1. Kuby Immunology, 7e: Chapter 1
Overview of the Immune System

2. A historical perspective of immunology
What is immunity?
Immunity is the state of protection against foreign pathogens or substances (antigens)
Latin term immunis, meaning “exempt,” is the source of the English word immunity
Observations of immunity go back over 2000 years
Thucydides, an ancient historian, wrote in 430 bc of a plague in Athens where those who had recovered could safely nurse the currently ill

3. A historical perspective of immunology
Can we generate immunity without inducing disease? YES…through vaccination
Vaccination prepares the immune system to eradicate an infectious agent before it causes disease
Widespread vaccine use has saved many lives
Classic examples: rabies vaccine and eradication of smallpox

5. A historical perspective of immunology
A portion of immunity involves both humoral and cellular components
Humoral immunity combats pathogens via antibodies
Antibodies are produced by B cells
Antibodies can be transferred between individuals to provide passive immunity
Cell-mediated immunity involves primarily T lymphocytes
These can eradicate pathogens, clear infected self-cells, or aid other cells in inducing immunity

6. A historical perspective of immunology
Clonal selection
Individual B and T cells each have an individual specificity for a single antigen
This is due to each cell having many copies of a receptor on their surface that only bind to one type of antigen
When a B or T cell interacts with its specific antigen, it is selected and becomes activated
Activation results in a proliferation, producing a large number of clones
Each clone is reactive against the antigen that initially stimulated the original lymphocyte

8. Important concepts for understanding the mammalian immune response
Pathogens fall into four major categories
Immune responses are quickly tailored to the type of organism involved

10. Important concepts for understanding the mammalian immune response
Immune responses rely on recognition molecules
Germ-line encoded (pattern recognition receptors, PRRs)
These bind to pathogen-associated molecular patterns (PAMPs)―generic molecules found on many different types of pathogens (e.g., peptidoglycan)
Randomly generated (B and T cell receptors)
These bind to very specific antigens, rather than generic molecules found on many pathogens

11. Important concepts for understanding the mammalian immune response
Humoral and cell-mediated immunity relies on surface receptors (B and T cell receptors)
These are randomly generated by DNA rearrangements in B and T cells
Many of these are nonviable and are deleted during development

13. Important concepts for understanding the mammalian immune response
Tolerance ensures that the immune system avoids destroying host tissue
Many of the random rearrangements used to create B and T cell receptors could be anti-self
Tolerance helps to keep these anti-self recognition molecules/cells from circulating in the bloodstream

14. Important concepts for understanding the mammalian immune response
In response to pathogens, vertebrate immune systems use two interconnected systems
Innate immunity
Adaptive immunity

15. Important concepts for understanding the mammalian immune response
Innate immune responses
First line of defense
Fast, but nonspecific
Uses germ-line–encoded recognition molecules
Also uses phagocytic cells

16. Important concepts for understanding the mammalian immune response
Adaptive immune responses
Humoral and cell-mediate responses
Using B and T lymphocytes, respectively
Slower to develop
5–6 days (or more)
Use randomly generated antigen receptors
Highly specific to individual antigen molecules

17. Important concepts for understanding the mammalian immune response
Innate and adaptive immunity work cooperatively
Activation of innate immune responses produces signal molecules (often cytokines)
These signal molecules stimulate and direct adaptive immune responses

18. Important concepts for understanding the mammalian immune response
Memory is the hallmark of adaptive immunity
Primary response is initiated upon first exposure to an antigen
Memory lymphocytes are left
behind after antigen is cleared
A second exposure to the
same antigen re-stimulates
memory lymphocytes
Reactivation yields faster,
more significant, better response
Memory is NOT present in
innate immunity

19. The good, bad, and ugly of the immune system
Dysfunctions of immunity―two broad categories
Overly active or misdirected immune responses
Allergies/asthma
Autoimmune disease (e.g., multiple sclerosis,
Crohn’s disease)
Immunodeficiency
Primary (genetic) loss of immune function
Secondary (acquired) loss of immune function
Opportunistic infections (e.g., oral thrush) can occur in people with impaired immune responses

20. The good, bad, and ugly of the immune system
Transplanted tissues
A rare case where we want to AVOID an immune response (rejection)
The body’s natural response to foreign tissue is to attack it and destroy it
Cancer
A situation where the dangerous cells we want to target are our own self cells
Generally tolerated and hard to generate immunity against

21. Summary
Immunity is a complex subject, broken down into many different layers and areas
This is just a quick summary of the basics of the field―there’s MUCH more to come!
Understanding how immunity works allows us to:
Exploit it to prevent infections (vaccination)
Exploit it to treat illness (shutting down autoimmune disease or ramping up anti-cancer responses)
Provide safer organ and tissue transplants