Lymphocytes are produced by lymphoid organs and are a class of cells that produce and transport antibodies and defend against viral infections. They are divided into three main categories: T cells, B cells and natural killer (NK) cells, and are important cellular components of the body’s immune response function. Low lymphocytes include both absolute and relative decreases.
Any of the various causes that lead to a significant increase in neutrophils can lead to a relative decrease in lymphocytes, a decrease in the lymphocyte ratio, but not a decrease in absolute numbers.
Absolute decrease in lymphocytes is commonly seen in the following causes: lymphocytopenia during recovery from influenza; HIV infection, which selectively destroys CD4+ cells leading to a significant decrease in CD4+ cells and an inverted CD4+/CD8+ ratio; tuberculosis, where early lymphocytopenia CD4+ cells are significantly reduced and lymphocytes can return to normal if treatment is effective; alkylating agents (cyclophosphamide etc.) can cause a significant decrease in leukocytes, accompanied by a significant decrease in lymphocytes, and the decrease in lymphocytes can persist for several years after stopping treatment; radiation therapy can destroy lymphocytes, with each low-dose radiation therapy producing more destruction than 2 high-dose radiation therapies per week; immune diseases such as systemic lupus erythematosus, rheumatoid arthritis, mixed connective tissue disease, and polymyositis, due to antibodies producing anti-lymphocyte antibodies, resulting in Lymphocyte destruction and reduction, and the degree of reduction correlates with the titer of the antibody; congenital immunodeficiencies, such as various types of severe combined immunodeficiency, ataxia capillaris, malnutrition, or zinc deficiency, can cause lymphocytopenia to varying degrees. Certain drugs can also cause lymphopenia, such as menadione, nitrogen mustard phenylbutyrate, cortisone, epinephrine, lithium, nicotinic acid, steroids, etc.
Therefore, there are many causes of low lymphocytes, and the specific diagnosis needs to be combined with clinical symptoms and other relevant laboratory tests.