1. Biology 212 Anatomy & Physiology I
Body Defenses

2. Body Defenses:
Homeostasis: Protects body against foreign organisms, toxins, chemicals, damaged cells & tissues, etc.
Two forms:
- Nonspecific defenses
- Specific defenses

3. Nonspecific Body Defenses - First line defenses
Epithelial Barriers: Skin, cornea, mucous membranes
Phagocytes: Macrophages, neutrophils, eosinophils
Antimicrobial chemicals:
Acids - stomach, vagina, urethra
Lysozyme: polysaccharide, binds to & destroys bacterial
cell walls
Complement: proteins, bind to bacteria & parasites
- directly lyse them
- mark them for phagocytes
Interferons: proteins, prevent viruses from infecting cells &
mark virus-infected cells for phagocytes

4. Nonspecific Body Defenses - Second lines of defense after
foreign material enters tissues
Fever

5. Nonspecific Body Defenses - Second lines of defense after
foreign material enters tissues
Fever
Inflammation: Inflammatory chemicals from damaged tissues
Vasodilation
Pain
Increased capillary permeability
Swelling
Increased oxygen
Attraction of leukocytes: macrophages
lymphocytes
neutrophils
eosinophils
basophils

6. Nonspecific Body Defenses - Second lines of defense after
foreign material enters tissues
Fever
Inflammation

7. Specific or Immune Defenses
- Specific: Provides defense against specific molecules
(antigens) recognized as "non-self"
- Adaptive: Defenses can be targeted against new antigens
- Systematic: Defenses are distributed through entire body,
not limited to site of infection
- Memory: Mounts stronger and faster defense against
previously encountered antigens
The immune system must also develop Self-Tolerance: It must not respond to the body’s own cells & molecules

8. Terminology
Pathogen: Any organism (e.g. bacterium, virus, parasite)
against which the immune system responds
Antigen: Any molecule against which the immune system
responds: May be isolated molecule
May be part of larger structure
(e.g. protein within a cell membrane)
Antibody: A specific protein, also called immunoglobulin,
which binds to an antigen.
Produced by lymphocytes
Antigenic Determinant or Epitope: The specific part of an
antigen which an antibody recognizes and binds to

10. Five Classes of Antibodies

12. Specific or Immune Defenses
Two inter-related components:
- Cell-mediated immunity
Macrophages and T-lymphocytes
Lymphocytes directly attack invading or damaged cells
- Humoral immunity
Antibodies produced by plasma cells (B-lymphocytes)
(with some help from T-lymphocytes)
Antibodies attach to invading cells or isolated antigens

13. Naturally Artificially Acquired Acquired
Immunity
Naturally Artificially
Acquired Acquired
Active Passive Active Passive
Antigens enter Antibodies pass Antigens Injection of
the body from mother to injected into preformed
naturally by fetus through body through antibodies or
infection or placenta; or vaccination serum which
contact with from mother to with dead contains
pathogen infant in milk or weakened antibodies
Body produces pathogens
antibodies and Body produces
immune cells antibodies and
immune cells

14. Cells of the Immune System:
1. Macrophages:
2. Lymphocytes and the cells into which they mature
3. Other Antigen Presenting Cells

15. Cells of the Immune System:
1. Macrophages:
Engulf and destroy pathogens, damaged cells, etc.
Present antigens to lymphocytes
Secrete Activation Factors

16. Cells of the Immune System:
1. Macrophages:
Engulf and destroy pathogens, damaged cells, etc.
Present antigens to lymphocytes
Secrete Activation Factors
2. Lymphocytes and the cells into which they mature
B - lymphocytes Plasma cells
Memory cells
T - lymphocytes Cytotoxic (killer) cells
Helper cells
Regulatory/Suppressor cells

17. Cells of the Immune System:
1. Macrophages:
Engulf and destroy pathogens, damaged cells, etc.
Present antigens to lymphocytes
Secrete Activation Factors
2. Lymphocytes and the cells into which they mature
B - lymphocytes Plasma cells
Memory cells
T - lymphocytes Cytotoxic (killer) cells
Helper cells
Regulatory/Suppressor cells
Other Antigen Presenting Cells: Reticular cells
Dendritic cells

18. Macrophages in Immunity

19. Lymphocytes in Immunity
Two types:
Both originate in bone marrow
T – Lymphocytes: Become immunocompetent in thymus
Responsible for cell-mediated immunity
B – Lymphocytes: Become immunocompetent in bone
marrow & regions of digestive system
Responsible for humoral immunity
Both reproduce themselves during immune response

20. Humoral Immune Response
Effective against both isolated antigens and cells.
Begins when immunocompetent B-lymphocyte recognizes & binds to a specific antigen,
becoming activated.

22. Antibodies from plasma cells have three actions:
Neutralize the antigen
by changing its shape
Cause antigens or pathogens
to agglutinate or precipitate
Mark the antigen or pathogen
to be phagocytosed
Antibody binding onto an antigen or pathogen also stimulates nonspecific defenses such as inflammation or fever.

23. Cell-mediated Immune Response
Effective against invading cells or damaged cells
Begins when macrophage or infected cell presents antigen to immunocompetent T-lymphocytes, activating them
When cytotoxic T-lymphocyte activated, it binds to target cell & releases molecules which directly damage it, e.g. perforin, lymphotoxins, tumor necrosis factor, oxygen-free-radicals

24. Cell-mediated Immune Response
Effective against invading cells or damaged cells
Begins when macrophage or infected cell presents antigen to immunocompetent T-lymphocytes, activating them
When helper T-lymphocyte activated, it secretes chemicals which activate macrophages and stimulate proliferation of both B- and cytotoxic T-lymphocytes

25. Cell-mediated Immune Response
Third type, regulatory or suppressor T-lymphocytes, secrete chemicals which suppress the activities of both T- & B-lymphocytes.
Necessary to “wind down” immune response after antigen or invading/damaged cell destroyed
Minimizes risk of cross-reactivity and damage to “self” cells (autoimmune diseases)
Help convert activated T- & B-lymphocytes to memory cells