The document explains the immune system's role in defending the body through various defense mechanisms, including the first line (skin, sweat, tears, etc.), second line (phagocytosis and inflammatory response), and third line (specific immune response). It outlines key terminology such as antibodies, antigens, immunity, and vaccination, as well as types of immunity (passive and active) and related immune system disorders like hay fever and asthma. Additionally, it details the processes by which the body recognizes and responds to pathogens, emphasizing the importance of specialized cells and antibodies.

1. THE IMMUNE SYSTEM
Students should be able to:
Describe the role of the blood in defending the body
Explain how the principles of immunization are used to
control communicable disease

2. T E R M IN O L O G Y
• A N T I B I O T I C S : A drug used to treat infections
caused by bacteria and other microorganisms
(inhibits growth or destroys).
e.g. penicillin, streptomycin, tetracycline
• A N T I G E N : A toxin or other foreign substance
that induces an immune response in the body, esp.
the production of antibodies.
• A N T I B O D Y : A blood protein produced in
response to and counteracting a specific antigen

3. • I M M U N I T Y : The ability to resist a particular toxin
by the action of specific antibodies.
• I M M U N I Z A T I O N : the act of making immune
(especially by inoculation, i.e. taking a vaccine as a
precaution against contracting a disease).
• V A C C I N E : A substance used to stimulate the
production of antibodies and provide immunity against
one or several diseases, prepared from the causative
agent of a disease, its products, or a synthetic
substitute, treated to act as an antigen without
inducing the disease.

4. FIRST LINE OF DEFENSE
• Goal: to stop pathogens from entering the body
 Skin – acts as a barrier to invasion
 Sweat – has chemicals which can kill different
pathogens.
 Tears - have lysozyme which has powerful
digestive abilities that render antigens harmless.
 Saliva – also has lysozyme.
 Mucus - can trap pathogens, which are then
sneezed, coughed, washed away, or destroyed
by chemicals.
 Stomach Acid – destroys pathogens

5. SECOND LINE OF DEFENSE
• If a pathogen is able to get past the body's first
line of defense, and an infection starts, the body
can rely on it's second line of defense.
• First there is a non-specific response
(phagocytosis) followed by an INFLAMMATORY
RESPONSE.

6. • Phagocytosis =
ingestion + digestion
of pathogens.
• Phagocytic leucocytes
(macrophages) engulf
pathogens.

7. Inflammation causes:
ii.Redness - due to capillary dilation resulting in
increased blood flow
iii.Heat - due to capillary dilation resulting in
increased blood flow
iv.Swelling – due to passage of plasma from the
blood stream into the damaged tissue
v. Pain – due mainly to tissue destruction and, to
a lesser extent, swelling.

9. THIRD LINE OF DEFENSE
• Sometimes the second line of defense is still not enough
and the pathogen is then heading for the body's last line
of defense, the immune system.
• The immune system recognizes, attacks, destroys, and
remembers each pathogen that enters the body. It does
this by making specialized cells and antibodies that
render the pathogens harmless.
• Unlike the first line and second line defense the immune
system differentiates among pathogens.
• For each type of pathogen, the immune system produces
cells that are specific for that particular pathogen.

10. • The Immune System includes all
parts of the body that help in the
recognition and destruction of
foreign materials.
• Parts of the immune system:
 white blood cells(phagocytes
and lymphocytes)
 bone marrow
 lymph nodes
 tonsils
 thymus
 spleen

11. TYPES OF IMMUNITY
P A S S IV E A C T IV E
• Source: It is developed • Source: It is developed by
when ready-made an individual’s own cells in
antibodies are inoculated response to an infection or
from outside. a vaccine.
• Side effects: It may cause • Side effects: It has no side
reaction. effects.
• Period of relief: It provides • Period of relief: It provides
immediate relief. relief only after long
• Period of effectiveness: It period.
is short lived • Period of effectiveness: It
is long lasting.

12. • The natural passive immunity occurs,
when the maternal IgG type
antibodies is passed to the foetus
through the placenta. It is very much
helpful in the initial 6 months of the
infant’s life when the immune system
is still developing.
• In the artificial passive immunity, we
are introducing immunoglobulin or
pre formed animal based antibodies
(antiserum) to a non immune person.
This can be used, following exposure,
to a pathogen.

13. • It is named as naturally
acquired active immunity
because, the person develops
the full fledged infection to the
organism and later finds himself
resistant to that organism.
• In the artificial acquired active
immunity, the patient is
introduced with an organism
(usually attenuated) along with
substances to activate the
immune response.

14. DISEASES OF THE IMMUNE
SYSTEM
• HAY FEVER: is your immune system's response
FEVER
to foreign material in the air you breathe.
• Hay fever usually refers to allergies to outdoor,
airborne materials such as pollens and molds.
• A particular kind of antibody, IgE is released
causing very sensitive reaction to the allergens.
• Histamine is produced resulting sneezing,
difficulty breathing, runny nose.
• Antihistamines and inhalers relieve symptoms.

15. • ASTHMA: is a disorder that causes the airways
ASTHMA
of the lungs to swell and narrow, leading to
wheezing, shortness of breath, chest
tightness, and coughing.