word "white blood cells" literally translates as "white cells".In fact, they are not white but transparent.Unlike erythrocytes they have a nucleus.They surpass erythrocytes and size.This is the major blood elements, their size ranges from 8 to 20 microns.

Origin leukocytes

Amphibians leukocytes is much more than a man.This is because not only leukocytes amphibians compete with pathogens, but also are involved in digestion.This fact allows us to trace the evolutionary history of leukocytes.

At the dawn of the existence of multicellular organisms there was no question of organs and tissues, even, were the only group with respect to the di
fferentiated cells.All were able to capture and digest food particles.Among them were the cells resembling amoebas that have been able to move in search of food.At the same time they are captured and foreign objects trapped in the body.

That these wandering cells and leukocytes occurred.As the differentiation of cells forming tissues, organs and systems are no longer needed for their participation in digestion, and they are fully focused on fulfilling the protective function.

Not surprisingly, the white blood cells began to form elements of blood.Blood rich in oxygen and nutrients, which makes it attractive to microorganisms.They will inevitably fall into the blood as it passes through the areas of the body, taking a substance from the outside world - the respiratory and digestive system.

However, not only leukocytes present in the blood.They can go deep into the tissue to reach the surface of the mucous membranes.

Species leukocytes

At penetration into the body of disease-causing microbes and other foreign objects first blow assume phagocytes.Among white blood cells, these cells retain much of the "memory" of his "digestive" evolutionary past.They destroy enemies, consuming them.A macrophage is capable of destroying up to 20 so germs.When he dies, poisoned by their toxins, but release substances that attract other phagocytes.They are concentrated in the site of infection and die one by one, absorbing foreign microorganisms, so it is formed pus.

fight against pathogens - the main, but not sole task of phagocytes.They absorb the dead and damaged cells.

If a disease-causing microbes, despite the efforts of phagocytes, were able to break through into the body, with them fighting another kind of white blood cells - lymphocytes.Their task - to produce antibodies, special proteins that are essential for recognizing foreign objects (antigens) and trigger a variety of immune mechanisms.

enemies leukocytes

leukocytes protects the body against pathogens, but there are viruses dangerous to themselves leukocytes.

One such virus - HIV.It affects a type of lymphocytes - T-lymphocytes.Their death deprives the immune system to recognize the possibility of infection.Figuratively speaking, "the state does not know what he was attacked."Such a body is little that can be done to defense.

Another virus infects white blood cells - a measles virus.Propagating within leukocytes, with them it penetrates into any tissue, in any organ, without encountering any resistance.Therefore, measles can give dangerous complications to any organ: lungs, middle ear, eyes, brain.Such complications can lead to severe disability and even death.

Under these zablevaniyah a paradoxical situation: a person has to protect its defenders.And if a vaccine against HIV infection does not exist yet, the vaccination against measles can and should be.