinic. If test results indicate a high lymphocyte count, a person's doctor may perform additional tests to determine if the lymphocyte count is harmless and temporary or if it signals a more serious underlying issue, such as blood cancer or a chronic infection. These tests may include a peripheral blood smear, a lymph node biopsy, a bone marrow biopsy or an IgE level measurement. The latter tests the level of a specific antibody concentrated within the blood.