Essentials of Pathophysiology
CHAPTER 15
INNATE AND ADAPTIVE IMMUNITY
PRE LECTURE QUIZ (TRUE/FALSE)
T

F

T

F

T

Active immunity is acquired through immunization
or actually having the disease.
T lymphocytes are responsible for humoral
immunity.
Adaptive immunity (also called acquired
immunity) refers to immunity that is acquired
through previous exposure to infectious and other
foreign agents.
The thymus does not play a role in the immune
response.
Passive immunity represents a temporary type of
immunity that is transferred from another source,
such as in utero transfer of antibodies from
mother to infant.
PRE LECTURE QUIZ

Antigens
IgE
________________ immunity (also called natural or
native immunity) consists of cellular and
biochemical defenses that are in place before
infection and respond rapidly to it.
There are five classes of __________________: IgG,
IgA, IgM, IgD, and IgE, each with a different role in
Immunoglobulin the immune defense strategy.


The __________________, a large secondary
lymphoid organ located high in the left abdominal
cavity, functions to filter antigens from the blood and
is important in the response to systemic infections.

Substances that are foreign to the host and can
stimulate an immune response are known as
__________________.

____________________ is the class of
immunoglobulin that is involved in allergic and
hypersensitivity reactions.
Innate
spleen
IMMUNE MECHANISMS
IMMUNE SYSTEM
INNATE IMMUNITY




Always present
Attacks nonself microbes
Does not distinguish between different microbes
Mechanisms include:
 Epithelial barriers
 Phagocytic cells
 Plasma proteins
 Cell messenger molecules
ADAPTIVE IMMUNITY
Foreign substance that
causes us to Generate
Antibodies
AntiGen

Attacks specific microbes (antigens)

Develops after exposure to the specific antigen

Mechanisms include:
Proteins we make that
attack specific invaders
 Humoral
immunity (antibody proteins in the
blood that attack the specific antigen)
 Cell-mediated
immunity (phagocytic & TC cells
that attack the specific antigen)
QUESTION
True or False:
A vaccination is an example of adaptive
immunity.
ANSWER
True
In adaptive/acquired immunity, specific antigens
are attacked, and immunity develops after
exposure to the specific antigen. When you get
a vaccine, you are getting a live, weakened, or
dead microbe (a specific antigen). Your body
develops antibodies to attack that antigen after
you are exposed.
IMMUNE CELLS


Regulatory cells control the immune response
 Helper T cells
 Suppressor T cells
 Antigen-presenting cells
Effector cells then carry out the attack on the
antigen
 Cytotoxic T (or killer T) cells
 B cells (produce antibodies)
 Leukocytes
ANTIGEN-PRESENTING CELLS TELL THE
IMMUNE SYSTEM WHAT TO ATTACK
APC
• Eat the invading
antigen
• Break it down into
pieces called
epitopes
• Put epitopes on
the cell surface,
attached to MHC II
proteins
NATURAL KILLER CELL (NK)
ANTIGENS ATTACHED TO MHC PROTEINS
CAN BE “SEEN” BY
IMMUNE CELLS
The immune cells
have receptors that
attach to MHC
proteins and “see” the
antigen
 They also have
antigen receptors
 Only those T cells
whose antigen
receptors “fit” the
antigen displayed will
respond to it

APC
MHC I AND MHC II PROTEINS BOTH DISPLAY
ANTIGENS

MHC II proteins display
antigens eaten by a
phagocytic cell

MHC I proteins display
antigens made inside
an infected cell
Only On
APC
cells
On All
cells
CD 4 is required
for docking with
MHC II
CD 8 is required
for docking with
MHC I
MHC I AND MHC II PROTEINS BOTH DISPLAY
ANTIGENS (CONT.)

MHC II proteins on APC
cells tell helper T cells
to start an immune
response against the
antigen Stimulate B and
TC cells

MHC I proteins on any
body cell tell cytotoxic T
cells to kill the infected
cell before it can infect
other cells
QUESTION
AIDS is an example of a disease in which patients
are immunocompromised. Which immune
cells are affected in AIDS?
a. T lymphocytes
b. B lymphocytes
c. Antigen presenting cells
d. Leukocytes
ANSWER
T lymphocytes
As you can see in slide 08, the virus is attaching
itself to CD4 receptor sites, located on T cells
(T lymphocytes). Only helper T cells have this
receptor.
a.
MHC I AND MHC II PROTEINS


MHC II proteins display antigens eaten by a phagocytic
cell
MHC I proteins display antigens made inside an
infected cell
MHC I AND MHC II PROTEINS


MHC II proteins tell T helper cells to start an immune
response against the antigen
MHC I proteins tell T cytotoxic cells to kill the infected
cell before it can infect other cells
WHERE DO LYMPHOCYTES COME FROM?

Stem cells in the bone
marrow or fetal liver

B cells mature in the bone
marrow

T cells mature in the
thymus

Then they move to the
lymph nodes to wait for an
antigen-presenting cell to
activate them
Bone Marrow
T LYMPHOCYTES DIFFERENTIATE
IN THE THYMUS

Helper T cells (CD4+)
 CD4 receptors
attach to MHC II
proteins
 Start an immune
response
• Cytotoxic T cells
(CD8+)
– CD8 receptors
attach to MHC I
proteins
– Kill infected
cells
QUESTION
All but which of the following is true about CD8
receptors?
a. They can be found on cytotoxic T cells.
b. They attach to MHC I proteins.
c. They signal the start of the immune response.
d. They differentiate in the thymus.
ANSWER
c.
They signal the start of the immune response.
CD8 receptors do all of those things, but they don’t kick
off the immune response (the helper T cell does that).
CD8 receptors are found on cytotoxic T cells; as the
name implies, they kill the infected cell.
TWO KINDS OF T HELPER CELLS

