Immunology

Question 1

Specificity

Answer 1

An immune response able to contain one microbial pathogen is rarely effective against a second microbe unless the two microbes are closely related. (I.e. Lock and key)

Question 2

Universality

Answer 2

The immune system can react to the whole universe of macromolecular foreign substances by mounting an immune response to the foreign substance. The immune system can attach virtually all microbes. (I.e. A hardware store that stocks keys to all locks)

Question 3

Three basic characteristics of immune responses

Answer 3

Specificity
Universality
Inducibility

Question 4

Adaptability

Answer 4

• immune response takes time to develop
• defenses they provide are usually not present at the time of first infection
• exposure to an antigen in the distant past can result in an ability to make faster and greater response on re-exposure to the same antigen

Question 5

Secondary response

Answer 5

Adaptability:

• exposure to an antigens the distant path can result in an ability to make faster and greater response on re-exposure to the same antigen.
• positive memory

Question 6

Negative memory

Answer 6

Adaptability

- pre exposure to an antigen can result in an lessened ability to respond to a subsequent challenge of the antigen

Question 7

Innate resistance

Answer 7

These mechanisms are present and very often effective at the time of infection and their characteristics change little following infection.

Question 8

Innate defense mechanisms are __________ whereas immune responses are __________

Answer 8

Constitutive

Inducible, a form of adaptability

Question 9

Three defensive systems in vertebrates

Answer 9

1) the surface of the body (particularly skin, presents a physical and chemical barrier to microbes finding their way into a body)
2) innate defenses by cells and molecules in blood that can provide protection should the first barrier fail
3) the immune system that comes into action should the two first levels of defense prove to be inadequate

Question 10

Innate defense have three characteristics that differ from those of the defense mechanisms constituting the immune system

Answer 10

1) they provide immediate protection upon infection
2) they are relatively non specific
3) they are constitutive or uninducible to a great degree

Question 11

4 main processes of innate defenses

Answer 11

1) inflammation
2) phagocytosis
3) processes initiated by complement
4) interferon production

Question 12

Inflammation

Answer 12

Inflammation is the overall process by which multiple forms of defense are brought to a site when skin, the first barrier of protection, is breached. Signals are given for blood cells and fluid to escape from the blood vessels in the vicinity of the injury. One molecule released at the site of injury is called histamine and is stored in mast cells. The local injection of histamine into skin causes local inflammation.

Question 13

Phagocytosis

Answer 13

• important in providing protection against bacteria
• the most important phagocytic cells in the blood are neutrophils and monocytes which are called macrophages when they leave the blood and enter the tissues.
• most important step is the binding of the bacterium to the surface of the phagocytic cell and the formation of a phagosome. Phagosome fuses with a lysosome to form a phagolysosome and these enzymes attack the bacterium often leading to “digestion”

Question 14

Processes initiated by complement

Answer 14

One protein component will often activate another down stream dormant component by causing the latters cleavage by proteolysis. One molecule of the up stream component can activate several molecules of the down stream component and thus amplify the signal.
- sometimes called the complement cascade

Question 15

The complement cascade can be initiated by two distinct mechanisms…

Answer 15

The classical- evolutionary more recent. Occurs as part of immune responses

The alternative pathway- evolutionary older. Involved in innate responses.

Question 16

Complement is involved in three distinct processes of innate resistance

Answer 16

1) compliment components are involved in inflammatory mediators
2) an activated component of the third component of complement, C3, called the C3b, binds to the surface of many bacteria and aids the process of phagocytosis by such cells as macrophages
3) binding if C3b to the surface of a bacterial cell leads to the formation of the membrane attach complex, that itself results in the formation of holes in membranes and subsequently lysis (death due to leaking) of the bacterium.

Question 17

Interferon (IFN) production

Answer 17

• important in defense against viral infections by its action of interfering with viral replication.
• three kinds a , b , g
• a and b interferon production occurs in cells infected by viruses
• lymphocytes infected by viruses produce a-IFN and fibroblasts produce b-IFN.

Question 18

Thycidides

Answer 18

• Greek historian
• first recorded observation implying that the immune system expresses memory
• also noted that only those who had recovered from the plague but not from other illnesses were protected. Therefore the memory is specific.

Question 19

Jenner

Answer 19

Protected individuals against small pox by inoculating them with material obtained from the lesions of cows suffering from cowpox.
- later this was termed vaccination by Pasteur in honor of Jenner

Question 20

Attenuated organisms

Answer 20

Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent.

• used to vaccinate and this protect (i.e. Polio)
• known as immunization

Question 21

Passive transfer of immunity

Answer 21

• immunity to toxins can be developed by immunizing with a sub lethal dose of the toxin or with toxoid (a toxin that is treated so that it is no longer toxic).
• when blood is collected from an immune animal it clots and the free yellow liquid that separates (serum) would inactivate the toxin. Administering the serum to normal I immunized animals conferred immunity to the toxins.

Question 22

Antibodies vs antigens

Answer 22

Antibodies- protective molecule sin immune serum

Antigens- the molecules or substances to which antibodies specifically bind

Question 23

To Aggutinate bacteria

Answer 23

Cause them to clump together

Immune serum can aggutinate bacteria

Question 24

Immune serum added to a filtrate of bacterial cultures _________ with the filtrate due to….

Answer 24

Precipitates

Due to the bacteria producing soluble, filterable molecules, and the immune serum contains antibodies specific for these soluble antigens.

Question 25

The processes in which precipitate is formed

Answer 25

Precipitin Reaction

Question 26

Is the precipitin reaction specific or non specific. Why?

Answer 26

Very specific.

This reaction happens when the immune serum is mixed with its appropriate soluble antigen.

Antibodies raised against tetanus toxin will form a precipitate with this antigen, whereas they will not react with diphtheria toxin.

Question 27

What is the job of antibodies

Answer 27

To bind to antigen and call upon various mechanisms to attack the antigen to which they are bound.

Question 28

Three example of how antibodies render the mechanisms of innate resistance

Answer 28

1) activation of complement

2) enhancement of phagocytosis 3) triggering acute inflammation

Question 29

Activation of complement

Answer 29

An example of how antibodies render the mechanisms of innate response

Immune serum kills bacteria in vitro by causing their lysis. Lytic property of immune serum is lost when heated. Border showed that immune serum will still kill when COMPLEMENTED with non heated normal serum. Heated immune serum provides the heat resistant specific recognition molecules, the antibodies, and normal serum provides the heat-labile non specific complement required to obtain lysis.

Question 30

Enhancement of phagocytosis

Answer 30

An example of how antibodies render the mechanisms of innate response

Immune serum contains specific antibodies that specifically enhance phagocytosis by phagocytic cells, such as macrophages. These antibodies are called opsonins

Question 31

Triggering acute inflammation

Answer 31

An example of how antibodies render the mechanisms of innate response

Histamine is stored in the granules of mast cells. These cells bind certain kinds of antibodies called cytophilic antibody and when the cell bound antibodies interact with antigen a series of events leads to the discharge of the contents (degranulation) of the mast cells (including histamine) thereby leading to acute and local inflammation.