1. Defense Against Infectious Disease
4/3/2019 5:35 PM
Defense Against Infectious Disease
6.3
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2. Preventing Pathogens From Entering Our Bodies
Pathogen – any living organism or virus that is capable of causing a disease
Pathogens include:
Virus
Bacteria
Protozoa
Fungi
Worms

3. Defense Against Infection
Nonspecific Infection (Prevention)
Primary Defense
Skin – widespread physical barrier
Two primary layers:
Dermis – Alive (on the bottom)
Contains: sweat glands, capillaries, sensory receptors, and dermal cells that give structure and strength to skin
Epidermis – mostly dead (on top)
Dermal cells die and are moved up
This dead layer is a good barrier against most pathogens (can’t infect a dead cell??)

4. Defense Against Infection
Nonspecific Infection
1st Line of Defense
Skin
As long as skin stays intact you are protected from pathogens entering living tissues
This is why it is important to cleans and cover cuts and abrasions

5. Defense Against Infection
Nonspecific Infection
1st Line of Defense
Stomach Acid
Stomach secretions destroy many swallowed pathogens
Acidic environment of the stomach helps to kill most ingested pathogens

6. Defense Against Infection
1st Line of Defense
Mucus
Saliva, mucus, and tears protect openings such as mouth, nose, and eyes
Cells of mucus membrane secrete mucus
Sticky substance that can trap pathogens
This prevents pathogens from reaching cells they could infect
Lysozyme - an enzyme contained in saliva mucus
and tears
Break down bacterial cell walls
Cilia hair like structures that helps capture pathogens

7. Defense Against Infection
Area with a mucous membrane
What it is and does?
Trachea
The tube that carries air to and from the lungs
Nasal Passages
Tubes that allow air to enter the nose and then the trachea
Urethra
A tube that carries urine from the bladder to the outside
Vagina
The reproductive tract leading from the uterus to the outside

8. Blood Clotting
Plasma proteins – have many purposes including blood clotting
Cuts in the skin are sealed by blood clotting
Two clotting proteins are:
Prothrombin
Fibrinogen
Present in blood plasma
Remain inactive till there is bleeding
Also platelets (cell fragments)
Form in bone marrow
They are large cells that break up to become platelets
Short life span 8-10 days

9. Blood Clotting Broken blood vessels:
Damage cells release chemicals that stimulate platelets to adhere to the damaged area
Damaged tissue and platelets release chemicals called clotting factors that convert prothrombin into thrombin
Thrombin is an active enzyme that catalyzes the conversion of soluble fibrinogen into relatively insoluble fibrin
Fibrin is a fibrous protein forms a mesh like network that helps stabilize the platelet plug
More and more cellular debris becomes trapped in the mesh and a clot is formed.

10. Blood Clotting

11. Blood Clotting
Blood clot formation in coronary arteries can cause blockage in these arteries that can lead to a heart attack

12. Defense Against Infection
Immune Response
A series of events when a pathogen enters the body
Primary Immune Response – the first encounter with a pathogen
Takes about a week to be successful which means you will experience symptoms of the disease
Secondary Immune Response – 2nd or 3rd encounter with a pathogen
Response is quicker and more intense, symptoms rarely experienced
Secondary immune response to an antigen is what we know as being immune to a disease.

13. Defense Against Infection
Antigens – any foreign substance that can
stimulate an immune response
Caused by proteins located on the outer surface of bacteria, viruses, or parasites

14. Defense Against Infection
Leucocytes (AKA white blood cells) - Cells in our bloodstream that help fight off pathogens
Also provide immunity for pathogens we encounter the second time

15. Defense Against Infection
2nd Line of Defense
Macrophages - Large white blood cells (leucocyte)
that are able to change their cellular shape to surround an invader
Because they can change shape it is not unusual for a macrophage to encounter an invader outside the blood stream
It is involved very early on in the immune process
Remember this AKA

16. Defense Against Infection
When a macrophage meets a cell it recognize whether that cell is part of the body or not.
“Self” vs “not-self”
Phagocytes typically contain many lysosomes in order to digest chemically whatever it engulfs
This is nonspecific response because the specific pathogen has not been recognized only that it is “not-self “

17. Specific Defenses: The Immune Response
Responds to particular pathogens
Recognizing “Self”
A healthy immune system recognizes all cells and proteins that belong in the body; as self
Recognizing “Not-self”
The immune system recognizes foreign organisms and molecules as other or “not-self”.
Once recognized as “not-self” it uses cellular and chemical weapons to attack them
Recognition is based on the protein molecules that make up part of the surface of all cells and viruses
This is a “nonspecific” response because the ID of the pathogen has not been established just “not-self”

