1. The Body’s Defenses: The Immune System
Chapter 43
Part II

2. Two ways to fight Innate immunity Acquired immunity
Defense before any exposure to pathogen
Acquired immunity
Defense builds in response to present pathogen

3. Specific Defenses
When nonspecific defense mechanisms are unable to prevent infection, the immune defense system is activated
Product of immune system that is:
Specific
Diverse
Recognizes self/non-self
Able to remember
May require several days to become fully activated
Deploys extremely powerful cellular and chemical weapons
Two types of specific defense:
Cell-mediated
Humoral

4. 1. Specificity Response is not random
Recognize and eliminate particular pathogens
Body responds to antigen by releasing antibody

5. Antigens Anything that elicits an immune response
Usually a foreign protein
Example: a cat and its dander, an allergen/antigen for many people

6. Antibodies
Proteins secreted by B cells in response to antigen presence
Specific antibodies are produced for each antigen type

7. 2. Diversity
The variable region (V) is different for each antigen!

8. 3. Self/Non-self Recognition
Blood groups, tissue grafts, and organ transplants
Autoimmune disorders – recognition failure
Major histocompatibility complex (MHC)
Unique proteins embedded in plasma membrane
Class I
Cytotoxic T cells
Class II
Helper T cells

9. 4. Memory Memory cells survive in system for a long period of time
Activated during secondary immune response

10. Immune System Response
The immune system responds in 3 essential steps:
Recognition of the invader (caught on the radar!)
Activation of the system (man your battle stations!)
Response to the invader (fire all weapons!)

11. Once the immune system has been activated…
The response can be in the form of:
Antibodies (humoral)
Lyphocytes (cell-mediated)

12. Humoral Immunity Activation and clonal selection of B cells
Secretion of antibodies to circulate and defend against specific antigens
Memory cells for secondary response later

13. Cell-Mediated Immunity
Activating and clonal selection of cytotoxic T cells
Destruction of specific target cells
Memory cells for secondary response later

15. Immune System More specific than nonspecific methods
Memory improves response time when an invader is again encountered
Immunity can be conferred passively or actively

16. Passive Immunity Transferred from one individual to another
Antibodies in mother’s milk
Antibodies can be given to adults as well
Temporary, jump-start to immunity
Work long enough to prevent infection

17. Active Immunity
Immunity acquired through individual’s own immune response
Catching a disease
Vaccinations
Stimulate antibody production and formation without causing the disease
Made from killed pathogens or weakened strains

18. Passive vs. Active Immunity

19. Autoimmune Diseases
Immune system turns against beneficial molecules in the body
Ex: lupus
Antibodies break down histones

20. Immunodeficiency Diseases
Inability of immune system to protect the body
Ex: AIDS
Inability to produce T cells
Can’t stop HIV