Susan Capasso, Ed.D., CGC St. Vincent’s College Suggested Lecture Presentation Copyright © 2009...

Susan Capasso, Ed.D., CGCSt. Vincent’s College

Suggested Lecture Presentation

Copyright © 2009 Pearson Education, Inc.

Chapter 13

Body Defense Mechanisms



The body’s defense system targets pathogens and cancerous cells

The body has three lines of defense The immune system distinguishes self

from nonself The immune system mounts antibody-

mediated responses and cell-mediated responses



The cell-mediated immune response and the antibody-mediated immune response have the same steps

Immunity can be active or passive Monoclonal antibodies are used in

research, clinical diagnosis, and disease treatment

The immune system can cause problems


The Body’s Defense System

The body’s defense mechanisms target pathogens and cancerous cells


The Body Has 3 Lines of Defense

The body has three lines of defense Nonspecific

1. Physical and chemical surface barriers

2. Internal cellular and chemical defense Specific

3. Immune response


The Body Has 3 Lines of Defense

Figure 13.1

First line of defense:Nonspecific physical andchemical surface barriers

Second line of defense:Nonspecific internal cellular

and chemical defense

Third line of defense:Immune response

Specific defensesNonspecific defenses

If pathogenpenetrates barriers

If pathogensurvives nonspecific

internal defenses


Nonspecific Surface Barriers

Physical and chemical barriers The skin

Nearly impenetrable Waterproof Resistant to most toxins and enzymes of

invading organisms Sweat and oil glands

Produce chemicals that slow or prevent the growth of bacteria



Physical and chemical barriers (continued) Mucus of the respiratory and digestive tracts

Sticky and traps many microbes The lining of the stomach

Produces hydrochloric acid and digesting enzymes that destroy pathogens



Physical and chemical barriers (continued) Urine

Slows bacterial growth with acidity Washes microbes from urethra

Saliva and tears Contain lysozyme, an enzyme that kills

bacteria



Figure 13.2 (1 of 2)


Nonspecific Internal Defenses

The second line of defense Defensive cells Defensive proteins Inflammation Fever



Table 13.1



Animation—The Inflammatory ResponsePLAY



Defensive cells include neutrophils and macrophages They engulf pathogens, damaged tissue, or

dead cells by the process of phagocytosis



Figure 13.3



Eosinophils Attack pathogens that are too large for

phagocytosis, such as parasitic worms Get close to the parasites and discharge

destructive enzymes that destroy them

Natural killer (NK) cells Search out abnormal cells, including

cancerous cells, and kill them



Figure 13.4



The body’s non-specific cellular defenses use two types of defensive proteins Interferons Complement system



Before a virally–infected cell dies, it secretes small proteins called interferons that Attract macrophages and natural killer cells Stimulate neighboring cells to make proteins

that prevent the viruses from replicating



The complement system A group of proteins that enhance both

nonspecific and specific defense mechanisms by Destroying pathogens Enhancing phagocytosis Stimulating the inflammatory response



Inflammatory response destroys invaders and helps repair and restore damaged tissue Redness Heat Swelling Pain



The increased blood flow to damaged tissue stimulates mast cells and basophils to release histamine Increases blood flow by dilating blood

vessels and increasing the permeability of the capillaries



Fluid leaks from the capillaries Causes swelling

Blood flow increases Causes redness and warmth



Fever An abnormally high body temperature

caused by pyrogens Chemicals that reset the brain’s

thermostat to a higher temperature

A moderately higher body temperature helps fight bacterial infections



Figure 13.7



Table 13.1


Specific Immune Responses

The third line of defense is the immune system Has specific responses and memory


Specific Immune Responses

Immune response The body’s specific defenses Work together in the recognition and

destruction of specific pathogens Have memory


The Immune System Distinguishes Self from Nonself

The body must be able to distinguish a foreign organism or molecule from self

MHC markers are found on our own cells and mark them as belonging to us


The Immune System Distinguishes Self from Nonself

Figure 13.8


The Immune System

Antigens Nonself substances that trigger an immune

response Usually large molecules, such as proteins,

polysaccharides, or nucleic acids


The Immune System

When an antigen is detected B lymphocytes and T lymphocytes that

recognize the antigen are stimulated to divide repeatedly


The Immune System

Some of these cells attack and eliminate the invader

Others are stored in a state of suspended animation as a form of memory of the invader Available to attack if there is a reoccurrence


