Immune System

Question 1

Innate & Adaptive Immunity

Answer 1

Invertebrates have only innate immunity

Vertebrates have innate and adaptive immunity

Question 2

Innate defense

Answer 2

refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen’s appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood, and cells that attack foreign cells in the body.

Question 3

Adaptive (acquired) defense

Answer 3

refers to specific defense mechanisms that involve cells (lymphocytes) and proteins. Some of these cells have “memory”. This is the technical use of the term “immunity”.

Question 4

Innate defenses

Answer 4

first and second lines of defense
Found in all animals
-First Line includes both mechanical and chemical
-Skin with secretions of sebaceous (oil) glands
-Mucous membranes
-Ciliary escalator of respiratory system
-HCl of stomach
Second Line includes both cells, proteins, and “processes”
-Cells = macrophages and natural killer (NK) cells
-Proteins = complement and interferon
-Processes = fever and inflammation

Question 5

Macrophages

Answer 5

2nd line of defense
“big eaters”
Digest foreign substances (toxins and microbes) in a non-specific way
Represent the primary antigen presenting cells (APC’s)
• present foreign substances to lymphocytes of 3rd line
of defense (…..more later)

Question 6

NK Cells

Answer 6

Second line of defense
technically, these are a type of lymphocyte
- Primarily involved with killing cancer cells

Question 7

Complement proteins

Answer 7

“complement” both the non-specific as well as the “specific” -
The complement system consists of a number of small proteins in the blood, in general synthesized by the liver, and normally circulating as inactive precursors.
When stimulated by one of several triggers, proteases in the system cleave specific complement proteins and initiate an amplifying cascade of further cleavages.
The end-result of this activation cascade is massive amplification of the response and activation of the cell-killing membrane attack complex

Question 8

Interferons

Answer 8

Second line of defense
proteins produced by virus-infected cells
Interferons help other cells resist viruses
Inhibit viral replication
Found only in vertebrates

Question 9

The inflammatory response can

Answer 9

Disinfect tissues
Dilute toxins
Limit further infection (trap microbes)
Recruits phagocytes
Promotes healing

Question 10

Four Cardinal Signs of Inflammation

Answer 10

Swelling
Redness
Heat
Pain

Question 11

Tissue damage

Answer 11

triggers the inflammatory response
Damaged cells release histamine
Histamine leads to vasodilation
Dilated vessels become more leaky (increased vascular permeability)
Various WBC’s migrate out into tissue

Question 12

FEVER

Answer 12

• is defined as having a temperature above the normal range due to an increase in the body’s temperature set-point.
  
  • interleukin-1(IL-1) from macrophages targets the hypothalamus in the brain and re-sets the set-point and acts as a pyrogen

Question 13

The lymphatic system

Answer 13

is a network of
-Lymphatic vessels 
-Organs
Lymphatic vessels
-Collect fluid from body tissues
-Return it as lymph to the blood
Lymph organs
-Such as the spleen and lymph nodes
-Are packed with white blood cells that fight infections

Question 14

As lymph circulates through lymphatic organs it

Answer 14

Collects
-Microbes
-Microbe toxins
Transports them to lymphatic organs
-Macrophages in lymphatic organs engulf the invaders
-Lymphocytes mount acquired immune response

Question 15

Our immune system

Answer 15

Responds to foreign molecules called antigens
The acquired immune system 
-Reacts (adapts) to antigens
-…….And “remembers” an invader.
-The immune system has “memory”.

Question 16

Active & Passive Immunity

Answer 16

Infection or vaccination triggers active immunity
We can temporarily acquire passive immunity by receiving pre-made antibodies
Immunity can also be natural or artificial

Question 17

Two kinds of lymphocytes carry carry out the immune response

Answer 17

B cells
-Secrete antibodies
-Mount the humoral immune response
-Best against bacteria
T cells   
-Attack cells infected with viruses
-Cell-mediated immune response

Question 18

Millions of kinds of B cells and T cells

Answer 18

Each with different membrane receptors
Wait in the lymphatic system
Where they may respond to invaders

Question 19

Antigens

Answer 19

Not usually part of the host
Most are proteins or large polysaccharides on the surfaces of
-Viruses
-Foreign cells

Question 20

Antigenic determinants

Answer 20

Specific regions on an antigen

To which antibodies bind

Question 21

When an antigen enters the body

Answer 21

It activates only a small subset of lymphocytes
-Those with complementary receptors
The selected lymphocyte cells multiply into clones of short-lived effector cells
-Specialized for defending against the antigen that triggered the response
-And into memory cells that confer long-term immunity

Question 22

he steps of clonal selection

Answer 22

Primary immune response, clonal selection
-Occurs upon first exposure to an antigen
-Is slower than the secondary immune response
-Produces effector cells…..and……
-Memory cells that may confer lifelong immunity
Secondary immune response
-Memory cells are activated by a second exposure to the same antigen
-This initiates a faster and stronger response

Question 23

Antibodies

Answer 23

Are secreted by plasma (effector) B cells
Into the blood and lymph
An antibody molecule 
-Is Y-shaped
-With two antigen-binding sites 
-Specific to the antigenic determinants
-That elicited its secretion

Question 24

Antibodies promote antigen elimination through several mechanisms

Answer 24

Mark invaders ……neutralization
agglutination
precipitation
Which triggers mechanisms to neutralize or destroy invaders…….opsinozation (enhanced phagocytosis)

Activate complement system…..fix complement

Question 25

T-Cells

Answer 25

Regulatory
- Helper T cells………….up-regulate
- Suppressor T-cells…..down-regulate
Effector
- Cytotoxic T cells (aka “killer T-Cells”)
- Are primarily responsible for the cell-mediated immune response

Question 26

In the cell-mediated immune response, an antigen-presenting cell (APC) displays

Answer 26

A foreign antigen (a nonself molecule) and
One of the body’s own self proteins
To a helper T cell

Question 27

Major Histocompatability Complex

Answer 27

“Self Antigens” = MHC antigens
MHC Antigens = 
	Major Histocompatability Complex
MHC I = on all of the cells of the body
MHC II= only on APC’s

Question 28

The helper T cell

Answer 28

The helper T cell’s receptors 
-Recognize the self–nonself complexes
-The interaction activates the helper T cells
The helper T cell can then activate
-Cytotoxic T cells and
B cells

Question 29

Cytokines

Answer 29

Cytokines = cellular hormones = Biochemical Mediators of the Immune Response

- Interleukin-1…….from macrophages
	- activates Th-Cells
	- also acts as a pyrogen
- Interleukin-2…….from Th-Cell
	- activates B-cells and Tc-Cells
	- activates other Th-Cellsand re-activates itself

Question 30

Cytotoxic T cells

Answer 30

Cytotoxic T cells
-Are the only T cells that kill infected cells
Cytotoxic T cells
-Bind to infected body cells
-Destroys them
-Inserts perforin proteins into membrane

Question 31

The immune system normally reacts

Answer 31

Only against nonself substances

Not against self

Question 32

Transplanted organs

Answer 32

May be rejected
Because the transplanted cells lack the unique “fingerprint” of the patient’s self proteins
Donors are used that most closely match the patients tissues
Transplants between identical twins do not typically have this problem

Question 33

In autoimmune diseases

Answer 33

The immune system turns against the body’s own molecules
Examples include
-Lupus
-Rheumatoid arthritis
-Insulin-dependent diabetes mellitus
-Multiple sclerosis