Download 11.4: Immunity Healing and Protection Against Disease Recall that

11.4: Immunity
Healing and Protection Against Disease
Recall that platelets are cell fragments that are produced in the
bone marrow which aid in clotting blood.
clotting- solidification of blood where a blood vessel has been injured
Remember fibrin gets produced to eventually form a scab.
The blood’s ability to clot is reduced in 2 ways: by not having enough
platelets or by having a vitamin K deficiency.
Immunity
Immune system- natural defences that the body has to fight against
pathogens and maintain homeostasis; includes WBCs and proteins.
Our immune system includes:
- bone marrow
- white blood cells (phagocytes and lymphocytes)
- lymphatic system tissues (lymph nodes, tonsils, spleen and thymus)
immunity which is the ability of our bodies to fight infection by
producing antibodies or cells to inactivate the foreign particles.
pathogens- viruses, bacteria and other microbes (fungus and
protozoans) which cause disease; we are exposed to these every
day in the food we eat, water we drink and air we breathe.

Most microbes cause little or no damage to humans; many are
involved in symbiotic relationships (i.e. E. Coli in wall of large
intestine that helps human absorb nutrients.
Defending against pathogens...2 groups of defense; 3 lines of defense:
Non-specific defences- protect against variety of pathogens; protect the
body from all pathogens in the same way; effectiveness doesn’t depend
upon previous exposure.
1. First-Line Defenses- physical and chemical barriers like skin
(unbroken), sweat, tears, saliva, cell membranes, mucus, stomach
acid and urine
2. Second-Line Defenses- activated when pathogen gets by first-line
defenses and starts infection
Certain WBCs secrete a chemical called histamine which
causes the area to become swollen, hot, painful and red (an
inflammatory response). Histamine increases the flow of blood to the
wound and allows more exchange in the capillaries so other white blood
cells can attack the germs. Macrophages are giant white blood cells
that destroy and engulf large amounts of bacteria by phagocytosis.
This inflammation will cause fever to develop which will destroy some
germs. Neutrophils & monocytes are other WBCs that attack bacteria
using phagocytosis. Natural killer cells are WBCs which attack
cancerous or viral-infected cells as well.
Specific immune system- variety of cells that recognize foreign
substances and act to neutralize or destroy them; develops over time in
each individual depending upon which diseases a person is exposed to.
3. Third-line defense- activated when pathogen gets by first- and
second-line defenses and into the bloodstream. The last line of defense
is our immune system which recognizes, attacks, destroys and
remembers each kind of pathogen by producing antibodies which bind to
the pathogen and inactivate it. This line of defense is specific because
our immune system produces antibodies which are specific to every
different type of pathogen.
When our bodies recognize foreign cells or particles, they produce
antibodies or cells which bind to foreign substances and inactivate them.
This is called an immune response.
Antigens- foreign chemicals with large molecules on their surface
(proteins or toxins) which enter a cell and cause an immune
response
White blood cells will attack antigens:
lymphocytes- white blood cells designed to destroy specific antigens.
There are 2 types: B cells and T cells and both are produced in the
bone marrow and when they are mature they are released into the
circulatory and lymphatic systems.
B cells- remain in bone marrow
T cells- mature in thymus gland
There are 2 types of immune responses:
Primary immune response- body’s initial response to an antigen; does
not produce measurable amounts of antibodies during first 5 days
after exposure, but amts. rise gradually over next 10-15 days (fig.
11.28 p. 384)
Secondary immune response- rapid response by immune system when
it is exposed to an antigen a second time; high levels of antibodies
produced within 1-2 days
Both of these responses involve 2 types of reactions:
antigen enters body
↓
antigen gets ingested by macrophages;
antigen’s form is shown on cell membrane of macrophage
↓
Cellular Immunity
Antibody Immunity
T-cell recognizes antigen
B cell recognizes antigen
helper T cell recognizes antigen shown on macrophage
helper T stimulates T cell
to  forming killer T’s
and memory T’s
↓
killer T’s bind to virusinfected cells
↓
suppressor T’s release substances
to shut down killer T’s
when foreign cells under control
↓
if antigen re-enters, memory T’s
 producing new killer T’s
(secondary immune response)
helper T stimulates B cell
to  forming plasma cells
and memory B’s
↓
plasma cells produce antibodies
that bind to antigen (antigenantibody complex)
↓
suppressor T’s release substances
to shut down plasma cells
when foreign cells under control
↓
if antigen re-enters, memory B’s
 producing new plasma cells
(secondary immune response)
There are 2 types of immunity:
active immunity- body produces its own antibodies or killer T’s to fight
antigen; may develop from having had a disease (i.e. chicken pox)
or by vaccinations
passive immunity- “borrowed”; person is given antibodies via blood
from another person or animal; very fast, but temporary immunity
because after about 1 mth., body destroys antibodies (i.e. baby in
womb and breastfeeding)
Disorders of the Immune System
Allergy- rapid overreaction of immune system to an antigen which is not
usually harmful. There are 2 types:
- immediate (acute)- most common, occurs within seconds of
exposure & usually disappears in 30 minutes
- delayed
Some common allergens (or allergy-causing antigens) include: hay
fever (pollen), dust mites, insect stings, foods, pet dander.
Symptoms may include: runny nose, swollen eyes, coughing,
sneezing and rash. These symptoms result from the release of histamine
at the reaction site. Histamines are chemicals which increase
permeability of blood vessels; these cause an immune response (redness,
swelling). The effects of histamine can be counteracted using drugs
known as antihistamines.
Autoimmune diseases- a person’s immune system fails to recognize
body cells as “self” and produces antibodies against them. Examples
include: juvenile diabetes, rheumatoid arthritis, multiple sclerosis and
lupus. These autoimmune diseases can be inherited or can be caused by
viral or bacterial infections.
Cancer- disease in which cells multiply out of control. Cancer
cells probably form in our bodies all the time, but in healthy people T
cells destroy them.