Natural killer cells
Natural killer cells or NK cells fulfill a similar role as the T-killer cells, but unlike the other lymphocytes, they do not belong to the adaptive but to the innate immune system. This means they are permanently functional without having to be activated beforehand. However, their reaction is difficult to regulate. Nevertheless, they belong to the lymphocytes, since they develop from the same precursor cells.
Standard values of lymphocytes
The concentration of lymphocytes fluctuates throughout the day and depends on the time of day, stress, physical exertion and other factors. One only speaks of a pathological increase if the lymphocytes are above the limit values. To determine the number of lymphocytes, a differential blood count is required, which is part of the large blood count.
The proportion of lymphocytes in the total leukocyte count (leukocyte=white blood cell) should be between 25 and 40%, which corresponds to a concentration of 1. 500-5. 000/μl. If the value is higher than this, one speaks of lymphocytosis, if it is lower, one speaks of lymphocytopenia (also lymphopenia). In small children the concentration of leukocytes can be much higher and the proportion of lymphocytes can be up to 50%.
What can be the cause if the lymphocytes are elevated?
In most cases, an increased number of lymphocytes (=lymphocytosis) indicates a viral infection, since lymphocytes are particularly suitable for fighting it. Basically, all virus infections are associated with at least a slightly increased lymphocyte concentration. In addition, certain bacterial infections such as pertussis (whooping cough, whooping cough), tuberculosis (consumption), syphilis, typhoid fever (enteric fever, parietal fever) or brucellosis (Mediterranean fever, Malta fever) also trigger a characteristic increase in lymphocytes.
The number of lymphocytes remains increased even in chronic, i.e. long-lasting courses. Other parasites such as Toxoplasma gondii can also lead to a short-term increase in lymphocytes. However, there are also inflammatory diseases without infection that lead to an increased number of lymphocytes, such as the intestinal diseases Crohn’s disease and ulcerative colitis, as well as autoimmune diseases such as Graves’ disease, in which the lymphocytes produce antibodies against thyroid cells, which excites them excessively, which in turn disturbs the hormonal balance.
Sarcoidosis (Boeck’s disease), a special form of inflammation that particularly frequently affects the lungs, can also lead to an increase in the number of lymphocytes. However, a disturbed balance of thyroid hormones, as in hyperthyroidism or Addison’s disease (primary adrenal insufficiency), can also lead to an increase in lymphocyte count. This may also be of interest to you: Addison’s diseaseA particularly severe lymphocytosis can occur in certain malignancies, i.e. malignant tumor cells: In chronic lymphatic leukemia (ALL), it is the precursor cells of the lymphocytes that have developed into cancer cells due to mutations.
This is the most common form of leukemia in the western world. Since it occurs particularly frequently around the age of 50, it is also called “old-age leukemia“. Acute lymphatic leukemia also develops from lymphocyte precursor cells, but is usually accompanied by rapid degeneration of the bone marrow, which can lead to anemia because the other blood cells cannot develop properly.
As a result, in some cases no change or even a reduction in total leukocytes can be observed. The abnormally increased number of lymphocytes only becomes apparent in the differential blood count. Since the mutated lymphocytes are generally functionless in both diseases, a reduced performance of the immune system can be assumed despite the increased number.Furthermore, other malignant tumors affecting other cells of the lymphatic system can trigger lymphocytosis, such as Hodgkin’s lymphoma (Hodgkin’s disease, lymphogranulomatosis, lymphogranuloma), but also certain non-Hodgkin’s lymphomas.
