the body’s defenses chapter 43. fig. 43-7 adenoid tonsil lymph nodes spleen peyer’s patches...

The Body’s Defenses

Chapter 43

Fig. 43-7

Adenoid

Tonsil

Lymphnodes

Spleen

Peyer’s patches(small intestine)

Appendix

Lymphaticvessels Lymph

nodeMasses ofdefensive cells

Bloodcapillary

Lymphaticvessel

Tissuecells

Interstitial fluid

Pathogen

• Pathogen: An agent of disease. A disease producer. The term pathogen most commonly is used to refer to infectious organisms. – These include bacteria

(such as staph), viruses (such as HIV), and fungi (such as yeast).

– Less commonly, pathogen refers to a noninfectious agent of disease such as a chemical.

Fig. 43-1

1.5 µm

Fig. 43-2

INNATE IMMUNITY

Recognition of traitsshared by broad rangesof pathogens, using asmall set of receptors

•

•Rapid response

•Recognition of traitsspecific to particularpathogens, using a vastarray of receptors

•Slower response

ACQUIRED IMMUNITY

Pathogens(microorganisms

and viruses)

Barrier defenses:SkinMucous membranesSecretions

Internal defenses:Phagocytic cellsAntimicrobial proteinsInflammatory responseNatural killer cells

Humoral response:Antibodies defend againstinfection in body fluids.

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

• First Line of Defense

• Second Line of Defense

• Third Line of Defense

1st line of Defense

• Nonspecific Barrier– Skin– Mucous

• Lysozyme

– Cilia– Stomach Acid

2nd Line of Defense

• 1st line has been penetrated!!!

– Inflammatory Response• Vasodilation

– Histamine» Released by: Basophils & Mast Cells

– Prostaglandins – Promotes Blood Flow– Chemokines – attracts phagocytes

» Neutrophils destroy microbes» Monocytes into Macrophages large # of

microbes– Pyrogens – increases temperature– Interferons – block against viral infections

3rd Line of Defense

• Specific Response

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Acquired immunity defends against infection of body cells and fluids

• Acquired immunity has two branches: the humoral immune response and the cell-mediated immune response

• Humoral immune response involves activation and clonal selection of B cells, resulting in production of secreted antibodies

• Cell-mediated immune response involves activation and clonal selection of cytotoxic T cells

• Helper T cells aid both responses

Fig. 43-16

Humoral (antibody-mediated) immune response

B cell

Plasma cells

Cell-mediated immune response

Key

Stimulates

Gives rise to

+

+

++

+

+

+Memory B cells

Antigen (1st exposure)

Engulfed by

Antigen-presenting cell

MemoryHelper T cells

Helper T cell Cytotoxic T cell

MemoryCytotoxic T cells

ActiveCytotoxic T cells

Antigen (2nd exposure)

Secretedantibodies

Defend against extracellular pathogens by binding to antigens,thereby neutralizing pathogens or making them better targetsfor phagocytes and complement proteins.

Defend against intracellular pathogensand cancer by binding to and lysing theinfected cells or cancer cells.

+

+ +

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Active and Passive Immunization

• Active immunity develops naturally in response to an infection

– It can also develop following immunization, also called vaccination

• Passive immunity provides immediate, short-term protection

– Breast Milk

– Injection of Antibodies

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings