1. The Immune System
the bad guys
The good guys

2. VIRUSES
The essential design : A core of nucleic acid wrapped in a protein coat.
Variation: due to the different proteins that make up the viral coat
Not Alive: a virus lacks cell‘machinery’ therefore requires a host cells in order to make proteins, reproduce, etc.

3. Ex: BACTERIOPHAGE –attacks bacteria

4. Ex: HIV; INFLUENZA
These have an additional layer - the envelope – surrounding the protein coat

5. Viral reproduction, v1
THE LYTIC CYCLE
Virus enters host, destroying host DNA.
Replicates self like mad, until cell bursts releasing 100’s of new viruses, ready to invade more host cells.

6. Virus enters cell, incorporates its DNA/RNA host DNA
Viral reproduction, v2
The LYSOGENIC CYCLE
Virus enters cell, incorporates its DNA/RNA host DNA
Host cells lives, producing more viral DNA/RNA as it divides
Virus lives on in host for life with periodic outbreaks
The original recombinant DNA!

7. A VIRUS CAN MOVE from the lysogenic to the lytic cycle
ex: Herpes viruses are for life, but only occasional outbreaks

8. Non-Specific (Innate) Immunity
DEFENDERS OF LIFE!
Non-Specific (Innate) Immunity
Always ready; immediate
• 1st line of defense: barriers
• 2nd line of defense: internal
Specific/Acquired
Response to a specific pathogen
• 3rd line of defense: B cells, killer T cells, memory cells
The good guys

9. Barriers to Entry • Skin outer layer dead cells oil/sweat glands
• Mucus & Cilia (hairs)
traps pathogens
induces cough, sneeze
• Antiseptic Body Fluids
Saliva, tears, stomach acid
contain enzymes that breakdown pathogens
non-functional
pathogen
enzyme

10. Second Line of Defense Once the pathogen gets in
Macrophages - white blood cells (WBC) ingest & kill pathogen via phagocytosis
Video
• Inflammatory Response
Injured cells release histamines, causing capillaries to expand (red, hot, swollen) so WBC can fit through, engage pathogen/antigen
Fever
temperature increase is harmful to cells. But too hot and your cells are damaged too

11. Third Line of Defense: Acquired/Specific Immunity
Tailored to each pathogen
Creates an immunological‘memory’
Two routes: Cell mediated & Humoral (antibody)
intracellular pathogens
i.e. most viruses
extracellular pathogens
i.e. bacteria, coated viruses

12. IDENTIFY, DISABLE, and PRESENT
1. Pathogen enters cell
• invades host cell simple virus
• eaten by macrophage bacteria/
coated virus
IDENTIFY, DISABLE, and PRESENT
2. Cell enzymes break down pathogen
host cell/macrophage displays bits (antigens) on cell surface
3. Helper T cells identify and bind to antigens
signal additional immune system cells 3. 1. 2.

13. DECIDE/DIRECT the RESPONSE
Cell-mediated response
Helper T
Humoral (antibody)
Response
Killer (cytotoxic) T cells
B cells
plasma cell
produces memory antibodies cells made
memory cells made
seek & destroy
Antibodies?

14. ANTIBODIES?
Proteins produced to disable extracellular pathogen (bacteria, coated viruses
antibodies
/pathogen
Ex: antibody response to the wrong blood type – it clumps!
Antigen/antibody complex – clumps ‘em up!

15. SOURCES OF ANTIBODIES
Non-specific
specific

16. SINCE IT’S SPRING… DON’T CONFUSE… first exposure every time after
Antibodies and antigens with antibiotics (phew!)
Antibiotics inhibit essential cellular functions a pathogen needs to live or reproduce