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There are three types of lymphocytes in the blood and lymph. B lymphocytes, responsible for the production of specific antibodies (acquired immunity); T lymphocytes, which help distinguish foreign antigens from those specific to the body; and NK (natural killer) lymphocytes capable of destroying cancer cells or cells infected with viruses. The test provides the total for the three subclasses of lymphocyte as a number per litre of blood (lymphocyte #) and as a fraction of the total white blood cells (lymphocyte ratio). Results must be interpreted in light of clinical observations, other results from the current blood count, and variations in results over time.

A high number or ratio of lymphocytes (lymphocytosis) is found in acute viral infections (hepatitis, chicken pox, rubella, etc.) and some bacterial infections (tuberculosis, pertussis/whooping cough, etc.). Lymphocytosis is also found in lymphocytic leukemia and lymphoma.

A reduced number or ratio of lymphocytes (lymphopenia or lymphocytopenia) is found in autoimmune diseases (lupus, rheumatoid arthritis, etc.), certain infections (HIV, tuberculosis, hepatitis, influenza), bone marrow disorders (caused by chemotherapy or radiotherapy, for example) and immune deficiencies like AIDS and certain congenital immunodeficiencies.

Term of the Week

Creatine Kinase MM (CK-MM)

CK (creatine kinase) is an enzyme (protein) found in several tissues, including muscles and the heart. Depending on the tissue, different forms of CK are present: CK-MM is primarily present in skeletal muscles, CK-MB represents 30% of CK from the heart, while CK-BB comes from the brain and smooth muscle, such as the intestinal walls. Atypical forms of CK (macro CK1 and macro CK2) can also be present. CK electrophoresis is most useful when muscular or cardiac disease does not seem to be responsible for the increased level of total CK.