The body’s natural defense
Against pathogenic
organisms
Nonspecific Defense Against a Pathogen –
Physical and Chemical Barriers
Salivary glands
skin
Eyelashes and eyebrows
tears
Stomach acid
mucus
Non-barrier, nonspecific
defenses
Inflammation turns
red from increased
blood flow to
damaged area
Swelling indicates the body
fever is sending more blood and
lymph to the affected area Infected cut –
to help correct the injury wbc battled
or fight the pathogen bacteria –
creates pus
Phagocytes - WBC (white blood cells)
Eat pathogens
Alert other
immune
system cells
that a
pathogen is
present
The Lymphatic System –
series of vessels carrying lymph and
phagocytes
Natural Killer Cells – WBC that
kill virus-infected cells
This target cell then dies
along with the viruses inside
it!
Interferons – small proteins that
cause normal, uninfected cells to
produce antiviral compounds that
interfere with viral replication;
they also stimulate macrophages
and NK into action.
Antigen-Antibody
Relationship
A foreign An ANTIBODY is
substance that produced in response
causes the to detection of a
production of an foreign substance
antibody to like the proteins on a
destroy it is virus or bacteria
called an ANTIGEN cell.
Specific Cellular Defense
B-cell eats pathogen,
breaks it apart, and
displays its proteins on
the surface of the B
cell.
Helper T cell, plasma
cell, and memory B
cells then are involved
in the antibody
response and
remembering it for the
next time.
1. Macrophage (white blood cell)
consumes a virus.
virus
macrophage
2. Macrophage digests virus and
displays viral antigens on its
surface
Antigen
3. One helper T cell recognizes
the antigen and binds to the
macrophage
Helper t cell
4. Chemicals (interleukin-1 and tumor necrosis
factor), made by the macrophage and others
(interleukin-2 and gamma interferon) made by the
T cell, allow intercellular communication
5. These chemicals instruct other helper
T cells and killer T cells to multiply.
The B cells multiply and produce
antibodies.
Killer t cell antibody
B cell
Helper t cell
6. Killer T cells destroy cells that have
been infected by the virus (and
unfortunately some uninfected cells, too)
Killer t cell
7. Antibodies released by B cells binds to
antigens on viruses – this makes it easier for
macrophages to eat the viruses and helps
destroy the viruses themselves.
8. When infection is controlled, suppressor T
cells stop the reaction. Memory cells remain
to respond quickly if same virus attacks again
Memory
b cell
Suppressor t cells
Memory cell
Allergies – the immune
system makes a mistake!
• Triggered by noninfectious agents such as
pollen or pet dander
• Causes an inflammatory response that could
be runny nose, sneezing, wheezing, hives,
etc.
• Can be developed after years of exposure to
the allergen – the body seems to reach a
critical exposure level.
The End