3rd Line – Immune
Response
B11-5-02 – Body’s response to viruses/bacteria
Immune System Video
The 3 Lines of Defense
The 1st line of
Defense
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Barriers
The 2nd line of
Defense
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Inflammatory response
The 3rd line of
Defense
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Immune response
Immune system distinguishes “self” from
“non-self”

Do not react with our own cells
Generates specific response to specific
invaders
Builds up resistance against Pathogens
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Antigen
Tailored to an individual threat
Most effective

Memory component
Improves response time
Immune Response
Two types of specific immune response
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Antibody-mediated
Cell-mediated
Antibody-Mediated
Immunity
Antibody-Mediated Immunity
Production of antibodies specific to a given
antigen
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Antibodies bind to the antigens on invaders
and kill or inactivate them
Antigens are molecules that cause antibody
production
Response provided by B cells
(lymphocytes derived from bone marrow)
Lymphocyste Video
In Response to Infection
A few days after an infection
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Antigens cause the production of large
amount of the antibody capable of interacting
with it
Specific antibodies bind specific antigens
Antibodies
Antibodies bind antigens in a lock-and-key
fashion

Forming antigen-antibody complex
Type of protein

Immunoglobulin
Y shaped molecules with
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Two heavy chains
Two light chains
Antibodies Cont.
Identify Antigens as either

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Self
Nonself
Bind non-self antigens clumping them
together making them inactive
Antibodies Cont.
Body only has antibodies for pathogens
that a host has encountered
When a new pathogen invades the body,
B-cells “learn” about new antigens and
develop appropriate antibodies
The B-Cells then circulate though the
body, releasing antibodies that bind to new
antigen
Antibodies Video 1
Antibodies Video 2
Antigens
Protein or polysaccharide that is present
on the plasma membrane
Cell-Mediated Immunity
Cell-mediated Immunity
Require direct physical contact with
antigens
Does not involve the production of
antibodies
Response provided by T-Cells
(lymphocytes derived from the thymus)
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Four types
1. Cytotoxic (Killer) T-Cells
Defend the body by destroying
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Foreign cells
Infected cells
Cancerous cells
Recognizes viral antigens on plasma
membrane of host cell
Attaches to plasma membrane of host cell
Secrete enzymes that digest host plasma
membrane

Punching holes
Infected cell’s cytoplasm leaks out and the
cell dies
The dead cell and its contents are
removed by phagocytes
2. Helper T-Cells
Regulate immune response by …
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Secreting messenger proteins
Direct contact with other cells
Helps Killer T-Cells and B-Cells to perform
their function
Are destroyed by the HIV virus in patients
with Acquired Immune Deficiency
Syndrome (AIDS)
3. Suppressor T Cells
Reduce the immune response of B cells
and T cells to keep them in check
4. Memory T Cells
Remain in the body awaiting the
reintroduction of the antigen
Grab a Text
Read and Make Notes
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13.3 INDUCED IMMUNITY
Active Immunity (250)
Passive Immunity (251)