1. The Body’s Defenses
Chapter 43

2. Interstitial fluid Adenoid Tonsil Blood capillary Lymph nodes Spleen
Fig. 43-7
Interstitial fluid
Adenoid
Tonsil
Blood
capillary
Lymph
nodes
Spleen
Tissue
cells
Lymphatic
vessel
Peyer’s patches
(small intestine)
Appendix
Figure 43.7 The human lymphatic system
Lymphatic
vessels
Lymph
node
Masses of
defensive cells

3. 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.

4. Fig. 43-1
Fig 43.1 How do immune cells of animals recognize foreign cells?
For the Cell Biology Video Leukocyte Adhesion and Rolling, go to Animation and Video Files.
1.5 µm

5. First Line of Defense Second Line of Defense Third Line of Defense
Fig. 43-2
Pathogens
(microorganisms
and viruses)
INNATE IMMUNITY
Barrier defenses:
Skin
Mucous membranes
Secretions •
Recognition of traits
shared by broad ranges
of pathogens, using a
small set of receptors
First Line of Defense
Second Line of Defense
Third Line of Defense
Internal defenses:
Phagocytic cells
Antimicrobial proteins
Inflammatory response
Natural killer cells •
Rapid response
ACQUIRED IMMUNITY
Humoral response:
Antibodies defend against
infection in body fluids.
Figure 43.2 Overview of animal immunity •
Recognition of traits
specific to particular
pathogens, using a vast
array of receptors
Cell-mediated response:
Cytotoxic lymphocytes defend
against infection in body cells. •
Slower response

6. 1st line of Defense Nonspecific Barrier Skin Mucous Cilia Stomach Acid
Lysozyme
Cilia
Stomach Acid

7. 2nd Line of Defense Inflammatory Response
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

9. 3rd Line of Defense
Specific Response

10. 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

11. Figure 43.16 An overview of the acquired immune response
Humoral (antibody-mediated) immune response
Cell-mediated immune response
Key
Antigen (1st exposure) +
Stimulates
Gives rise to
Engulfed by
Antigen-
presenting cell + + +
B cell
Helper T cell
Cytotoxic T cell + +
Memory
Helper T cells + + +
Figure An overview of the acquired immune response
Antigen (2nd exposure) +
Memory
Cytotoxic T cells
Active
Cytotoxic T cells
Plasma cells
Memory B cells
Secreted
antibodies
Defend against extracellular pathogens by binding to antigens,
thereby neutralizing pathogens or making them better targets
for phagocytes and complement proteins.
Defend against intracellular pathogens
and cancer by binding to and lysing the
infected cells or cancer cells.

12. 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