Lymphocyte
Lymphocyte , special group of white blood cells ; They are the blood cells that are involved in the body ‘s defense mechanisms and immune reactions .
Lymphocytes are a type of white blood cell that performs several functions in the immune system , including protection against bacteria , viruses , fungi and parasites . Lymphocytes typically make up 20 to 40% of the leukocytes (white blood cells) found in the blood.
Functions of lymphocytes
Lymphocytes participate in the fight against foreign microorganisms and tumors . They are also responsible for the phenomenon of rejection of transplanted organs .
The number of lymphocytes is usually above 1500 cells per microliter of blood (1.5 × 10 9 per liter) in adults and 3000 cells per microliter of blood (3 × 10 9 per liter) in children. A reduction in the number of lymphocytes may not cause a noticeable decrease in the total number of white blood cells. Since the lymphocytes are at a very low level, what is known as lymphopenia occurs . [1] [2]
Types of lymphocytes
There are three types of lymphocytes. All three types have important functions in the immune system:
- B lymphocytes(B cells). They represent between 10 and 20% of the total lymphocyte population, circulate in the blood and transform into antibody- producing plasmacytes in case of infection . They are responsible for humoral immunity. A low number of B lymphocytes can lead to a decrease in the number of plasma cells, which produce antibodies. Decreased antibody production can cause an increase in bacterial infections.
- T lymphocytes(T cells). People with too few T lymphocytes or too few natural killer cells have problems controlling certain infections, especially viral, parasitic, and fungal infections. Significant deficiencies in lymphocytes may lead to difficult-to-control infections, which can be fatal. T lymphocytes are further divided into two groups that perform different functions:
- Killer T lymphocytes (killer or suppressor cells) are activated by abnormal cells ( tumoror infected by viruses ); They attach to these cells and release toxic substances ( lymphokines ) to destroy them.
- T helper lymphocytes stimulate the activity of T killers and intervene in other varied aspects of the immune reaction. HIV (the virus responsible for AIDS ,which is acquired immunodeficiency syndrome), destroys these categories of lymphocytes and, therefore, weakens the immune system.
- NK cells(natural killer lymphocytes )
