Download Immune System Lecture File

Infectious Diseases and the
Immune System
“What doesn’t kill you makes you
stronger.”
Types of pathogens
1. Bacteria: single cell organism
World's Dirtiest Man
2. Virus: not alive, one or more molecules of
DNA or RNA enclosed in a protein capsule.
3. Protists: usually single celled organisms
without specialized tissues. Giardia
4. Fungi: ringworm, yeasts
5. Invertebrates: parasitic worms
Modes of Disease Transmission
1. Air: tuberculosis, cold
2. Food: Salmonella, E. coli, botulism
3. Water: Giardia
4. Person-to-person: (cold, hepatitis, HIV)
5. Vectors - animal bites/scratches/burrowing:
(malaria/lyme disease)
Koch’s Postulates
1. The suspected
pathogen must
occur in the body
of an animal with
the disease but
NOT in the body of
a healthy animal.
Koch’s Postulates
2. The suspected
pathogen should
be isolated,
identified, and
grown in a
laboratory
culture.
Koch’s Postulates
3. If a healthy animal
is inoculated with
the cultured
pathogen, it should
develop the
disease.
Koch’s Postulates
4. If the pathogen from
the second animal is
isolated and grown in
the lab, and identified
as the same one
isolated from the first
animal, that confirms
this pathogen as the
cause of this particular
disease.
Nonspecific Defenses
• Protect against any pathogen regardless of
identity
First Line of Defense
• Physical barriers – skin, mucous membranes
• Skin
tough, keratin-filled cells
Secretes oils & waxes (sebum) toxic to bacteria & fungi
Sweat (and tears) contains lysozyme, destroys cell walls
of bacteria
very effective if not broken
• Line all interior surfaces
exposed to environment
 respiratory system
(works w/cilia)
 digestive system
 urethra
 Vagina
• Sticky mucus traps
pathogens
• Stomach acid &
enzymes destroy many
pathogens
Mucous
Membranes
Second Line of Defense
Second Line of Defense
1. Inflammatory response – redness, swelling, warmth, pain
a) Pathogens stimulate special WBC called mast cells to
release histamine.
b) Histamine dilates blood vessels & increases blood flow
to the area. May also increase mucous production.
c) Histamine also increases permeability of capillaries to
fluids & white blood cells (WBC), accumulate as pus.
② White Blood Cells –
Second Line of Defense
WBCs involved in inflammatory
response are called phagocytes
(phage = “to eat”). Phagocytosis =
eats cells.
a) Neutrophils: 50-70% of all WBCs –
each engulfs & destroys a pathogen,
neutrophil also dies in the process.
b) Macrophages: travel in blood,
lymph, intercellular fluids, engulf &
destroys pathogens, worn out cells,
& cell debris. Long-lived.
c) Natural Killer Cells – seek & destroy
cancer cells and cells invaded by
pathogens (viruses). Punctures cell
membrane, water rushes in, cell
bursts.
Second Line of Defense
3) Nonspecific Immune Proteins
a) Complement system – 20 proteins that
enhance (“complement”) the ability of
antibodies & phagocytes to clear
pathogens from body. Activates MAC.
b) MAC – membrane attack complex – forms
channels across cell membranes of
pathogens, causes cell lysis (bursting) and
death.
Nonspecific Immune Proteins
C) Interferon – inhibit (“interfered” with)
reproduction of viruses. Released by infected
cells, stimulates nearby cells to make enzyme
that inhibits synthesis of viral proteins. Buys
time for specific immune response.
Second Lind of Defense
④Fever – body temp.
(controlled by
hypothalmus in brain)
above 98.6o F (37o C).
Body attempts to “cook”
proteins of pathogens
without cooking its own.
Fever above 103o F is
dangerous, over 105o F
can be fatal.
Third Line of Defense
• Specific Immunity – immune system targets
specific pathogens
• Pathogens identified by the antigens on their
surfaces.
Organs of the Immune System
•
•
•
•
•
•
•
Red bone marrow
Thymus
Lymph nodes
Spleen
Tonsils
Adenoid
Peyer’s patches
Organs of
the Immune
System
Red bone marrow
makes stem cells
that differentiate
to form
neutrophils, macrophages, natural killer cells, and
lymphocytes.
Thymus – some immature
lymphocytes migrate to
the thymus and mature
there. These are called
T cells. There are 3 kinds:
• Helper T cells
• Suppressor T cells
• Cytotoxic T cells
Other lymphocytes remain
in the bone marrow to
mature. These are B cells.
