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Biology 2312 > Chapter 51 > Flashcards

Chapter 51 Flashcards

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1
Q

Historically, the response of vertebrates to microbial invasion was divided into (2)

A

specific and nonspecific forms of defense

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2
Q

Now, a vertebrate’s response to microbial invasion is composed of (2)

A

innate and adaptive immunity

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3
Q

What is the key to the function of the immune system?

A

ability to distinguish self from nonself cells

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4
Q

Adaptive immunity is characterized by

A

genetic rearrangements that generate a diverse set of molecules that can recognize virtually any invading pathogen

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5
Q

What is the largest organ of the body?

A

skin

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6
Q

What is the skin’s surface pH?

A

3 to 5, because of the oil and sweat glands

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7
Q

Why is the acidic nature of skin important?

A

it’s acidic enough to inhibit the growth of many pathogenic microorganisms

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8
Q

Sweat contains the enzyme

A

lysozyme, which digests bacterial cell walls

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9
Q

What do epithelial cells produce as a defense?

A

produce a variety of small anti-microbial peptides

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10
Q

The skin is also home to (3)

A

normal flora; nonpathogenic bacteria; fungi

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11
Q

What happens to pathogenic bacteria that attempts to colonize the skin?

A

they are generally unable to compete with normal flora

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12
Q

The epidermis of the skin is how many cells thick?

A

10 to 30 cells thick

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13
Q

In addition to the skin, what are three other potential routes of pathogen entry?

A

digestive tract; respiratory tract; urogenital tracts

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14
Q

Each tract is lined by

A

epithelial cells, which are continuously replaced like in skin

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15
Q

What covers each epithelial surface?

A

a layer of mucus, secreted by cells scattered in between epithelial cells

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16
Q

What purpose does the mucus lining epithelial surfaces serve?

A

traps pathogens

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17
Q

What kills microbes present in food? (3)

A

saliva (which contains lysozyme); acidic stomach; digestive enzymes

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18
Q

How are microorganisms in inhaled air dealt with?

A

trapped by mucus in smaller bronchi/bronchioles before reaching warm/moist lungs (where they would likely flourish)

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19
Q

What happens to pathogens trapped by mucus in the bronchi/bronchioles?

A

mucus is swept up to the glottis by cilia from the epithelial cells and can be swallowed

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20
Q

What effect does smoking have on respiratory tract defenses?

A

nicotine paralyzes cilia of the respiratory system which results in unclean tracts

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21
Q

How does urine function as a pathogenic defense?

A

Acidic urine continually washes out pathogens from the urinary tract

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22
Q

What are four additional defense mechanisms that commonly occur in people?

A

vomiting, diarrhea, coughing, sneezing

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23
Q

Innate immunity involves (2)

A

soluble factors AND different types of blood cells

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24
Q

What is the characteristic portion of gram-negative bacteria that make it recognizable as part of innate immunity?

A

lipopolysaccharide found in gram-negative cell walls

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25
Q

What is the characteristic portion of all bacteria that make it recognizable as part of innate immunity?

A

peptidoglycan found in all bacterial cell walls

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26
Q

The receptors involved in innate immunity can be found

A

in solution (they’re soluble proteins) OR membrane proteins on the surface of blood cells

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27
Q

What is the best studied innate receptor protein?

A

Toll receptor in fruit flies

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28
Q

How many TLRs are there in humans? In mice?

A

11 TLRs in humans; 13 TLRs in mice

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29
Q

The TLRs found in humans and mice bind to

A

a variety of specific targets important to pathogen survival, which therefore do not vary greatly

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30
Q

Give six examples of targets of TLRs found in humans and mice.

A

gram-negative LPS, bacterial lipoproteins, bacterial peptidoglycan fragments, yeast cell-wall components, unmethylated CpG motifs in bacterial DNA, and viral RNA

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31
Q

How do TLRs accommodate a wide variety of shapes?

A

TLRs contain leucine-rich regions that fold to form binding pockets

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32
Q

What comprises the innate response to an infection? (3)

A

inflammatory response; production of antimicrobial peptides; production of cytokines which attract B/T/phagocytic cells

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33
Q

What was the next class of receptors to be discovered after Toll/TLR proteins?

A

cytoplasmic receptors

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34
Q

How do cytoplasmic receptors work?

A

bind to characteristic pathogen molecules and recognize invading pathogens in the cytoplasm of cells after phagocytosis

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35
Q

Cytoplasmic receptors are part of the response to

A

viral RNA

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36
Q

The response to viral RNA includes which receptor?

A

cytoplasmic receptors

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37
Q

What are soluble receptors?

A

receptors that circulate in serum; can respond to specific pathogen molecules

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38
Q

Give an example of a specific pathogen molecule recognized by soluble receptors.

A

lectin proteins

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39
Q

Lectin proteins bind to

A

mannose

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40
Q

Lectin proteins are important in

A

activating the complement system

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41
Q

Give an example of an antimicrobial peptide.

A

defensins

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42
Q

How do defensins work?

