Transcript Lecture 7: The body’s defenses

The body’s defenses
Reading: Ch. 43; Keywords
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Lines of defense
Lymphatic system
Inflammation
Features of immune
system
Memory B-cells
Primary and secondary
immune responses
Antibody
Antigen
Agglutination
macrophage
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lymphocyte
Phagocytosis
Complement system
Humoral immunity
Cell-mediated
immunity
• B cell
• Helper T cell
• Cytotoxic T cell
Overview
Non-specific
• First line
– Skin
– Mucous membranes
– Secretions of skin and mucous membranes
• Second line
– Phagocytic white blood cells
– Anti-microbial proteins
– Inflammatory response
Second line of defense - macrophage
Inflamation
Focus on immune system
(3rd line of defense)
• Protects body against specific invaders
Key features
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Specificity
Diversity
Memory
Self/Nonself Recognition
First the
major players:
Lymphocytes
The
lymphatic
system
Two types of immune responses
• Humoral
• Cell-mediated
Key features
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Specificity
Diversity
Memory
Self/Nonself Recognition
Humoral immunity
Humoral
immunity:
B cells and
clonal
selection
There are a variety of B cells
One B cell becomes activated and
proliferates
Some B cells become plasma
cells that secrete antibodies
Some B cells
become plasma
cells that secrete
antibodies
Some B cells become memory
cells
Some B
cells
become
memory
cells
Memory cells function in
secondary immune response
• Primary immune response - first exposure
• Secondary immune response - second
exposure
Primary and secondary immune
responses
Summary
• Lag in primary response due to proliferation
from a single clone
• Secondary (2°) response is from multiple
memory cells
• 2° response has less of a lag and is stronger
What do antibodies do?
Inactivate antigens
Neutralization
Agglutination
of antigen
bearing
particles
Precipitation of soluble antigens
Inactivate antigens
• Neutralization
• Agglutination
• Precipitation
These mechanisms enhance
phagocytosis
Antibodies inactivate antigens
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Neutralization of invaders
Agglutination
Precipitation of soluble antigens
The above enhance phagocytosis
• One final mechanism: Complement system
Complement system: Step
1 attachment to pathogen
Step 2:
Recruitment of
complement
proteins
Step 3: Activation
Step 4: pore
formation
Summary
• Complement proteins interact with
antibodies to kill invading cells
• Binding of antibody is followed by
attachment of complement proteins
• Protein complex becomes activated
• Pore is formed in pathogen’s membrane
• Goodbye pathogen
Two types of immune responses
• Humoral
• Cell-mediated
Cell-mediated
• Complicated, involves cellular components
• Will briefly touch on role of helper T cells
Recall that T
cells are the
other type of
lymphocyte
Cell-mediated response happens
at the same time
Macrophage
engulfs invader
Antigens from
invader are
presented on
macrophage
cell surface
Helper T cells are
recruited
Helper T cells proliferate and
activate cytotoxic T cells and B cells
T cells infected with HIV