1. Pre-AP Biology Chapter 40-2
Immune System
Pre-AP Biology
Chapter 40-2

2. Immune System Overview
Function: fight infection through the production of [specialized] cells that inactivate foreign substances or cells
It is main defense against pathogens
Recognizes, attacks, destroys, and “remembers” each type of pathogen that enters the body
2 general categories:
Nonspecific defenses (fortress walls of the body)
Specific defenses (security guards of the body)

3. Nonspecific Defenses First line of defense: skin
Most important nonspecific defense!
Very few pathogens can penetrate the skin
Must have an opening – a cut, scratch, mouth, nose
Mucus, saliva, and tears have lysozyme – enzyme that breaks down bacteria’s cell wall
Oil and sweat glands produce acidic environment
Mucus and cilia in nose and throat trap and push pathogens away from lungs
Acid and enzymes destroy bacteria that make it to your stomach

4. Nonspecific Defenses Second line of defense: inflammatory response
Reaction to tissue damage caused by injury/infection
When pathogens are detected:
White blood cells flood area through blood vessels near wound
Many WBC are phagocytes – engulf and destroy
Releases chemicals that increase core body temperature (fever)
Many pathogens only survive in narrow temp. range
Increased temp also increases heart rate = more WBC

5. Inflammatory response

6. Nonspecific Defense to Viruses
Sometimes, virus-infected cells produce a group of proteins that help other cells resist infection: Interferons
Named this because they “interfere” with growth of the virus
Slows the progress of infection and gives specific defense system time to respond

7. Specific Defenses Called “immune response” Triggered by antigens
2 types of lymphocytes
B lymphocytes (B cells) – work in body fluids
Humoral immunity
T lymphocytes (T cells) – work in living cells
Cell-mediated immunity

8. Humoral Immunity B cells detect pathogen and multiply rapidly
Produces large numbers of plasma cells and memory B cells
Plasma cells release antibodies (proteins that recognize and bind to antigens – recall blood types!)
Antibodies carried in the blood stream to attack
Memory B cells remain capable of producing antibodies specific to that pathogen after exposure

10. Antibody Structure
Antibody is shaped like a “Y” and has two identical antigen binding sites
Differences in amino acids affect shape of binding sites
Shape of binding site is how antibody recognizes antigen
Healthy adult can produce about 100 million different types of antibodies!

11. Cell-Mediated Immunity
Primary defense against own cells when cancerous or infected
Also important for fighting fungi and protists
Process: T cells divide and differentiate into…
Killer T cells – destroy bacteria, fungi, protozoan or foreign tissue with the antigen
Helper T cells – produce memory T cells
Suppressor T cells – shut down killer T cells after pathogenic cells brought under control
Memory T cells – cause response if same antigen enters again

12. Yellow objects are killer T cells attaching cancer cell (SEM)

13. Transplants Killer T cells make organ transplants difficult
Recognize new organ as foreign and attack it
Called “rejection”
To prevent rejection, donor should have cell markers nearly identical to recipient; and
Recipient usually takes drugs for the rest of their life to suppress cell-mediated immune response.

14. Acquired Immunity Remember Jenner’s smallpox??
Cowpox infection to create immunity to smallpox
Can be active or passive

15. Active vs. Passive Immunity
Type of immunity produced by reaction to a vaccine
Vaccination: injection of weakened or mild form of pathogen
Stimulate immune system to create plasma cells
Plasma cells are ready to make specific antibodies
Appears AFTER exposure
Can be natural or deliberate
Antibodies produced by other animals injected into the bloodstream
Lasts for short time – body eventually destroys them
Can be natural or deliberate
Natural: from mother to fetus or in breastmilk
Deliberate: vaccine
Tropical diseases
Rabies