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