Download THE IMMUNE SYSTEM CH 43

THE IMMUNE SYSTEM
CH 43
A group of cells, molecules, and
organs that act together to fight off
foreign invaders
• All animals have innate immunity
• Vertebrates have adaptive immunity
I. The innate immune response in
mammals Involves nonspecific
responses to pathogens
• Barrier defenses: prevent pathogen entry
• Skin is a physical barrier
• Tears mucus and saliva are inhospitable to
invaders
• Mucus is thick and traps invaders
• cellular defenses: If the invader passes thru
skin
– White blood cells phagocytose invader
– Damaged cells release signals like histamine
causing increased blood supply to the area and
clot formation and inflammation/swelling/heat
– Fevers to generate heat which can inhibit growth
of microbes and increases phagocytosis
http://www.uic.edu/classes/bios/bios100/lectures/two_lines_of_defense.htm
II. The adaptive (or specific) immune
response
• launches a SPECIFIC attack against the
invader
• Properties of the adaptive immune response
– Only works if the invader is present
– Is specific to that invader
– Has memory
– Can distinguish between self and nonself
• The adaptive immune response is the result of
the production of antibodies against a specific
antigen
• Antigen: a specific molecule, usually a protein
that is foreign to the organism (nonself) and
stimulates the immune system to make
antibodies
• http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapt
er22/animation__antigenic_determinants__epito
pes_.html
A. Components of adaptive immune response
1. macrophages or white blood cells
• circulate thru blood and
phagocytose foreign
invaders and present the
antigen on their surface
with MHC protein
• Macrophages are antigen
presenting cells
• 2. Lymphocytes
– involved in antibody production
– Originate from stem cells
– Two types:
• B-cells
• T- cells
• B-cell
• Make antibodies
• Each different Bcell makes only
one type of
antibody
• They sit dormant
until the antigen
stimulates them
to make
antibodies
• Has B cell
receptor on it
• T-cells
• Helper T-cells
helps the B-cells
make antibodies
• Killer T-cells kill
cells with foreign
invader
• Supressor T-cells
suppress T-helper
and B-cells
• Has T cell receptor
on it
3. Antibodies
• (Compare b t antibody)
• Bind to the
foreign invader
and inactivate
it
• Produced by B
cells Each
antibody will
only inactivate
one antigen
• Antibodies are secreted form of B cell
receptor
• T cell receptor is one side of B cell
receptor/antibody
• There is a single B cell, T cell, antibody for
each antigen
B. Gene rearrangement explains why
there are so many T and B cells:
http://highered.mheducati
on.com/sites/0072556781/
student_view0/chapter32/
animation_quiz_2.html
gene rearrangements of T cell and B cell receptor
genes begins to occur producing millions of different
B and T cells. This is maturation/differentiation
• Self Tolerance:
– During maturation and differentiation of B and T
cells, if any produce receptors to body cells what
would happen?
– What occurs naturally?
C. The Primary immune response: first
exposure to pathogen
1. APC phagocytoses pathogen, digests it, and
presents the antigen along with MHC class II
protein. A specific helper T cell binds to
presented antigen with its receptor and becomes
activated
2 and 3. Activated helper T binds to B cell with
antigen on the B cell receptor. Helper T
secretes cytokines that cause proliferation of B
cell producing plasma cells, which make
antibodies, and memory B cells
• Circulating antibodies bind free pathogens,
preventing their activity and inducing their
destruction
Activated helper T also activates a specific killer T
cell.
Infected cell present antigen on MHC class I
molecule. Killer T binds to antigen, secretes perforin,
and infected cell dies.
D. Secondary Immune response
• Subsequent exposure to same pathogen
• Activated B, helperT and killer T from primary
response proliferate forming memory cells
• Second exposure activates memory cells to
immediately destroy pathogen
• http://highered.mheducation.com/sites/007
2507470/student_view0/chapter22/animatio
n__the_immune_response.html
Summary of adaptive immune
response:
• The humoral immune response results in
production of antibodies
• The cell-mediated immune response results
in death of infected cells
• What cells are involved in humoral response?
• What cells are involved in cell-mediated
response?
III. Active vs Passive Immunity
A. active immunity
• Production of antibodies and memory cells
from exposure to pathogen
– Becoming sick
– Getting immunized
B. passive immunity
• Acquisition of antibodies without exposure
to pathogen
– Naturally from maternal to fetal blood or mom to
baby thru breast milk
– Artificially by injection of IgG
What is the main difference between active
and passive immunity?
IV. Self vs Nonself
• Where are MHC class I found?
• Where are MHC class II found?
• All cells have MHC class I proteins on cell
membrane
• There are about 600 different forms and each
cell has 6-8 of them
• There are many different combinations in the
human population
• Immune system recognizes its own MHC
combinations as self and all others as nonself
resulting in rejection