Download Immune Cells - Morgan Community College

Chapter 13
The Immune Response
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Innate Immunity
• Always present
• Attacks nonself microbes
• Does not distinguish between different microbes
• Mechanisms include:
– Epithelial barriers
– Phagocytic cells
– Plasma proteins
– Cell messenger molecules
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Adaptive Immunity
• Attacks specific microbes (antigens)
• Develops after exposure to the specific antigen
• Mechanisms include:
– Humoral immunity (antibody proteins in the
blood that attack the specific antigen)
– Cell-mediated immunity (phagocytic cells
that attack the specific antigen)
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
Tell whether the following statement is true or false.
A vaccination is an example of adaptive immunity.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
True
Rationale: 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.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Antigen-Presenting Cells Tell the Immune
System What to Attack
• Eat the invading antigen
• Break it down into
pieces called epitopes
• Put epitopes on the cell
surface, attached to
MHC II proteins
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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 being
displayed will respond
to it
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
a. T lymphocytes
Rationale: As you can see in slide 8, the virus is attaching
itself to CD4 receptor sites, located on T cells (T
lymphocytes). Only helper T cells have this receptor.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
MHC I and MHC II Proteins Both Display
Antigens (cont.)
• MHC II proteins tell
helper T cells to
start an immune
response against
the antigen
• MHC I proteins tell
cytotoxic T cells to
kill the infected cell
before it can infect
other cells
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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 antigenpresenting cell to
activate them
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
T Lymphocytes Differentiate
in the Thymus
• Helper T
cells (CD4+)
• Cytotoxic T
cells (CD8+)
– CD4
receptors
attach to
MHC II
proteins
– CD8
receptors
attach to
MHC I
proteins
– Start an
immune
response
– Kill infected
cells
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
All but which of the following are 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.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
c. They signal the start of the immune response.
Rationale: CD8 receptors do all of those things but 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.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Two Kinds of Helper T Cells
• TH1 cells
– Stimulate the cytotoxic T cells and other
phagocytic cells to attack the antigen
• TH2 cells
– Stimulate the B cells to create antibodies
against the antigen
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
TH Cells Release Cytokines
• Cytokines are chemicals that control the immune
response
– Inflammatory mediators: cause fever; attract
WBCs to the infection
– Growth factors: cause WBCs to divide and
mature
– Cell communication molecules: used to
control activity of other WBCs
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
Which immune cell creates antibodies in response to
antigens?
a. Cytotoxic T lymphocytes
b. Helper T lymphocytes
c. Cytokines
d. B lymphocytes
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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 mucous 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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Discussion
A woman has type A blood.
• What antigens does she have on the surface of her
red blood cells?
• What antibodies against 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?
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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?
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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?
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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?
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
Tell whether the following statement is true or false.
Active immunity is achieved much more quickly than
passive immunity.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
False
Rationale: 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.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins