Page 305 - ABCTE Study Guide_Neat

Phagocytes

These are white blood cells that can ingest and kill foreign cells or pathogens in the body through
phagocytosis. By recognizing antigens on invading cells as foreign, phagocytes and other immune
response cells attack these cells while ignoring body cells.

When these immune cells are unable to tell the difference between native and foreign cells, autoimmune
diseases, such as rheumatoid arthritis, can occur. This cell recognition and attack mechanism must be
suppressed when organ transplants are made.

Complement Proteins

These circulate in the bloodstream and help kill invading pathogens by promoting lysis, or disintegration,
of the plasma membrane or by attracting phagocytes to a site of injury or invasion. The inflammatory
response is the result of the many actions the body takes to battle an invasion.

Specific Defenses

When the nonspecific defenses are not enough to win out over an infection, additional white blood cells
(B-cells, T-cells, and natural killer cells) may be called upon. These cells are the foundation of the body’s
immune system and can launch very targeted attacks on invading organisms, as well as develop immunity
from future infections.

When the specific immune response is required, two major types occur:

• Antibody-mediated
Lymphocytes called B cells are produced in the antibodies for a specific type of antigen.
When a given B cell recognizes an invader with the antigens capable of binding to the B cell’s
antibodies, it will bind and will essentially “tag” the invading cell for destruction by means
such as phagocytosis or lysis.
• Cell-mediated response
T cells called "killer T cells" develop in the bone marrow and move eventually into the thymus
gland to produce more of their own kind. These cells, along with what are known as NK
ornatural killer cells, directly attack and kill cells that are already infected—mostly by
viruses. These cells must be controlled when organs are donated.
• Controlling-immune Response
Helper T cells turn on the immune-system response and promote the production of both B
cells and killer T cells. Suppressor T cells are controller lymphocytes, which slow down or
prevent immune responses. Memory cells are portions of the B and T cell populations
produced when a specific invader is recognized. These are essentially reserve troops
programmed to attack a specific invader but not used in the initial attack.

Compromised Immune Systems

AIDS, or Acquired Immune Deficiency Syndrome, is so difficult to combat because it is a virus that
invades the very T cells which would normally be used to combat it. Hence a person with HIV can have an
extremely compromised immune response and can be very susceptible to other types of infections or
cancer, which most often prove fatal.

Cancer cells are cells that have lost control over cell division and that may eventually kill surrounding
tissues. These cells can be attacked by killer T cells but often are not recognized by the body’s immune
system. The cancer cells may not have surface markers that are different than normal body cells.