TH1 cells
 Stimulate
the T cytotoxic cells and other
phagocytic cells to attack the antigen

TH2 cells
 Stimulate
the B cells to create antibodies
against the antigen
TH CELLS RELEASE CYTOKINES
Cytokines are the “Voice” of the TH cells

HELLO
Cytokines are chemicals that control the immune
response of the cells with receptors (“ears”)
 Inflammatory mediators: cause fever;
 Chemotaxic cytokines attract WBCs to the
infection
 Growth factors: cause WBCs to divide and
mature
 Cytokines are cell communication molecules:
used to control activity of other WBCs
B LYMPHOCYTES
Like T cells,
B cells have
antigen
receptors
 They can only
be activated to
attack the
antigen if a
helper T cell
shows it to
them

ACTIVATED B CELLS DIVIDE INTO
TWO KINDS OF CELLS:

Memory B cells remain
in the body


In the future, they will
fight off the antigen
without a helper T cell
telling them to do so
Plasma cells create
antibodies, - special
proteins designed to
attach to that antigen
and destroy it
QUESTION
Which immune cell creates antibodies in
response to antigens?
a. Cytotoxic T lymphocytes
b. Helper T lymphocytes
c. Cytokines
d. B lymphocytes
ANSWER
d.
B lymphocytes
Rationale: Remember that antibodies are
created in response to antigens. B
lymphocytes have antigen receptors and are
activated to attack a specific antigen if a
helper T cell directs them to do so.
ACTIVATED B CELLS DIVIDE INTO
TWO KINDS OF CELLS:

Memory B cells remain in the body
 In
the future, they will fight off the antigen
without a T helper cell telling them to do so

Plasma cells create antibodies, special
proteins designed to attach to that antigen
and destroy it
QUESTION
Which immune cell creates antibodies in
response to antigens?
a. Cytotoxic T lymphocytes
b. Helper T lymphocytes
c. Cytokines
d. B lymphocytes
ANSWER
B Lymphocytes
Remember that antibodies are created in
response to antigens. B lymphocytes have
antigen receptors and are activated to attack a
specific antigen if a T helper cell directs them
to do so.
d.
DISCUSSION:
Which would cause the most severe immune
deficiency?

A lack of B cells

A lack of Tc cells

A lack of TH1 cells

A lack of TH2 cells

A lack of macrophages
ANTIBODIES OR IMMUNOGLOBULINS

IgG: circulates in body fluids, attacking antigens

IgM: circulates in body fluids; has five units to
pull antigens together into clumps

IgA: found in secretions on mucus membranes;
prevents antigens from entering the body

IgD: found on the surface of B cells; acts as an
antigen receptor

IgE: found on mast cells in tissues; starts an
inflammation
ANTIBODY/IMMUNOGLOBIN STRUCTURE
COMPLEMENT PROTEINS

Highly toxic proteins

Circulate in the blood
in an inactive form

When an antibody
attaches to an antigen,
the resulting immune
complex can activate
complement

Complement then
destroys the antigen
DISCUSSION
A woman has type A blood.

What antigens does she have on the surface of
her red blood cells?

What RBC antibodies against other RBC antigens
has her body produced?

What will happen if she is given type B blood?

What will happen if her blood is given to a person
with type B blood?

What will happen if she is given type O blood?
PRIMARY IMMUNE RESPONSE
The macrophage must
eat the antigen, then
present it to TH cells
 TH cells must activate B
cells
 B cells produce
antibodies
 Then plasma antibody
levels rise
 This can take 2–3 weeks
 Vaccination produces a
primary immune
response

SECONDARY IMMUNE RESPONSE
Memory B cells
respond to the
antigen
immediately
 Plasma antibody
levels rise within
days
 Booster shots
cause a secondary
immune response
so antibody levels
will be high before
the disease is
encountered

ACTIVE IMMUNITY VS. PASSIVE IMMUNITY
Scenario

A woman was bitten by a rattlesnake last
summer; she received antiserum against the
snake venom, and she survived

This summer she will be vacationing in the
same area
Question:

Should she get a booster shot against
snakebite before her vacation? (next slide)
ANTISERUM



Protective immunoglobulin—primarily of the IgG class—can
be prepared from the blood of humans or other species
(e.g., horses or rabbits) that have already developed
specific immunity against the relevant antigens. These
preparations are known as antiserums.
Human IgG is slowly broken down in the recipient’s body,
the concentration falling by about one-half every three
weeks, so that effective amounts of antibody can be
present for two or three months.
Because antivenom is derived from animal antibodies,
people generally display an allergic response during
infusion, known as serum sickness.
ACTIVE IMMUNITY VS. PASSIVE IMMUNITY (CONT.)
Scenario

A woman’s baby is HIV-positive
Questions:

Does this mean the baby has HIV?

Does it mean the father has HIV?

Does it mean the mother has HIV?
ACTIVE IMMUNITY VS. PASSIVE IMMUNITY
(CONT.)
Scenario:

A woman's baby is HIV-positive
Question:

Does this mean the baby has HIV?

Does it mean the father has HIV?

Does it mean the mother has HIV?
ACTIVE IMMUNITY VS. PASSIVE IMMUNITY
(CONT.)
Discussion:
 The woman says that since her immunity
went to her baby, the baby will not need
any vaccinations. Is this correct?
QUESTION
True or False:
Active immunity is achieved much quicker than
passive immunity.
ANSWER
False
In active immunity, an individual is exposed to an
antigen, the immune response begins, and
antibodies are formed in 7–10 days. In passive
immunity, antibodies are created outside the
host and injected, giving the individual
immunity immediately.