Download Immune System – Part 2

Chapter 24
The Immune System
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey
© 2012 Pearson Education, Inc.
Lecture by Edward J. Zalisko
ADAPTIVE IMMUNITY
Responsible for specific response and immune
system memory
© 2012 Pearson Education, Inc.
24.5 Lymphocytes mount a dual defense
 B cells
– participate in the humoral immune response and
– secrete antibodies into the blood and lymph
– Attack pathogens OUTSIDE body cells!!!!
 T cells
– participate in the cell-mediated immune response,
– attack cells infected with bacteria or viruses, and
– Help bridge B-cell and Innate immune responses.
© 2012 Pearson Education, Inc.
Key Point to
Remember:
Each B and T cell
displays unique
set of antigen
receptors on cell
surface
Each receptor can
specifically bind to
a unique antigen
Stem cell
Bone
marrow
Via
blood
Immature lymphocytes
Thymus
Antigen
receptors
B cell
Via
blood
T cell
Final maturation
of B and T cells in a
lymphatic organ
Lymph
nodes,
spleen, and
other
lymphatic
organs
Humoral
immune response
Cell-mediated
immune response
Development of Immune System Memory by
CLONAL SELECTION
Legal Disclaimer:
Clonal selection occurs in a similar manner for
T cell-mediated immune memory
(the following events are fictional - any resemblance to
Historical characters is just coincidence - no B cells or
Pathogens were actually harmed in the making of this animation.
Animation: Role of B Cells
© 2012 Pearson Education, Inc.
CLONAL SELECTION
Primary immune response
1
B cells with
different
antigen
receptors
Antigen
receptor
on the cell
surface
Every B cell displays unique
antigen receptor on surface
CLONAL SELECTION
Primary immune response
1
B cells with
different
antigen
receptors
Antigen
receptor
on the cell
surface
2
Antigen
molecules
Antigen only binds to B cell with
complementary receptor
CLONAL SELECTION
Primary immune response
1
B cells with
different
antigen
receptors
Antigen
receptor
on the cell
surface
2
Antigen
molecules
3
First exposure
to the antigen
I WON THE
ANTIGEN
LOTTERY!!
The selected B cell now divides
rapidly!!!
Figure 24.7A_s4
Primary immune response
1
B cells with
different
antigen
receptors
Antigen
receptor
on the cell
surface
2
Antigen
molecules
3
First exposure
to the antigen
We’ll
hang out
And wait for the
next invasion
We’ll mark the
Pathogen for
Elimination!!
Antibody
molecules
4
Plasma cells - secrete antibodies
5
Memory cells
Figure 24.7A_s5
Secondary immune response
Alright boys, the pathogen is
Back!! Looks like we’re in
Charge of the second offensive Get ready to divide!!
Antigen
molecules
Second
exposure
to the same
antigen
Memory cells
Secondary immune response
Looks like we are off to fight
This pathogen again!
But now we can respond
Faster with a larger army - those
Bugs won’t know what hit them!
Memory cells
divide
Memory cells
Antibody
molecules
Plasma cells
Memory cells
Antibody concentration
2nd response
Second exposure
occurs
to antigen X,
quicker with
first exposure
greater
to antigen Y
magnitude!!
Secondary immune
response to
antigen X
First exposure
to antigen X
Primary immune
response to
antigen X
Antibodies
to Y
Antibodies
to X
0
7
14
21
Primary immune
response to
antigen Y
35
28
Time (days)
42
49
56
But what IS an Antibody?????
 Protein made of 4 separate subunits
 Sits on surface of B cells until B cell stimulated to
release antibodies into body fluids
© 2012 Pearson Education, Inc.
Figure 24.8A
Light chain
Heavy chain
Figure 24.8B
Antigen
Antigen-binding
sites
Antigen-binding site
VARIES between
each unique antibody
The CONSTANT
region defines Ab
class and effector
action
Light
chain
C
C
Heavy
chain
V = variable
C = constant
Antibodies mark antigens for elimination
Binding of antibodies to antigens
inactivates antigens by
Neutralization
(blocks viral binding sites;
coats bacteria)
Agglutination
of microbes
Precipitation of
dissolved antigens
Activation of the
complement system
Complement
molecule
Bacteria
Virus
Antigen
molecules
Bacterium
Foreign cell
Enhances
Leads to
Phagocytosis
Cell lysis
Macrophage
Animation: Antibodies
Hole
T cell mediated immune function
 T-Cells Detect presence of foreign antigens on SURFACE
of virally or bacterially infected body cells
 2 types of T cells:
– Helper T cells -- stimulate B-cell and T-cell mediated
immune responses
– Cytotoxic T cells
– DESTROY infected cells as marked by Helper T cells
Animation: Helper T Cells
Video: T Cell Receptors
© 2012 Pearson Education, Inc.
Animation: Cytotoxic T Cells
Figure 24.UN01
The humoral immune response:
makes
which bind to
B cell
Antibodies
Antigens in
body fluid
The cell-mediated immune response:
T cell
Infected
body cell
Self-nonself complex
Infected body cells will
display antigens of pathogen
on cell surface
Phagocytic cell
(yellow) engulfing
a foreign cell
Self-nonself
complex
Macrophage
Microbe
B cell
T cell
receptor
Interleukin-2
stimulates
cell division
5
3
1
2
Helper
T cell
4
6
7
Interleukin-2
activates B cells
and other T cells
Self protein
Antigen from the microbe
(nonself molecule)
Antigen-presenting
cell
Binding
site for the
self protein
Binding
site for the
antigen
Humoral
immune
response
(secretion of
antibodies by
plasma cells)
Cytotoxic
T cell
Cell-mediated
immune
response
(attack on
infected cells)
Helper T cells are trained to recognize foreign
antigens and alert B cells and Cytotoxic T cells
How are B and T cells trained to recognize ‘self’
vs. ‘non-self’ antigens????
 Each of us display a unique protein and
carbohydrate ‘fingerprint’ on the surface of our cells
– This fingerprint is referred to as the MHC protein complex
 During development, B and T cells are exposed to
MHC proteins
 Any B or T cells that have antigen receptors that can
bind to ‘self’ antigens are DESTROYED!!
 This is called CLONAL DELETION.
© 2012 Pearson Education, Inc.