Chapter 43: Immune System

Learning Targets1. I can explain innate immunity by:

Describing barrier defenses Describing internal defenses

2. I can explain adaptive immunity by:describing humoral response which includes:

B cells Plasma cells Antibodies Memory cells Helper T cells

Describing cell mediated response which includes Cytotoxic T Cells and memory cells

3. I can identify and explain parts of immune system that represent how cells communicate via paracrine communication.

4. I cam explain the difference between a primary and secondary immune response

5. I can explain the difference between active and passive immunity.

Focus Questions

1. What is the functional difference between cell mediated and humoral immunity? Why do we have both types?

2. Which blood cells are involved in cell mediated immunity?

3. Which blood cells are involved in humoral immunity?

4. Why is it that you don’t get the chicken pox, once you have already had it?

5. If you are bit by a venomous snake, what type of immunity are you given when you receive an anti venom injection? When you received your hepatitis vaccination, what type of immunity are you given?

Figure 43.2

Pathogens(such as bacteria,fungi, and viruses)

INNATE IMMUNITY(all animals)

• Rapid response

Recognition of traits sharedby broad ranges ofpathogens, using a smallset of receptors

•

Recognition of traits specific to particularpathogens, using a vastarray of receptors

•

• Slower response

Barrier defenses:SkinMucous membranesSecretions

Internal defenses:Phagocytic cellsNatural killer cellsAntimicrobial proteinsInflammatory response

Humoral response:Antibodies defend againstinfection in body fluids.

Cell-mediated response:Cytotoxic cells defendagainst infection in body cells.

ADAPTIVE IMMUNITY(vertebrates only)

Figure 43.15

Primary immune responseto antigen A producesantibodies to A.

Secondary immune response toantigen A produces antibodies to A;primary immune response to antigenB produces antibodies to B.

Exposureto antigen A

Exposure to antigens A and B

Time (days)

An

tib

od

y co

nce

ntr

atio

n(a

rbit

rary

un

its)

104

103

102

101

100

0 7 14 21 28 35 42 49 56

Antibodiesto A

Antibodiesto B

Cell mediated Immunity

Antigen-presentingcell

Pathogen

Antigen fragment

Class II MHC moleculeAccessory proteinAntigen receptor

Helper T cell

Cytokines

Humoralimmunity

Cell-mediatedimmunity

B cellCytotoxic T cell

3

2

1

Figure 43.17-1

Cytotoxic T cell

1

Accessoryprotein

Class I MHCmolecule

Infectedcell

Antigenreceptor

Antigenfragment

Figure 43.17-2

Cytotoxic T cell

1 2

Accessoryprotein

Class I MHCmolecule

Infectedcell

Antigenreceptor

Antigenfragment

Perforin

Pore

Gran-zymes

Figure 43.17-3

Cytotoxic T cell

31 2

Accessoryprotein

Class I MHCmolecule

Infectedcell

Antigenreceptor

Antigenfragment

Perforin

Pore

Gran-zymes

ReleasedcytotoxicT cell

Dyinginfected cell

Humoral Response

Pathogen

1

Antigen-presentingcell Antigen

fragment

Class IIMHC

molecule

Antigenreceptor

Accessoryprotein

Helper T cell

Humoral Response

Pathogen

1 2

Antigen-presentingcell Antigen

fragment

Class IIMHC

molecule

Antigenreceptor

Accessoryprotein

Helper T cell

B cell

Cytokines

Activatedhelper T cell

Humoral Response

Pathogen

31 2

Antigen-presentingcell Antigen

fragment

Class IIMHC

molecule

Antigenreceptor

Accessoryprotein

Helper T cell

B cell

Cytokines

Activatedhelper T cell

Memory B cells

Plasma cellsSecreted

antibodies

Figure 43.19

OpsonizationNeutralization

Antibody

VirusBacterium

Macrophage

Activation of complement system and poreformation

Complement proteins

Formation of membraneattack complex

Flow of waterand ions

Pore

AntigenForeigncell

Figure 43.20

Humoral (antibody-mediated) immune response Cell-mediated immune response

Antigen (1st exposure)

Engulfed by

Antigen-presenting cell

Helper T cell

Memoryhelper T cells

Antigen (2nd exposure)

B cell

Plasma cells

Secretedantibodies

Defend against extracellularpathogens

Memory B cellsMemory

cytotoxic T cellsActive

cytotoxic T cells

Defend against intracellularpathogens and cancer

Cytotoxic T cell

Key

Stimulates

Gives rise to

Figure 43.UN02Stem cell

Cell division andgene rearrangement

Elimination ofself-reactiveB cells

Clonalselection

Antigen

AntibodyFormation ofactivated cellpopulations

Memory B cells Plasma cells

Pathogen

Receptors bind to antigens

Figure 43.UN03