Immune System and DiseaseChapter 31

Louis Pasteur and His Germ Theory

in the 1850s, Pasteur proposed that specific microorganisms caused diseases.

He called these disease-causing agents PATHOGENS.

Pasteur’s Germ theory was NOT immediately accepted and took the work of TWO other scientists to validate his own work.

Section 1

Support for Pasteur’s Germ Theory

British surgeon Joseph Lister’s patients died from infection after successful operations about 50% of the time.

When he heard about the germ theory, he began using a weak acid to clean his tools and patient's wounds before and after surgery and his death from infection rte dropped to nearly 0.

German scientist Robert Koch found out that he could make a healthy animal sick with the pathogens from a sick animal.

He established set steps to cultivate the pathogen in an isolated culture and would from the sick animal, and then give the cultured pathogen to the healthy animal and watch it get sick every time.

He also said the pathogen had to be re-cultivated from the newly sicked animal and showed that it was exactly the same as the one he put in.

Different types of Pathogens

Bacteria – single celled organisms, cause illness by releasing chemicals that are toxic to the host or by destroying healthy body tissue.

Viruses – disease causeing strands of DNA or RNA that are surrounded by protein coats. (couldn’t be seen until 1930s!)

Fungi – can be multi or single-cellular, cause disease by piercing healthy cells and steeling their nutrients. Fungal infections usually occur in places that are warm and damp.

More pathogens Protozoa – single-celled

organisms that prey on other cells. ex Malaria

Parasites – organisms that grow and feed on a host

The Immune SystemChapter 31 Section 2

immune cell fighting pathogens….

Castle vs The Immune System

Tall outer walls to keep enemies out.

Has windows and doors to allow certain things in, but the bad guys can sneak through so they have body guards.

Your skin acts as the wall that protects your insides. Skin also secrets sweat and oils that makes the service slightly acidic which some pathogens cannot survive on.

Eyes, ears, nose, mouth, and excretory openings which need extra protection… mucus membranes to trap pathogens.

Once inside the body….

Just like the castle guard who sounds the alarm……

The immune systems must rely on the circulatory system to send chemical signals to coordinate the attack and to transport specialized cells to the infection.

Cells and Proteins = Your Body’s Warriors White Blood Cells- find and kill pathogens that have gotten past

the body’s external barriers. see figure 31.6 page 946 *know for test!

When pathogens enter the body, basophils in the blood stream or mast cells found in other tissues, release chemical signals.

These signals attract other WBC’s to the site to help in the fight.

If the pathogen is a virus, bacterium, or fungus, NEUTROPHILS AND MACROPHAGES go to work.

If the pathogen is a parasite, EOSINOPHILS come and spray it with poision.

Warrior cells in action If the pathogen is a parasite,

EOSINOPHILS come and spray it with poison.

If the pathogen is a virus, bacterium, or fungus, NEUTROPHILS AND MACROPHAGES go to work.

Neutrophils and macrophages are PHAGOCYTES… cells that destroy pathogens by surrounding and engulfing them.

Warrior cell action cont.

After the phagocytes, the lymphocytes reach the infection.

These are WBCs that initiate specific immune responses.

TWO TYPES: T cells-(aka T lymphocytes) destroy body cells that are infected

with pathogens B cells- (aka B lymphocytes) produce proteins that inactivate

pathogens that have not yet infected a body cell.

Proteins used by the immune system

Complement proteins = used by WBCs and certain organs. a. weaken the pathogen’s cell membrane so H2O can enter and cause it to

burst b. attract phagocytes to the infected area c. cause the pathogen to stick to the walls of blood vessels to make them

easier to be found by circulating phagocytes

Antibodies= proteins made by B cells. destroy pathogens by: a. binding to the pathogen’s membrane proteins b. causing pathogens to clump to make easier to engulf c. activate compliment proteins that weaken the pathogen’s cell membrane.

Interferons = proteins produced by body cells that are infected by a virus. these proteins stimulate near by uninfected cells to produce enzymes that will prevent the virus from entering and infecting them. Other interferons stimulate inflammation response. (swelling)

Immunity Passive immunity – occurs when the body’s

undergoing an immune response. Transferred from one generation to the next from mother to child.

Active immunity – your body produces in response to a specific pathogen that HAS infected or is infecting your body. Acquired immunity is a type of active

immunity that occurs once your body has responded to a pathogen ex. chicken pox

Section 3 Immune Responses

The body responds to pathogens and foreign particles with SPECIFIC and NONSPECIFIC responses. Responses that occur at the cellular level are called

SPECIFIC responses and will vary its reaction to different stimuli.

Non-specific responses that react the same way to every stimulus.

Non-Specific Responses:

INFLAMMATION characterized by swelling, redness, pain, itching, and increased

warmth at the affected site. Will occur when a pathogen enters the body or the body’s

tissues become damaged.

The response begins when mast cells or basophils release chemicals called histamines in response to a pathogen invasion. Histamines cause the blood vessel walls to spread out this allows WBCs to squeeze out of the capillary and towards the

site of infection to help fight off the pathogen

Non-specific: FEVER Develop when mast cells or MACROPHAGES release

chemicals that cause the hypothalamus to increase the body’s temperature.

Once the infection is under control, the mast cells will stop producing the chemicals and the body temp will return to normal.

Low fevers (100 degree F) help speed the destruction of the pathogens

HIGH FEVERS (103+) can be very dangerous since the hypothalamus is no longer in control, seizure, brain damage, or even death can occur.

Connect Question….

Q: What body systems, other than the immune system, help to produce

inflammation and fever???A: nervous and circulatory

Specific responses

Specific immune responses begin with the detection of antigens. Antigens are surface

proteins on pathogens. Each pathogen has a

different antigen.

Immune Responses

Two types of Immune Response that produce acquired immunity: Cellular immune response humoral immune response

Immunity is acquired when the body produces memory cells after fighting off an infection.

Memory cells are specialized T and B cells that “remember” an antigen that has previously invaded allowing the body to recognize it and destroy it the next time prior to the body becoming sick.

Cellular immunity: depends on T cells. The T cells attach to infected body cells and cause them to

burst only after they have been activated. (see page 952)

HOW TO BECOME AN ACTIVATED T CELL

1. A phagocyte recognizes a foreign invader and engulfs it, removes its antigens and displays them on its cell membrane. (this is called the antigen-presenting cell)

2. A T cell encounters the APC and binds to it. The APC cell releases proteins to activate the T cell.

3. Once activated, the T cell will divide and differentiate into two different types of T cells: activated and memory. The activated fight and the memory act as the reserves.

4. The activated T cells bind and destroy infected body cells.

Humoral Immunity depends on antibodies that either fight the pathogen causing them to burst,

inactivating the pathogen, or causing them to clump. (see page 253)

The steps to Humoral Immunity

1. A pathogen binds to a B cell. The B cell engulfs it and puts part of the antigens on its own surface.

2. A T cell meets a APBcell, binds to it and releases proteins to activate the B cell.

3. The activated B cell divided and differentiates into activated B cells and memory cells.

4. Activated B cells produce as many as 2000 pathogen specific antibodies per second.

(these can cause the pathogen to clump)

5. Phagocytes engulf and destroy the pathogen clumps.

Foreign tissues

All cells have protein markers on their surfaces.

Your body is constantly deciding if your cells are your own or foreign.

Tissue rejection occurs when the recipient’s immune system makes antibodies against the protein markers on the donor’s tissue.

Autoimmune diseases are caused when the body no longer recognizes its self as self and destroys its own tissues.