Genetics of Immunity
Part 1
BIO 2343
Oklahoma City Community College
Dennis Anderson
1
Function of the Immune System
• Protect the body from
foreign cells
– Pathogens = disease
causing organisms
• Destroy abnormal
body cells
– Cancer cells
2
Antigen
• A molecule that
stimulates the immune
system to respond
• Many are present on
the surface of cells
3
Self and Not Self
• Self = bodies own cell
surface molecules
– Not antigenic to ones’
self but may be to
another person
• Not Self = antigens
from a foreign cell or
mutated body cell
4
Blood Types
• Blood types are determined by the antigens
on red blood cells
• Type A has the A antigen
• Type B has the B antigen
• Type AB has both the A and the B antigen
• Type 0 has neither the A or B antigen
5
A Antigen for Type A Blood
6
B Antigen for Type B Blood
7
A and B Antigen for Type AB
Blood
8
Neither A nor B Antigens for
Type O Blood
9
Name the antigens for each blood type
A A
B B
AB A,B
O ----
10
Antibodies
• Molecules made by the immune system
• Attach to specific antigens
• Antibodies are made for antigens the body
does not have
• Person with type A blood has the B
antibody
– The A antibody would attack their own cells
11
Antibody B
• Has shape to connect
with antigen B=
• Produced by people
with type A and type
O blood
12
Problem
• A person with type A blood receives a
transfusion with type B blood.
• How will the persons’ immune system
respond?
13
14
Antibody B
• Reacts with B antigen
• Agglutinates (clumps
together) thousands of
foreign cells so they
can be destroyed
15
Antibody A
• Has shape to connect
with antigen A=
• Produced by people
with type B and type
O blood
16
Problem
• Max has type B blood and receives a
transfusion with type A blood.
– Max will have antibody A since he has type B
blood
• How will his immune system respond?
17
Antibody A reacts with the A
antigen
18
Antibody A
• Reacts with A antigen
• Agglutinates (clumps
together) thousands of
foreign cells so they
can be destroyed
19
D Antigen
• D antigen for positive
blood
• No D antigen for
negative blood
• D antigen is also
called the Rh factor
– Named after rhesus
monkey that has same
blood types as man
20
Rh Incompatibility
• Mother Rh-
• Fetus Rh+
• Mother produces
antibody D
– Crosses placenta
– Attacks blood of fetus
21
Problem
• Rh- is a recessive trait.
• A woman is Rh+. Her father is Rh-
– What does that make her?
• She marries an Rh- man
• What is the chance of them producing a
child that is Rh-?
22
RR = Rh+
Rr = Rh+
rr = Rh-
r r
R Rr Rr
50% chance for Rh-
r rr rr
23
Rhogam
• Injected into Rh- woman pregnant with an
Rh+ child
– During pregnancy and immediately after birth
• Destroys fetal Rh+ cells in mothers body
– Therefore she will not make antibodies that will
affect the next pregnancy
24
More RBC Antigens
• Over 50 antigens in addition to A, B & D have
been discovered
• M
• N
• S
• Se
• Levy
• Lewis
• + many more
25
Major Histocompatibility
Complex (MHC)
• Cell surface proteins (in addition to
Antigens on RBCs) that identify “self” to
the immune system
• Controlled by 70 genes
• Includes HLA antigens
26
HLA Antigens
• Human Leukocyte Antigens
• Originally discovered on leukocytes (white
blood cells)
• Found on most body cells
• Thousands of possible combinations of
HLA antigens
• Transplants more successful if donor and
recipient have similar HLA antigens
27
Major Components of Immune
Response
• 1st line of defense
– Physical barriers
• 2nd line of defense
– Innate defense
• 3rd line of defense
– Specific acquired immunity
28
Physical Barriers: 1st Line of
Defense
Nonspecific ( protect against
most foreign cells)
• Skin
• Acid
– Stomach
– Vagina
• Mucus
• Saliva
• Tears
29
Innate Defenses: 2nd Line of
Defense
Nonspecific defenses already present in the body
• Phagocytosis
• Complement system
• Fever
• Inflammation
30
Phagocytosis
Engulfing a cell (pathogen)
Pathogen
White Blood Cell
31
Complement System
• Series of proteins that help (complement)
several defensive mechanisms
• Dismantle virus proteins
• Stimulate the release of histamine
• Attract phagocytes
• Puncture cell membrane of bacteria
32
Fever
• Slows the growth of bacteria
– Sequesters iron in the liver
• Less available for bacteria to use
• Speeds up immune response
33
Inflammation
• Bodies response to tissue injury
• Classic signs
– Heat
– Redness
– Swelling
– Pain
• Steps of inflammation illustrated on the
next few slides
34
Skin
Blood
35
Tissue Damaged
Bacteria
36
Histamine released from mast cells
37
Histamine makes capillary more permeable
Plasma Leaks Out
38
Capillary More Permeable
Antibodies Leaks Out
39
Capillary More Permeable
WBCs leave capillary
40
Wall of Fibrin Forms
41
Pus forms from dead bacteria and WBCs
42
Pus drains, inflammation subsides
43
THE END
Part 1
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