chapter 43: the immune system

Question 1

What are pathogens?

Answer 1

agents that cause disease, infect a wide range of animals including humans

Question 2

What is the main function of the immune system?

Answer 2

recognizes foreign bodies and responds with the production of immune cells and proteins

Question 3

What is innate immunity?

Answer 3

a defense active immediately upon infections

Question 4

What is adaptive immunity?

Answer 4

involves specific recognition
acquired immunity develops after exposure to agents such as microbes, toxins and foreign substances

Question 5

What is the innate immunity in invertebrates?

Answer 5

1. exoskeleton is made of chitin and is first barrier to pathogens
2. digestive system is protected by chitin-based barrier and lysozyme
3. hemocytes carry out phagocytosis

Question 6

What is phagocytosis?

Answer 6

the ingestion and digestion of foreign substances including bacteria

Question 7

What are the innate defenses in vertebrates?

Answer 7

1. barrier defesnses
2. phagocytosis
3. antimicorbial peptides
4. natural killer cells
5. interferons
6. inflammatory response

Question 8

What is the mechanism of barrier defenses?

Answer 8

includes skin and mucous membranes of respiratory, urinary and reproductive tracts

Question 9

What is the cellular innate defenses mechanism?

Answer 9

• phagocytic cells recognize groups of pathogens by TLRs, Toll-like receptors.
• TLRs recognize fragments of molecules characteristics of a set of pathogens
• white blood cells engulf invading pathogens, creating vacuole

Question 10

What are the four main types of phagocytic cells?

Answer 10

1. neutrophils: engulf and destroy pathogens
2. macorphages: found throughout body
3. dendritic cells: stimulate development of adaptive immunity
4. eosinophils: release destructive enzymes

Question 11

What is the function of natural killer cells?

Answer 11

they circulate through the body and detect abnormal cells. they then release chemicals leading to cell death, inhibiting the spread of virally infected or cancerous cells

Question 12

What is the role of interferon?

Answer 12

provides innate defense, interfering with viruses and helping activate macrophages

Question 13

What is the inflammatory response?

Answer 13

1. is brought about molecules released upon injury or infection
   - mast cells release histamine, triggering blood vessels to dilate and become permeable
2. macrophages release cytokines, inhancing immune response. blood flows to site helps deliver antimicrobial peptides, accumulating pus.

Question 14

What is the use of a fever?

Answer 14

systematic inflammatory response triggered by substances released by macrophages in response to pathogens

Question 15

What are the two different types of lymphocytes?

Answer 15

1, T cells: lymphocytes mature in thymus
2. B cells: lymphocytes mature in bone marrow

Question 16

What are antigens?

Answer 16

substances that can elicit a response from B cell or T cell

Question 17

How do T and B cells bind antigen?

Answer 17

Via antigen receptors
small acessible part of an antigen that binds to antigen receptor called epitope

Question 18

What does antigen recognition by B cells cause

Answer 18

gives rise to cells that secrete a soluble form of the receptor called antibody or immunoglobulin

Question 19

How does antigen recognition by T cells work?

Answer 19

1. t cell binds to antigen fragments
2. antigen fragments are bound to cell-surface proteins called MHC molecules they are host proteins
3. MHC molecules bind and transport antigen fragments to cell surface (antigen presentation)

Question 21

what is the mechanism of proliferation for B cells and T cells?

Answer 21

1. once activated B/T undergoes multiple cell divisions (clonal selection) to produce a clone of identical cells
2. binding of a mature lymphocyte to an antigen initiates events that activate lymphocyte

Question 22

What are the two types of clones produced?

Answer 22

1. short-lived activated effector cells that act immediately.
2. long lived memory cells that can give rise to effector cells if the same antigen is encountered again

Question 23

What is immunological memory?

Answer 23

is responsible for long-term protections against diseases due to a prior infection or vaccination

Question 24

What happens after first exposure to specific antigen?

Answer 24

• primary immune response
  selected B and T cells give rise to their effector forms
• in secondary response, memory cells facilitate a faster, more efficient response

Question 25

What is the humoral immune response?

Answer 25

antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph

Question 26

What is cell-mediated immune response

Answer 26

specialized T cells destroy affected host

Question 27

How do helper T cells respond to antigens?

Answer 27

1. class II MHC molecules are the basis upon which antigen-presenting cells are recognized 2. antigen receptors on surface of helper T cells bind to the antigen and the class II MHC molecule (signals exchange between the two cells) 3. the helper T cells is activated, proliferates and forms clone of helper t cells

Question 28

How are the B cells activated?

Answer 28

1. in response to cytokines, a B cell proliferates and differentiates into memory B cells and plasma cells 2. activated B cells give rise to thousands of plasma cells 3. they produce and secrete antibodies 4. antigens recognized by B cells contain multiple epitopes

Question 29

What are the different functions of antibodies?

Answer 29

1. they mark pathogens for destruction 2. neutralization: they bind viral surface proteins preventing infection 3. opsonization: they bind to antigens on bacteria, triggering phagocytosis 4. antigen-antibody complex can bind to complement protein, triggering cascade of complement protein activation

Question 30

What are cytotoxic T cells?

Answer 30

- effector cells in the cell-mediated immune response - they kill cells infected by viruses or other intracellular pathogens - they secrete proteins that disrupt the membranes of target cells and triggers apoptosis

Question 31

What is immunization?

Answer 31

use of antigens artificially introduced into the body to generate an adaptive immune response and memory cell formation

Question 32

What is active immunity?

Answer 32

develops naturally when a pathogen invades the body and elicits a primary or secondary immune response

Question 33

What is passive immunity?

Answer 33

provides immediate, short-term protection

Question 34

What are allergies?

Answer 34

exaggerated responses to antigens called allergens

Question 35

What is not part of the insect immunity?

Answer 35

activation of natural killer cells

Question 36

An epitope associates with which part of an antigen receptor or antibody?

Answer 36

variable regions of a heavy chain and light chain combined

Question 37

Can a lymphocyte have receptors or multiple different antigens?

Answer 37

no

Question 38

What does vaccination increase?

Answer 38

lymphocytes with receptors that can bind to the pathogen

Question 39

What does not help a virus avoid triggering an adaptive immune response?

Answer 39

producing proteins very similar to those of other viruses