Antibody-Mediated Responses

Antibody-mediated immune responses Defend against antigens that are free in

body fluids, including toxins or extracellular pathogens



B cells use antibodies to neutralize the antigen




Antigen

Macrophage

Helper T cell

Effectorhelper T cell

Memoryhelper T cell

Naive B cell Naivecytotoxic T cell

Antibody-mediated response

Engulfed

Cell divides

Cell divides

Activates Activates

Presents antigen toidentify invader andactivates helper T cells

Step 1: Threat

Step 2: Detection

Step 3: Alert

Step 4: Alarm Step 4: Alarm

Step 7: Continuedsurveillance

Cell-mediated response





Naive B cell

Plasma cell

Antibodies

Memory B cell

Secretes


Memory cellsremain and providea quick response tothe antigen in afuture encounter

Cell divides

Activates

Step 4: Alarm


Step 6: Defense

Step 5: Buildingspecific defenses

Pathogens or toxinsoutside of cells

Targets



Figure 13.12 (1 of 2)

Step 4: AlarmThe helper T cell stimulatesthe B cell to begin dividing.

Step 5: Buildingspecific defensesThe B cell divides andforms plasma cells andmemory cells.

Memory B cell

B cell

B cell

B cell

Helper T cell

Plasma cell



Figure 13.12 (2 of 2)


Step 6: DefensePlasma cells secreteantibodies specificfor that antigen.

Step 7: ContinuedsurveillanceMemory B cells remain andmount a quick response ifthe invader is encounteredagain.

Memory B cells

Memory B cell

B cell

Plasma cell

Antibodies

Plasma cell


Cell-Mediated Responses

Cell-mediated immune responses Involve living cells Protect against cellular threats, including

body cells that have become infected and cancer cells




Antigen

Macrophage

Helper T cell


Memoryhelper T cell

Naive B cell Naivecytotoxic T cell


Engulfed

Cell divides

Cell divides

Activates Activates

Presents antigen toidentify invader andactivates helper T cells

Step 1: Threat

Step 2: Detection

Step 3: Alert

Step 4: Alarm Step 4: Alarm







Effectorcytotoxic T cell

Memorycytotoxic T cell

Naivecytotoxic T cell

Memory cellsremain and providea quick response tothe antigen in afuture encounter

Cell divides

Activates

Step 4: Alarm


Step 6: Defense

Step 5: Buildingspecific defenses

Cells infected with intracellularpathogen; cancer cells; cells oforgan transplants

Targets




Figure 13.14 (1 of 2)

Step 5: Building specificdefensesThe cytotoxic T cell dividesand forms effector cytotoxicT cells and memorycytotoxic T cells. Memory

cytotoxic T cell


Step 4: AlarmThe helper T cell stimulates anaive or memory cytotoxic Tcell to begin dividing.

Helper T cell

Cytotoxic T cell

Antigen

Virus



Figure 13.14 (2 of 2)

Step 5: Building specificdefensesThe cytotoxic T cell dividesand forms effector cytotoxicT cells and memorycytotoxic T cells.

Step 6: DefenseEffector cytotoxic cellscause the target cell toburst and die. In this case,the target cell is a cellinfected with a virus thattriggered the response.

Step 7: ContinuedsurveillanceMemory cytotoxic T cellsremain and mount a quickresponse if the invader isencountered again.

Memory cytotoxic T cells

Memorycytotoxic T cell

Target cell


Perforin

T cell membrane

Target cell membrane

Perforin assemblinginto pores



Table 13.2 (1 of 2)



Table 13.2 (2 of 2)



Table 13.3 (1 of 2)



Table 13.3 (2 of 2)



Animation—Antibody- and Cell-Mediated ImmunityPLAY


Immune Response Steps

1. Threat Foreign cell or molecule enters the body

2. Detection Macrophage detects foreign cell or

molecule and engulfs it



3. Alert Macrophages present antigens to helper

T- cells to trigger an immune response They are called antigen-presenting cells



Figure 13.10



4. Helper T cells activate B cells and T cells to destroy the specific antigen When activated, these cells divide to form

clones of cells designed to eliminate a specific antigen from the body



Figure 13.11 (1 of 2)

The selected B celldivides, producing aclone of cells all bearingreceptors specific forthat particular antigen.

