Chapter 21

Defense mechanism. Allows body to determine what is self or non-self.

Main function of the immune system

1. Agent: pathogen

2. Reservoir: place for germs to live

3. Portal of exit: a way out

4. Mode of transmission: method of transport

5. Portal of entry: way to enter new host

6. Susceptible host: for invasion

Components required for transmission from person to person to happen: [6]

Agent

Cells that body identifies as non-self. Things that can invade us and make us sick.

Pathogen (bacteria, viruses, fungi, cancer, donor cells)

Disease/injury-causing organisms and cancer cells [5 examples]

Bacterial flora

Bacteria that lives in body at all times. Protected by pH balance and skin.

1. Food

2. bodily fluids

3. animals

4. soil

5. water

Examples of common resevoirs for pathogens: [5]

1. Urine

2. blood

3. Sputum

4. Feces

Examples of common portals of exit for pathogens: [4]

Contact transmission

Method of transmission where germs are picked up off a surface. Transfers touch from skin/surface to skin.

Droplet transmission

Method of transmission where pathogens travel in the air from the reservoir up to 6 feet. Microscopic droplets transmitted by coughing, sneezing.

Airborne transmission

Method of transmission where pathogens travel and transfer in air for a longer distance and a longer time. Pathogens floating in the air around the person that has it all the time

Vector transmission

If an insect picks up an infection from soil, can ingest it (or if bitten by insect) and pathogens can be transferred in barrier breakdown of skin

1. Breakdown/cut in skin

2. ingestion through mouth

3. Inhaling through nose and mouth

4. Exchange of bodily fluids

5. mucous membranes of the eyes

Examples of common portals of entry for pathogens: [5]

Children and

the elderly

(also those with weakened immunity.)

Who are the most susceptible populations to pathogen invasion? [3.

Innate defenses

Inborn defenses that are fast acting. Includes the first and second line of defense.

Adaptive defenses

Slower defenses that strengthen over time. Acquires tools and skills to mount a more effective defense. Includes third line of defense

Skin

Physical barrier than protects from invasion (innate defense, first line). Has to break the barrier to enter, or enter through eyes, nose, mouth, etc. (other opening)

1. SKin

2. Mucous membranes

First line of defenses:

1. Chemical barriers (secretions, sebum, and sweat)

2. Enzymes (saliva, respiratory tract, tears)

3. Mucin (respiratory/digestive tract)

4. Defensins (mucous membranes and skin

Protective chemicals that provide barriers within first line of defense [4]

Defensins

Antimicrobial properties in mucous membranes and skin

Second line of defense

Once the barrier is broken, physiological function comes into play. White blood cells.

Toll-like receptors (TLRs)

Cells that play a central role in triggering immune response. Detects or recognizes invaders and sound the “alarm” that initiates the immune response.

Neutrophils

Most abundant white blood cells that die fighting. Tey become phagocytotic on exposure to infectious material.

Phagocytes

White blood cells that ingest and digest foreign invaders.

1. Phagocytes confront microorganisms that breach first line

2. Phagocytes must use receptors to bind to pathogen, trap the pathogen before it can be engulfed

3. Neutrophils and macrophages complete destruction by bringing it inside cell. Forms a capsule called a phagosome.

4. Phagosome binds with a lysosome, forming a phagolysosome to destroy bad pathogen

Steps of phagocytosis: [4]

Phagolysosome

Lysosome vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. Indigestible material is expelled via exocytosis.

Opsonization

If a phagosome is unable to destroy a pathogen (cannot bind and/or digest), what process is initiated?

Opsonization

Process where immune system uses antibodies or compliment proteins to coat the pathogen. Gives it “handles” that it can pull in. Covers it in compliment and antimicrobial properties.

Opsonin

Coats the pathogen and leads to enhanced taste and increased attraction during opsonization.

Natural killer cells

White blood cells that are always floating in blood. Can kill cancer and virus-infected cells before adaptive immune system is activated.

Induces apoptosis and can enhance inflammatory response.

How do natural killer cells take down pathogens? [2]

1. Pain

2. Heat

3. Redness

4. Swelling

5. loss of function

Cardinal signs of infection [5]

Uses inflammation as a way to protect and prevent further spread of the invasion, or further destruction by that microorganism or pathogen. Alerts the adaptive immune system and prepares for repair.

How does immune system use inflammation?

White blood cels in the immediate area send out chemicals recruiting more white blood cells. R

Release of chemicals will cause arteries and veins from bone marrow to site to become dilated and leaky.

Neutrophils cling to capillary wall

Will follow via diapedesis through holes in capillaries to area of drainage

How does inflammation happen/ is triggered? [4]

Diapedesis

The movement of white blood cells and other cells out of small arterioles, venules, and capillaries as part of the inflammatory response.

