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Immune System
Biology
Ms. Boehm
March 2014
What is the Immune System?
 The body’s defense system, which fights off pathogens
that cause disease- it keeps you healthy!
 Pathogen = a foreign substance that can cause disease
Bacteria, virus, etc.
st
1
Line of Defense
 All first line of defense is non-specific, meaning they don’t
distinguish among pathogens
 Skin: shields body from harmful invaders (Barrier)
1st Line of Defense
 Mucus & Cilia: (Barriers)
 Mucus traps foreign microbes & dust that are allowed in
through nasal hair
 hair-like structures (cilia) in the lungs sweep mucus
upward & out of system
st
1
Line of Defense
What’s the first thing you do when you cut
your finger?
 Saliva: contains chemicals that break down bacteria (Barrier)
1st Line of Defense
 Stomach Acid: swallowed bacteria is broken down by
strong acids in stomach (Barrier)
2nd Line of Defense
 The second line of defense is non-specific as well, but is now inside the
body/bloodstream
 White Blood Cells: if invaders do make it inside the body, WBC’s engulf & destroy them
 Also known as phagocytes or leukocytes
 Perform phagocytosis- cell eating
 Breakdown of bacteria occurs in lysosome
Video
2nd Line of Defense
 Another 2nd line of defense is the inflammatory response
 The chemical response is known as histamines

you have probably taken an antihistamine before
rd
3
Line of Defense
 The third line of defense is a specific, targeted attack on
pathogens
 Able to distinguish self vs. non-self invaders
 Has a role in immunity
Each antibody is specific to a certain antigen
Types of WBC’s
 Lymphocytes = originate in the bone marrow & travel
throughout lymphatic system to recognize specific
invaders
 B cells = programmed to make certain antibodies
 Develop in bone marrow
 T cells = responsible for attacking & destroying harmful
pathogens
 Develop in thymus gland
How do Antigens work?
 Antigens are proteins on the outside of a pathogen, unique to each
one
 identifies the pathogen as non-self and the body uses it for identification
and marks it for destruction
 Immune system responds by releasing Antibodies, which fit
onto the Antigens perfectly
 Antibodies: proteins that attach to specific antigens in the body (made by
WBC’s)
antibody
pathogen
antigen
What happens next?
 Once the Antibodies are attached to the antigen, it
triggers a macrophage to come along and engulf the
entire pathogen
antibody
pathogen
antigen
macrophage
(WBC)
Stop and Review
 What is the role of the immune system?
 Compare and contrast the 1st, 2nd and 3rd lines of
defense. How are they similar, how are they different?
 Define antigen and antibody. Relate the two terms to
each other.
 What type of organelle do you think a macrophage
must have a lot of?
Immunity
 Why is it impossible to get the same type of cold
twice?
 Your body has been exposed to the antigen
 You make antibodies that eventually destroy it
 The next time that same antigen tries to come
around, those same antibodies will destroy it
immediately
Immunity
 How do Vaccines work?
 Your body is injected with dead or weakened
version of the ________________.
Think the flu is no big deal?
 Think again…
 In 1918, a particularly
deadly strain of flu, called
the Spanish Influenza,
spread across the globe
 A form of H1N1 that is
present again today.
 It infected 20% of the
human population and killed
5%, which came out to be
about 100 million people
Immune Disorders
 Allergies
 When your immune system mistakes harmless
foreign particles (dust, pollen) as serious threats
 Immune system launches a response, which causes
sneezing, runny nose, & watery eyes
Immune Disorders
 Autoimmune diseases
 The immune system turns against itself
 The surface proteins on our own cells are viewed as
foreign and the body makes antibodies to destroy the
cells
 Not sure why the body turns against itself
 Examples:
 Rheumatoid arthritis, lupus, type I diabetes
Immune Disorders
 Acquired Immune Deficiency – AIDS
 Caused by Human Immunodeficiency Virus (HIV)
 Discovered in 1983
 Targets and kills T-cells
 Immune System is weakened
 HIV doesn’t kill you
 Common diseases that your body can no longer fight off can
become life-threatening
Immune Disorders
 Acquired Immune Deficiency – AIDS
 Transmitted through sexual contact, blood transfusions,
contaminated needles
 AIDS affects over 40 million people worldwidepeople