Ch15 - Morgan Community College

Essentials of Pathophysiology

CHAPTER 15 INNATE AND ADAPTIVE IMMUNITY

PRE LECTURE QUIZ (TRUE/FALSE) T

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F

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T

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F

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T

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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. 

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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.

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Substances that are foreign to the host and can stimulate an immune response are known as __________________.

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____________________ 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

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Attacks specific microbes (antigens)

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Develops after exposure to the specific antigen

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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 

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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

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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

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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 

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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 

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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

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B cells mature in the bone marrow

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T cells mature in the thymus

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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

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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 

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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

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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

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A lack of Tc cells

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A lack of TH1 cells

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A lack of TH2 cells

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A lack of macrophages

ANTIBODIES OR IMMUNOGLOBULINS 

IgG: circulates in body fluids, attacking antigens

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IgM: circulates in body fluids; has five units to pull antigens together into clumps

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IgA: found in secretions on mucus membranes; prevents antigens from entering the body

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IgD: found on the surface of B cells; acts as an antigen receptor

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IgE: found on mast cells in tissues; starts an inflammation

ANTIBODY/IMMUNOGLOBIN STRUCTURE

COMPLEMENT PROTEINS 

Highly toxic proteins

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Circulate in the blood in an inactive form

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When an antibody attaches to an antigen, the resulting immune complex can activate complement

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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?

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What RBC antibodies against other RBC antigens has her body produced?

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What will happen if she is given type B blood?

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What will happen if her blood is given to a person with type B blood?

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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

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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 

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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?

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Does it mean the father has HIV?

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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?

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Does it mean the father has HIV?

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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.