Work to enhance inborn defenses by attacking microorganisms and hindering ability to reproduce

Function of antimicrobial proteins

Interferons

Proteins produced by the body used to stop replication of viruses in the body. Produced by virally infected cells.

Complement

Group of proteins that provide mechanism for destroying pathogens that enter the body

1. Classical

2. MB-lectin pathway

3. Alternative pathway

Three pathways for complement:

Recruits the inflammatory system, recruits opsonization of pathogens. If it is undigestible immediately, will provide coating so that pathogen is digestible.

Function of complement:

Fever

Abnormally high body temperature, a systemic response to invading microorganisms

Pyrogens

Substance released by bacterium which produces fever when introduced or released in the blood

Pyrogens are produced by leukocytes and macrophages, and act on the hypothalamus, causing a rise in temperature.

How do pyrogens increase temp?

It can be good and help enhance the immune response (less than 38 degrees celsius)

Is a mild-low grade fever good?

It has an opposite effect. Starts to stop metabolic processes, and pathogens are able to move further into the body.

What happens when pyrogens stimulate a temperature above 38 degrees celsius?

Slowly, over time. Adapts and strengths with multiple exposures

How does the third line of defense stregnthen?

Adaptive “remembers”, creates a memory. Acquires tools and skills for a more mounted defense (unlike innate)

Key difference between adaptive and innate immunity:

The whole body: it is a systemic response. Innate is localized.

What part of the body is effected by adaptive defense? How is it different from innate?

1. active

2. Passive

Two types of humoral immunity:

1. Naturally acquired

2. Artificially acquired

Two types of active humoral immunity:

Naturally acquired active humoral immunity

Infection happens after coming into contact with pathogen. Pathogen gets through skin through second line, and comes into body. Humoral immune response that builds b cells that remember what happened:

Artificially acquired active humoral immunity:

Immune response that comes from vaccines. The artificial introduction of a pathogen to the system to amount an immune response.

Naturally acquired passive humoral immunity

Antibodies from mother to fetus in placenta or breast milk. Provides a infant that lacks a third line some extra support and protections

Artificially acquired passive humoral immunity

Injection of exogenous antibodies from the blood to be artificially injected into somebody else provides this immunity.

Antigens

Large signaling molecules that are not normally found in the body and their presence stimulates an immune response.

Lymphocytes have antibodies attached to cell membranes

Where are antibodies of lymphocytes attached?

Bone marrow

Where do B and T cells develop?

Bone marrow

Where do B cells mature?

Thymus

Where do T cells mature?

“naive” or “clean” b and t cells

B and T cells that have still matured but are new. Have not been exposed to pathogens or antigens yet.

They travel through secondary lymphoid organs, laying down B and T cells. Once exposed to a a bacterial antigen, picks up antibodies on outside of cell membrane and becomes bound to cells

Where do naive B and T cells go?

1. Become immune competent

2. Become self tolerant

Two important things that mature T and B cells are able to do:

Self tolerant

When a T or B cell is able to identify what is self

Immune cmpetent

When a T or B cell is able to identify what is not self

B cells floating in the blood.

B cell attaches to antigen, activates humoral response

Starts to clone itself

Some of the clones are effectors and some are fighters (produces extra antibodies)

Once effectors are done, drops antibodies and float in blood to serve as fighters later on

how does B cell become activated? [5]

1. Neutralization

2. Agglutination

3. precipitation

4. Complement

Four mechanisms by which antibodies provide defense:

Neutralization

Mechanism of defense that blocks specific sites on viruses or bacterial exotoxins so they cannot attach

Agglutination

Mechanism of defense when cells bind to the same antigen on more than one cell-bound antibody (ex: clumping of blood cells in transfusion reactions)

T cells activate, calling back second line.

If all else fails, what is the last immune response to activate?

They act like a “boss”

1. inflammation

2. Macrophages

3. activate other T cells

4. Regulate much of immune response

What do T cells activate in third line?

They become antigen presenting. They take a piece of what is left over and display MHC protein on outside of cell membrane.

What happens after a phagocyte gobbles and destroys a pathogen?

1. Class I MHC

2. Class II MHC

Two types of MHC complex:

All body cells except RBCs. healthy cells are ignored by these.

Cells that have type I MHC complex:

Displayed by antigen presenting cells

Cells that have type II MHC complex:

T cells attack cells that have love their initial fight and have been invaded by bacteria, viruses, fungi, or disease (cancer)

What do T cells attack?

Helper T cells

T cells that cannot kill but activate cells that do and lead the process

Cytotoxic T cells

T cells that actually do the damage

Autoimmune disorder

When body attacks its own cells. Ability to recognize self and non self is impaired.

Memory T cells

T cells that are able to remember for next time

Immunodeficiency

When the body is unable to/ not successfully mount a defense