How does the body identify and destroy pathogens?

a microorganism such as a virus, bacterium, prion, or fungus, that causes disease in a plant or animal

Infectious Protein◦ No DNA or RNA◦ NOT LIVING

AKA spongiform (like a sponge) encephalopathies (pathogen of the brain)

Mad Cow Disease - Cows Scrapie - sheep Kuru – humans New Guinea,

Has two components◦ Protein covering◦ Nucleic acid (either RNA OR DNA, rarely both)

inside

◦ Infect and “take over” the cell’s replication machinery

◦ Colds, Influenza, HIV

Living prokaryote!

Barriers◦ Separate the organism from its environment

Nonspecific immune response – second l◦ Inflammatory Response◦ Repel and destroy foreign “cells”

Specific immunity◦ How lymphocytes identify and remember certain

types of invasive bacteria, viruses, toxins.◦ Create a “rapid defense system” for any second

attack

Skin Mucous membranes

◦ Secrete mucus (all “openings” to the environment)◦ Mucus contains lysozyme (kills bacteria)

Others◦ Cilia (Resp. system)◦ Stomach acid (low pH kills bacteria)◦ Enzymes (lysozyme in tears)◦ Respiratory tract

◦ Inflammatory Response

◦ Histamine triggers the response Increases the permeability of capillary membranes

(lets white blood cells out of the capillaries)

◦ Phagocytes/macrophages – ingest invaders

◦ Natural Killer cells – lymphocytes that provide a rapid

◦ response to a viral infection.

◦ Help contain a viral infection ◦ while antibodies are being made.

Increased blood flow RESULT: Redness, swelling, pain, warmth,

◦ Clotting (if blood vessel damaged)

Match these to the conditions (next page)

Effects of inflammation Pain Heat Swelling Redness Loss of function (sometimes)

Chronic (long term) inflammation (depending on location

Periodontitis (gums)Atherosclerosis (blood vessels)Crohn’s disease (intestines)Hayfever (respiratory system)Arthritis(joints)

Increase body metabolism , speeding up the repair process (only up to 104 F)

Slow down the reproduction of some bacteria and viruses .

Makes YOU slow down and “rest”

(1) Fever slow down some bacteria and viruses.

(2) Fever increase metabolism (enzymes work faster up to 104 F)

(3) fever makes a patient feel ill, condition which makes the patient more likely to rest.

Complement proteins ◦ Stimulate inflammation and

phagocytosis

Interferon ◦ Send warning signals to neighboring cells◦ Released by a cell which was attacked by a virus

Programmed cell death (apoptosis)

Based on lack of presence of pathogen (foreign antigens)

Signal sent to “self destruct”.

Cells and Tissues that learn about and learn to recognize and attack foreign substances (based on antigen recognition)

Include◦Macrophages(from general response)◦T-cells◦B cells

Cell mediated immune response◦ Macrophages/phagocytes

– engulf (eat) foreign invaders

◦ T cells - identify and destroy infected cells;

communicate with B cells

Humoral Immune response◦ B cells

– produce antibodies, immune memory

◦ Antibodies – specific proteins design to restrict spread of pathogen

When macrophage “eats” the bacteria it “displays” antigens

Helper T binds to antigens

Result: chemical message released◦ more Helper T made◦Killer T activated◦ Communicate with B cells

Antibodies ◦Bind to a surface antigen on bacteria and clumps them together so that macrophage can “eat them”

◦Complement proteins Put holes in bacterial cells

◦Can inactivate or destroy toxins

Antibodies bind to antigens

Chemical messages decrease B and T cells

IMMUNE MEMORY

◦Memory B cells are formed Future rapid response cells Circulate in blood

Memory T Cell

Suppressor T Cell

Memory B Cell

The next time that an individual encounters that same antigen, the immune system is ready to destroy it quickly.

MEMORY CELLS◦ Long term protection against re-infection for life

How?◦ Memory B cells remain in the blood. (Bone

marrow can remake as needed)◦ Recognize antigen (second time response)

Rapid and large production of specific antibodies

Short –term immunity◦ Some vaccines or fluids containing antibodies◦ Infants have antibodies from mother

Due to blood exchange during pregnancy Due to mother nursing child

Long-term immunity ◦ Stimulated by infection

◦ Can be obtained through vaccines made from infectious agents that are not infectious, but do cause antibodies to form

Long term immunity◦ Body has been exposed to infective agent

Disease or vaccine

Short term immunity◦ Individual given antibodies (but the body has not

learned how to make more)

Create a table with three columns and four rows

In the first column

Vaccine Antibiotic Antiviral

Column 1 – When are they used (before or during or after infection?)

Column 2 – What are they effective against?

Column 3 - Do they treat, prevent, or cure?

Column 4 Do you have other questions or comments to add?

Virus consumed by a macrophage

2. Macrophage displays the virus antigens

3. Helper T-Cell recognizes “enemy” . Call in the troops.

4. B cells and Killer T Cells are manufactured

5. B cells produce antibodies that bind the virus. Killer T Cells destroy infected body cells.

6. Suppressor T cells stop production of defense.

7. Memory cells remain for future rapid response.