18. Specific Defenses: The Immune Response
The immune system response to antigens by:
Increase the number of cells that attack the invader directly
Lymphocytes produce antibodies
Antibodies are protein molecules that are produced by the body in response to a specific type of pathogen.
Each pathogen is made up of either cells with cell membranes or viruses which have a protein coat call a capsid.
The proteins are called antigens!
Remember cell membranes have proteins

19. Specific Defenses: The Immune Response
An antibody is a protein
Each antibody is different and specific for each antigen
Still very similar in structure
Each antibody is a Y shaped protein
Binding Site
Where antibody attaches itself to an antigen
Proteins

20. Specific Defenses: The Immune Response
The leucocytes that produce antibodies are a type of cell called plasma cells
We all have many different types of antibody-producing plasma cells
Each type of plasma cell can produce one type of antibodies
Each plasma cell produces a small number of antibodies when compared to the infection
Our evolving immune system has a way of producing the same type of plasma cells when needed

21. Specific Defenses: The Immune Response
Typical primary immune response:
A specific antigen type is identified (virus)
A specific plasma cell is identified that can produce an antibody that will bind to the antigen (capsid on virus)
The specific plasma cell types clones itself (mitosis) to increase # rapidly
The newly formed “army” of specific plasma cells produce antibodies
Antibodies circulate throughout the body and find antigen
Using various mechanisms the antibodies help eliminate the pathogen
Some of the cloned antibody-producing plasma cells remain in the blood stream & provide immunity against a second infection (Memory Cells)
Memory plasma cells of this type respond quickly if the same antigen is encountered again (second immune response)

22. Human Immunodeficiency Virus
AIDS – Acquired Immunodeficiency Syndrome
HIV – (human immunodeficiency virus) the cause of AIDS
Attacks key cells within the immune system
Reduces the number of active lymphocytes
A loss in the ability to produce antibodies
Takes many years after infection before a person lose specific immune response
capability.
Results in AIDS

23. Human Immunodeficiency Virus
AIDS
Infected person can no longer fight off pathogens
Secondary infection often takes the life of a person
Opportunistic Disease – A disease that attacks a
person with weakened
immune system.

24. Human Immunodeficiency Virus
Only no-risk behavior with HIV transmission is abstinence from sexual activity and IV drug use
No cure but a new variety of drugs makes it possible to survive

25. Human Immunodeficiency Virus
Transmission – only through infected blood,
semen, vaginal secretions, or
breast milk
Four Main ways HIV is transmitted:
Sexual intercourse
Sharing needles
Contact with infected blood products
From infected mother to her child during pregnancy, birth, or breast feeding

26. Antibiotics
Chemicals produced by other microorganisms, to kill or control the growth of other organsims
Antibiotics work because:
Bacteria are prokaryotic
Body cells are Eukaryotic
There are differences in biochemical reaction and pathways
Antibiotics take advantage of these difference

27. Antibiotics There are different types of bacteria:
One might stop protein synthesis in bacteria
Still have no effect in normal cells ability to synthesis bacteria (Affect metabolic pathways)
One type may inhibit the production of a new cell wall by bacteria
Cell cannot grow and divide
Because viruses have no metabolism they have no effect on viruses

28. Antibiotics
Remember that one antibiotic blocks a selective aspect of a prokaryotic cells biochemistry that is different from eukaryotes
Bacteria show genetic variation just like everything else
Bacteria are massive in numbers and reproduce very quickly the mathematical odds that a genetic variant exists that is not affected by a antibiotic
Thus in a short time surviving bacteria can reproduce rapidly

29. Antibiotics
Long term use of antibiotics and overuse has led to many bacteria that are resistant to nearly all antibiotics (Pathogenic) in existence today
Some are resistant to multiple antibiotics.
Staphylococcus aureus (Staph) can be pathogenic
MRSA are strains of staph that are pathogenic
Difficult to treat and becoming more common

30. Antibiotics
Penicillin was developed as an antibiotic by Florey and Chain in the late 1930”s
Tested on mice infected with pneumonia
4 of the treated mice survived
4 of the untreated mice died
With only a small amount of penicillin they tested on a man that was close to death
He began to recover but the penicillin ran out
5 patients were then tested, all cured

31. Antibiotics
Florey and Chain’s research would not be regarded as safe today
Now extensive animal research is done to check for harmful effects
After this small and then larger doses are tested on healthy informed humans to see if the drug is tolerated
Only then is the drug tested on patient's with the disease
After large scale double – blind trails are carried out on patients to check effectiveness and rare side effects