NURSING BULLETS: Immune System

• The immune response involves white blood cells called lymphocytes. The most important are B and T cells.

• Each B and T cell is programmed to recognize and respond to one specific protein, called an antigen. Different antigens are present on cell membranes. When lymphocytes encounter their specific antigens, they bind in a “lock and key” manner and destroy the cell.

• B cells respond by transforming into antibody-secreting cells. Their antibody binds to the antigen, causing its destruction. Some B cells remain in circulation, carrying the memory of that antigen.

• T cells respond by transforming into helper, cytotoxic, or memory cells.

• T helper cells help B cells change into antibody secreting cells. Without helper T cells presenting antigens to a B cell, the B cell does not respond.

• Cytotoxic T cells act alone, without B cells. The cells destroyed by cytotoxic T cells are those infected by a virus or a cancer cell changed by mutation.

• T cells can become memory cells and remain in the circulation for years, ready to respond again if their antigen should appear.
• The first time B and T cells are exposed to a specific antigen, the response takes weeks. If re-exposure occurs, B and T memory cells respond immediately to destroy the invader.

• Normally, the immune response is well controlled. If not, autoimmune disease may occur, and self-antigens may be attacked.