StemCell Therapy

Recognition.The antigen or cell is recognized as nonself. To differentiate self from nonself, unique molecules on the plasma membrane of cells called themajor histocompatibility complex (MHC)are used as a means of identification.

Lymphocyte selection.The primary defending cells of the immune system are certain white blood cells called lymphocytes. The immune system potentially possesses billions of lymphocytes, each equipped to target a different antigen. When an antigen, or nonself cell, binds to a lymphocyte, the lymphocyte proliferates, producing numerous daughter cells, all identical copies of the parent cell. This process is calledclonal selectionbecause the lymphocyte to which the antigen effectively binds is selected and subsequently reproduces to make clones, or identical copies, of itself.

Lymphocyte activation.The binding of an antigen or foreign cell to a lymphocyte may activate the lymphocyte and initiate proliferation. In most cases, however, a costimulator is required before proliferation begins. Costimulators may be chemicals or other cells.

Destruction of the foreign substance.Lymphocytes and antibodies destroy or immobilize the foreign substance. Nonspecific defense mechanisms (phagocytes, NK cells) help eliminate the invader.

Link:
Specific Defense (The Immune System) - Written by Teachers

This entry was posted on October 16, 2017 at 12:50 pm and is filed under Immune System. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. |