White blood cells
These are leukocytes, they intervene in the defense of the organism from external aggressors. They represent only 0.2% of blood cells! There are several types:
- Polymorphonuclear cells or granulocytes : They are the most numerous (up to 70% of white blood cells). They circulate in the blood and only come out during inflammation to engulf foreign elements. We can distinguish neutrophils, the most numerous, acidophils and basophils (which form mast cells in connective tissues). Their duration is very short, at most a few days.
- Monocytes (2 to 8%): they circulate in the blood and practice phagocytosis. After only 3 days they differentiate into macrophages and pass into the tissues. Macrophages live for several months. They more especially “monitor” the mucous membranes that foreign elements have a better chance of penetrating.
- Lymphocytes
(25 to 30%): Depending on their place of maturation, a distinction is made between B lymphocytes and T lymphocytes. During an immune reaction, only B lymphocytes, which carry receptors for the antigens present, differentiate into plasma cells which secrete antibodies and, a small part, in memory B lymphocytes. T lymphocytes also circulate in the blood but also remain in the lymphoid organs. They have several functions, the main one being to trigger specific immune reactions to a particular antigen. Some specialize in cytokine production (auxiliary or helper T lymphocytes, or T4) while others specialize in antigen destruction (cytotoxic or effector T lymphocytes, or T8)
Lymphocytes are able to leave the blood to reach infected tissue. Their life span is a few months, except for memory lymphocytes, which can live up to 10 years!
NK cells are derived from T lymphocytes.
to know more
animal physiology : A real scientific work online! Currently not completed.
HematoVinci
: Blood cells in the presentation.blood cells : Lots of information on the figurative elements of blood.
