and cells from transplant donors (human or animal). The immune system pre-
vents an invasion from attacking internal organs and, if that fails, the immune
system neutralizes, destroys, and eliminates any non-self proteins and cells,
including microorganisms.
Non-self proteins and cells also include self cells (the body’s own cells) that
have become infected or debilitated. One example is malignant transforma-
tion that changes healthy cells into cancer cells. The ability of the immune
system to differentiate between the body’s own cells and non-self cells is
called self-tolerance.
The immune system is able to recognize self-cells by using unique proteins
that are on the surface of all self-cells. Think of these proteins as an identifica-
tion code. Foreign cells have a different identification code. These are called
antigens and stimulate the immune response of a host.
When bacteria invade your body, your immune system detects the bacteria’s
surface protein as not being a self-cell. This triggers your immune system to
launch an attack against the bacteria.
The immune system originates in the bone marrow. Mature immune system
cells are released from the bone marrow into the bloodstream where they circu-
late throughout the body looking for invaders.
There are three processes necessary for immunity: inflammation, antibody-
mediated immunity (humoral immunity), and cell-mediated immunity (CMI).INFLAMMATION
This is discussed in detail in Chapter 12.ANTIBODY-MEDIATED IMMUNITY
Antibody-mediated immunity occurs when the immune system produces antibod-
ies that neutralize, eliminate, or destroy an antigen (foreign protein). Antibodies
are produced by B lymphocytes. The body must be exposed to sufficient amounts
of an antigen before the immune system produces an antibody to combat the
antigen. Patients can be given vaccinations that stimulate the immune system
to generate antibodies before the microorganism actually invades the body. In
this way, the antibodies already exist and can attack at the first sign of the
microorganism.(^316) CHAPTER 17 Immunologic Agents