The antigen binds to theB cell with appropriatereceptors.

This B cell hasreceptors specificfor this particularantigen.

There is atremendousvariety of B cells.Each B cell hasreceptors for adifferent antigenon its surface.

Antigen

B cells

B-cellreceptorreceptor



Figure 13.11 (2 of 2)

Plasma cells produceantibodies specific forthis particular antigen.

Memory cells remainto bring about a quickresponse to thatantigen in the future.

The selected B celldivides, producing aclone of cells all bearingreceptors specific forthat particular antigen.

Plasmacells

Memory cells



5. Specific defense mechanism is built B cells form plasma cells that secrete

antibodies into the bloodstream that bind to antigens

T cells form cytotoxic T cells that attack



Figure 13.12 (1 of 2)

Step 4: AlarmThe helper T cell stimulatesthe B cell to begin dividing.


Memory B cell

B cell

B cell

B cell

Helper T cell

Plasma cell



Figure 13.12 (2 of 2)


Step 6: DefensePlasma cells secreteantibodies specificfor that antigen.

Step 7: ContinuedsurveillanceMemory B cells remain andmount a quick response ifthe invader is encounteredagain.

Memory B cells

Memory B cell

B cell

Plasma cell

Antibodies

Plasma cell



6. Primary defense Antibodies specific to the antigen eliminate

the antigen Cytotoxic T cells release perforins that

cause cells with the antigen to burst



Immunoglobulins Five classes of antibodies, each with a

special role to play in protecting against invaders IgG IgM IgE IgA IgD



Figure 13.13



Table 13.4



7. Immunological memory Allows for a more rapid response on

subsequent exposure to the antigen Primary response may be slow as the

antibody concentration rises Secondary response is strong and swift

due to the large number of specific memory cells that can respond to the antigen



Figure 13.15



8. Suppressor T cells Turn off the immune response when the

antigens no longer pose a threat


Active Immunity

Active immunity The body actively participates by producing

memory B cells and T cells following exposure to an antigen

This process can also happen through vaccination

Because memory cells are produced, active immunity is relatively long lived


Passive Immunity

Passive immunity Results when a person receives antibodies

that were produced by another person or animal

Short lived since the recipient’s body was not stimulated to produce memory cells


Monoclonal Antibodies

Monoclonal antibodies A group of identical antibodies that bind to

one specific antigen Used in research, clinical diagnosis, and

disease treatment because they can help diagnose certain diseases in their early stages


The Immune System Can Cause Problems

Autoimmune disorders Failure to recognize distinguish between self

and nonself Occur when the immune system attacks the

body’s own cells


The Immune System Can Cause Problems

Figure 13.16


Immune System Problems

Allergies Immune responses to harmless substances

called allergens Allergens cause plasma cells to release

large numbers of class IgE antibodies



Figure 13.17



Table 13.6



These IgE class antibodies bind to mast cells or basophils, causing them to release histamine

The histamine causes redness, swelling, itching, and other symptoms of an allergic response



Figure 13.18 (1 of 2)Mast cell

Plasma cell

Allergen

IgE antibody

Granulescontaininghistamine

First exposure

Step 1: The invader (allergen)enters the body.

Step 2: Plasma cells producelarge amounts of class IgEantibodies against theallergen.

Step 3: IgE antibodies attachto mast cells, which are foundin body tissues.



Figure 13.18 (2 of 2)

Subsequent (secondary) response

Antigen

Histamine

Step 4: More of the sameallergen invades the body.

Step 5: The allergencombines with IgE attachedto mast cells. Histamine andother chemicals are releasedfrom mast cell granules.

• Histamine stimulates releaseof large amounts of mucus.

• Histamine causes smoothmuscle in walls of air tubulesin lungs to contract.

Step 6: Histamine causesblood vessels to widen andbecome leaky. Fluid entersthe tissue, causing swelling.



Antihistamines are most effective in reducing the allergy symptoms



Allergy shots inject increasing amounts of a known allergen in an effort to desensitize the person to the offending allergens

Susan Capasso, Ed.D., CGC St. Vincent’s College Suggested Lecture Presentation Copyright © 2009...

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