Organs of the
Immune System
Organs of the Immune System
Lymph nodes –
• populated by
lymphocytes and
macrophages
• filter lymph looking
for foreign
antigens, worn out
cells, or cellular
debris
Spleen –
circulatory
system’s
counterpart to
lymph nodes.
• Located behind
stomach
• Filters
pathogens from
blood.
Organs of the
Immune System
• Adenoids – located
on either side of the
throat near the roof
of the mouth
• Tonsils - located
below & behind soft
palate.
• Both are cluster of
lymphatic tissue
that intercept
inhaled germs and
dust & initiate B & T
cell responses.
Organs of the
Immune System
Organs of the Immune System
Peyer’s Patches –
• Lymphatic tissue
embedded in the
walls of the small
intestine.
• intercept pathogens
not destroyed by the
stomach.
Third Line of Defense – Specific
Immunity, Primary Immune Response
How it works:
1) Macrophage encounters &
engulfs pathogen.
2) Macrophage displays antigens
of pathogen on its own cell
membrane.
3) Macrophage connects with a
Helper T Cell with a receptor
matching the antigen. This
stimulates the Macrophage to
produce Interleukin-1.
Third Line of Defense – Specific
Immunity, Primary Immune Response
4) Interleukin-1 stimulates Helper T cell to
produce Interleukin-2.
5) Interleukin-2 stimulates four different
populations of cells:
a. Helper T Cell itself, to divide into clones.
b. Cytotoxic T Cells
c. B Cells
d. Suppressor T Cells
Third Line of Defense – Specific
Immunity, Primary Immune Response
Cytotoxic T Cells:
• Stimulated
• Rapidly divide into army of
cells programmed to find and
destroy the specific pathogen,
infected cells, or cancer cells of
the pathogen first encountered
by the macrophage.
• Recognize infected cells by
viral proteins on the cell
surface or antigens on cancer
cells.
• This is Cell-Mediated Immune
Response.
Third Line of Defense – Specific
Immunity, Primary Immune Response
B Cells:
• stimulated
• divide rapidly
• differentiate into
Plasma Cells, which
make antibodies
specific to pathogen
first encountered by
macrophage.
• Called Humoral
Immune Response.
Third Line of Defense – Specific
Immunity, Primary Immune Response
Antibodies
• Y-shaped proteins with
receptors specific for
antigen of pathogen first
encountered by
macrophage.
• Antibodies bind to
pathogen, flag it for
destruction by nonspecific
WBCs or Cytotoxic T Cells,
and may inhibit viruses
from infecting cells.
Third Line of Defense – Specific
Immunity, Primary Immune Response
Suppressor T Cells:
• Once stimulated, begin
dividing, but much
slower than Cytotoxic T
Cells and B Cells.
• Function: to shut down
cell division of B Cells.
• Delay gives the B Cells
time to proliferate
enough to deal with the
infection.
• MOST of the
Cytotoxic T Cells and
B Cells produced by
the Primary Immune
Response are
relatively short-lived.
• SOME are
programmed to live
much longer, remain
in body long after
first infection is
eliminated. THESE
are called Memory T
Cells and Memory B
Cells.
Secondary
Immune
Response
• Memory T & B Cells patrol
circulatory and lymphatic
systems & organs of
immune system for many
years, often for life.
Memory T & B cells =
immunity to that
pathogen.
• IF they ever encounter
same pathogen again,
response is RAPID and
STRONG. They
immediately begin dividing
to quickly accomplish their
jobs.
• Secondary immune
response is so fast and
efficient that person often
does not even know he/she
is infected.
Secondary Immune
Response
Immunity
• Immunity can be monitored by checking the
level of antibodies in the blood
• This level is known as the antibody titer.
• immune response to
harmless antigens
(dust, pollen, etc.) –
called allergens
• symptoms – cells in
contact with antigen
release histamine,
causes runny nose,
watery eyes, sneezing,
itching to expel antigen
from body
• severe allergic
reactions can include
anaphylactic shock –
life threatening
Allergies
Autoimmune Diseases
Your immune system attacks your own cells.
a. Multiple sclerosis – attacks nervous system
b. Type 1 diabetes – attacks insulin-producing
cells of pancreas
c. Lupus – attacks connective tissues
d. Rheumatoid arthritis – attacks joints, causes
inflammation
e. Graves disease – attacks thyroid
HIV & AIDS
• HIV attacks Helper T cells.
• Lowered levels of Helper T
cells are unable to initiate a
full primary immune
response.
• Individual dies of an
opportunistic infection, a
pathogen or cancer that a
healthy immune system
would have defeated easily.