Download The Body`s Lines of Defense

The Body’s Lines of
Defense
Pathogens
 Pathogens are disease causing organisms.
 The body has 3 lines of defense.
 The first 2 lines of defense are non specific and the 3rd
line is specific
First Line of Defense- Skin
 Skin is the largest organ in our body and provides a
barrier that normally cannot be penetrated by bacteria
and viruses.
 The skin uses acidic secretions that contain Lysozymes
(found in tears, saliva, mucous secretions, and
perspiration), which keep it at a pH range of 3 to 5.
 This is acidic enough to inhibit the growth of microbes.
First Line of Defense- Mucous
 Mucous can be found in the respiratory passage.
 Cells in the trachea produce a mucus that traps
microbes before they reach the lungs.
 Corrosive acids in the stomach destroy most of the
invading microbes carried into the body with food.
Second / Third Line of DefenseLeukocytes
 A second line / third line of defence acts if the invader
enters the body.
 Leukocytes are white blood cells that may engulf
invading microbes or produce antibodies.
 Leukocytes that take part in phagocytosis are part of
the bodies second line of defense and are non-specific.
 Leukocytes that produce antibodies are specific and
part of the body’s third line.
Phagocytosis
Phagocytosis is when white blood cells “eat” a pathogen and
release a chemical to destroy it.
Clip
Granulocytes
 One class of leukocytes, called granulocytes, contain
cytoplasmic granules and are produced in the bone
marrow.
 Eosinophils (parasites), basophils (allergies), and
neutrophils (pus) are 3 types of granulocytes.
 Some of these granulocytes are part of the third line of
defense and others are part of the second line of
defense.
Neutrophil Phagocytosis
Agranulocytes
 Agranulocytes do not have a granular cytoplasm, are
produced in the bone marrow but are modified in the
lymph nodes.
 Monocytes and lymphocytes are the 2 types of
agranulocytes.
 Monocytes turn into macrophages when they are
released by the blood stream and perform phagocytosis.
 Lymphocytes come in 2 forms: B Cells & T Cells. B Cells
produce antibodies, and T Cells seek the intruder and
organize the attack. Lymphocytes are part of the third
line of defense.
http://www.youtube.com/watch?v=UKwwvIaR9aI
Development of Leukocytes
Inflammatory Response
 Is triggered when tissue cells are injured by bacteria
 Characterized by swelling, heat, redness, and pain.
 Is a sign that a secondary defense is at work.
 (a) Patient X. Indicators are reduced red and white
blood cell counts.
 (b) Patient Z. Indicators are higher body temperature
and an elevated white blood cell count. The red blood
cell count is normal.
 (c) Patient Y. Indicators are increased white blood cell
count and reduced red blood cell count because white
blood cell growth in the bone marrow reduces the red
blood cell count numbers.
Case Study
 Hand out case study
Third Line of Defense- Lymphocytes
 Remember lymphocytes can be B Cells or T Cells
 Cell membranes of bacteria and outer coat of a virus
contain antigens.
 Antigens are any substance that triggers the formation
of antibodies.
Third Line of Defense- Lymphocytes
 Each cell in the human body has receptor sites that
allow nutrients to enter.
 Bacteria and viruses gain
entry to the cell through
these receptor sites.
Third Line of Defense- Lymphocytes
 Each antibody is specific to the antigen that has invaded
the body. For example: the antibody to fight strep
throat will not fight a cold virus.
Note that antibodies
are Y shaped
How the Body
Recognizes
Antigens
Remember our T Cell
lymphocytes and
B Cell lymphocytes
Helper T Cells are
1 type of T Cells
Killer T Cells
 Sometimes Killer T Cells (another type of T Cell) are
needed to stop viruses.
 Viruses can be evasive and can hide within the host cell.
If this occurs, Killer T Cells are sent on a, “Search and
Destroy,” mission.
 The Killer T Cell will puncture the cell membrane of the
host cell. This kills the body cell and the virus. It also
prevents the virus from reproducing.
Suppressor T Cells and Memory T Cells
 Once the battle between the invaders and the body is
won, Suppressor T Cells (Yet another type of T Cell)
signal the immune system to shut down.
 Memory T Cells (Yes, a type of T Cell), store info about
the antigen. If this antigen enters the body again, it will
be defeated before they become established in the
body.
Summary
 Start with HIV intro questions
HIV
 Human Immunodeficiency Virus
 HIV is the virus that causes AIDS (Acquired Immune
Deficiency Syndrome) .
 HIV has an 8- 10 year incubation period before
symptoms arise.
 The immune system becomes weakened. A decrease in
the function of CNS followed by bodyweight loss occurs.
 Eventually death by a secondary infection such as
pneumonia, meningitis, or fungal infection occurs.
Transmission of HIV
 Through sexual intercourse, blood transfusion, injection
with contaminated needle.
 HIV infected mother through placenta and breast milk.
What Actually Happens?
 HIV has a shape that provides access to the T Cell.
 Unlike other viruses, the T Cell will engulf it.
If T Cells are attacked, explain in a journal entry how this weakens the immune
system.
HIV Attacking Cells
 http://www.youtube.com/watch?v=U2h0ECyMWhE
 http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter24/a
nimation__hiv_replication.html
ELISA
 ELISA test (Enzyme-Linked Immunosorbent Assay
 Used to help detect diseases such as HIV
 http://www.youtube.com/watch?v=RRbuz3VQ100
 http://media.hhmi.org/biointeractive/vlabs/immunolog
y/index.html