10/6/2001
Every minute, millions of "petrol" traveling in the bloodstream come out of our blood vessels, white blood cells that act like petrol
A team of Israeli researchers who used a sophisticated electron microscope, has now provided new information about the miraculous process of white blood cell migration, the immune system - on their way to attacked tissues.
Every minute, like in a "patrol", millions of white blood cells come out of our blood vessels, pass by "crossing stations" (lymph nodes), look for signs of enemy penetration - pollutants and causes of disease and inflammation - in order to attack them. The cells that do not recognize enemies - return to the blood.
In the study, led by Dr. Ronan Alon from the Department of Immunology at the Weizmann Institute and with the participation of Dr. Vera Shinder (electron microscopy), and their teams, published today in the scientific journal "Nature Immunology", the entire process is described.
When leaving the blood vessel wall, the white cells recognize molecules that can be called "stop signs". They are displayed on the inner side facing the blood, in the cell wall membranes of the blood vessels. Some of them function as troop launchers in a selected military unit: they point to a specific target, very specific cells, to a unique mission, in the right dose, at the right time and place.
In the first stage of cell migration, they roll on the inner wall, stop and unfold (ie:
flattened and stuck to the wall). Then they are pushed through a kind of narrow passage that forms between two wall cells
Close - and thus they go outside the blood vessels.
But this efficient mechanism is also abused by cancer cells. These migrate in the bloodstream to form cancerous metastases. They learned the "language of signs" that manages the migration process and through which they pile up on the body, infiltrate the tissues to start a destructive process and obscure traces. They force changes in the wall cells, so that they do not alert the cells of the immune system to attack them.
Tissue cells where, for example, inflammation occurs, signal the immune system and call it for help. The migrating cells are required to overcome the force exerted on them by the constant flow of blood.
It threatens to dislodge from their hold on the walls of the blood vessels and sweep them away in the current.
The signaling molecules - the chemokines - penetrate the wall cells in the blood vessels, presenting themselves on the cell membranes facing inward. They are used as stop signs in the migration process. the cells
The wanderers cling to them. However, the chemokines are also used as cell carriers, coming from the tissues
to the blood vessels.
The series of signals involved in this process depends on the ability of the migrating cells to sense the blood flow near where they exited the blood vessels, on their way to nearby tissue. When there is no flow, the migrating cells stop and adhere to the chemokines. This prevents them from taking the last, decisive step. They stay in the blood vessels, do not reach the tissues to fulfill their role - just flow with the blood, on.
A.D.M
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