Biomedical Engineering Reference
In-Depth Information
resulting in the formation of auto antibodies against the myelin sheaths leading to destruction of
the insulating layer surrounding neurons in the brain and spinal cord. When the myelin sheath is
destroyed, nerve messages are sent less efi ciently. Patches of scar tissue, called plaques, form over
the affected areas, further disrupting nerve communication. The symptoms of MS occur when the
brain and spinal cord nerves no longer communicate properly with other parts of the body. MS
causes a wide variety of symptoms and can affect vision, balance, strength, sensation, coordination,
and bodily functions.
RA is a chronic autoimmune disease that causes inl ammation and deformity of the joints. In
RA, the underlying event that promotes RA in a person is unknown. Given the known genetic fac-
tors involved in RA, some researchers have suggested that an outside event occurs that triggers the
disease cycle in a person with a particular genetic proi le. The body's normal response to such an
organism is to produce cells that can attack and kill the organism, protecting the body from the
foreign invader. In an autoimmune disease like RA, this immune cycle spins out of control. The
body produces misdirected immune cells, which accidentally identify parts of the person's body as
foreign. These immune cells then produce a variety of chemicals that injure and destroy parts of the
body. Autoantibodies (antibodies against self protein) are observed in 80% of the patients.
IDMM and MS are examples of organ-specii c autoimmune diseases as only one organ is affected
whereas RA is an example of a systemic autoimmune disease involving many tissues.
22.3.2 I
NFLAMMATION
An inl ammation is a manifestation of the immune system's response to invading organisms or
substances. At the site of the infection, there are a number of physiological changes that take place
to assist the destruction of the invaders. These include
•
Increased blood l ow to the area to maximize the number of leukocytes that can get to the
infection site.
A thinning of the cells in local blood capillary walls (endothelial cells) to allow the
•
leukocytes to squeeze through.
An increase in local temperature that has an antibiotic effect.
•
•
A large number of immune system signaling molecules (chemokines) are released by
leukocytes to coordinate the immune response and to call more leukocytes to the site.
Once the invader has been dealt with, the body terminates the immune response by killing off
the leukocytes in the locality. This is done by depriving them of nutrients (necrosis) and by
apoptosis.
22.3.3 C
ANCER
I
MMUNOLOGY
Recently, we have learned that the immune system may play a central role in protecting the body
against cancer and in combating cancer that has already developed. This latter role is not well
understood, but there is evidence that in many cancer patients the immune system slows down the
growth and spread of tumors. On the other hand, when the immune system is weakened by old age
or environmental factors, it can be more easily overwhelmed by cancerous cells.
One immediate goal of research in cancer immunology is the development of methods to harness
and enhance the body's natural tendency to defend itself against malignant tumors. Immunotherapy
represents a new and powerful weapon in the arsenal of anticancer treatments. Immunotherapies
involving certain cytokines or antibodies that recognize cancer cells specii cally and deplete the
cells via ADCC have now become part of the standard cancer treatment.