A

cysteines on defensins interact with positively charged AAs on pathogen surface; bind to outer membrane of gram-negative bacteria; can disrupt membrane and enhance phagocytosis

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43
Q

In addition to working against gram-negative bacteria, defensins can work effectively against

A

enveloped viruses

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44
Q

Defensins can induce what antimicrobial enzyme?

A

lysozyme

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45
Q

Gram-bacteria/enveloped viruses are targeted by

A

membrane attack complexes (MAC)

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46
Q

MACs come from

A

the complement cascade

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47
Q

Bacteria/fungi/enveloped viruses are targeted by

A

antimicrobial peptides

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48
Q

Antimicrobial peptides come from (2)

A

circulating phagocytes OR directly from epithelial cells

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49
Q

Bacteria/fungi are targeted by

A

circulating phagocytes

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50
Q

Circulating phagocytes come from (3)

A

cytokines; chemokines, complement cascade

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51
Q

Virus-infected cells are targeted by

A

natural killer (NK) cells

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52
Q

Natural killer cells come from

A

directly from virus-infected cells

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53
Q

What are the two types of interferons?

A

interferon type I and interferon type II

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54
Q

Type I interferons are synthesized when

A

a virus infects a cell

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55
Q

How do type I interferons act when a virus infects a cell?

A

act as messengers to protect normal, uninfected cells in the vicinity; induce degradation of RNA and block protein production in these cells; leads to cell death but stops spread of virus

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56
Q

Type II interferons are synthesized by (2)

A

T lymphocytes; natural killer cells

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57
Q

What is the name for type II interferons in humans?

A

IFN-gamma

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58
Q

IFN-gamma is secreted as part of

A

the immunological defense against infection and cancer

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59
Q

Cytokines are produced in response to signaling from

A

TLR receptors; internal receptors

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60
Q

Cytokines attract and cause (3)

A

attract nonspecific phagocytic cells; cause inflammation; signal to the adaptive immune system

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61
Q

What are the three basic defending leukocytes?

A

macrophages; neutrophils; natural killer cells

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62
Q

Phagocytic cells are associated with what type of immunity?

A

innate immunity

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63
Q

What are macrophages and what do they do?

A

large, irregularly-shaped cells that kill microorganisms by ingesting them through phagocytosis

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64
Q

Once a microorganism is inside the macrophage, what happens?

A

membrane-bound phagosome fuses with lysosome and lysozomal enzmes kill and digest the microoroganism

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65
Q

What other unusual molecule can be found within phagosomes?

A

oxygen-containing free radicals, which are reactive and degrade the pathogen

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66
Q

Oxygen-containing free radicals are found in what structure?

A

phagosomes in macrophages; neutrophils

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67
Q

(T/F) Macrophages exclusively digest bacteria.

A

False, they can digest viruses/debris/dust

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68
Q

Where are macrophages found in the body?

A

extracellular fluid that bathes tissues

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69
Q

What are monocytes?

A

undifferentiated macrophages found in the blood

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70
Q

In response to an infection, what do monocytes do? (2)

A

squeeze through endothelial cells and go to site of infection; there, they mature into active phagocytic macrophages

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71
Q

What is the most abundant circulating leukocyte?

A

neutrophils, which account for 50-70% of peripheral blood leukocytes

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72
Q

What is the first type of cell to appear at a site of damage/infection?

A

neutrophils

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73
Q

How do neutrophils digest pathogens?

A

also by phagocytosis similar to that of macrophages except that they produce even more oxygen radicals

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74
Q

In addition to oxygen radicals, what else do neutrophils produce as a defense?

A

defensin peptides

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75
Q

(T/F) Natural killer cells attack invading microbes.

A

False, they kill cells of the body that have been infected by a virus.

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76
Q

How do natural killer cells work?

A

kill cells of the body via apoptosis

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77
Q

On a molecular level, how do natural killer cells work? (3)

A

NK cells release perforins, which insert into the membrane and create pores; NK-produced granzymes enter pores and activate proteins that induce apoptosis; macrophages digest remaining cellular debris

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78
Q

NK cells attack tumor cells, often before

A

the tumor has a had a chance to divide sufficiently to be recognized as a tumor - this makes NK cells a very important defense against cancer

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79
Q

NK cells are said to play a role in

A

immune surveillance

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80
Q

(T/F) Inflammatory response involves only the immune system.

A

False, it involves several systems of the body.

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81
Q

The inflammatory response can be either ____ or ____

A

localized or systemic

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82
Q

What is an acute inflammatory response?

A

a response that starts rapidly but lasts for a short amount of time

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83
Q

What are some chemical alarm signals released by infected/injured cells? (3)

A

histamine; prostaglandins; bradykinin

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84
Q

Chemical alarm signals like histamine cause

A

vasodilation of local blood vessels, which increases flow of blood to site and causes the area to become red and warm; increase permeability of capillaries in area which causes edema; swelling puts pressure on nerves which causes pain

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85
Q

What is edema?

A

tissue swelling

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86
Q

The increased capillary permeability as part of the inflammatory response does what? (2)

A

initially promotes migration of phagocytic neutrophils from blood to extracellular fluid; neutrophils can digest pathogens

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87
Q

The pus associated with infections is a mixture of (3)

A

dead/dying pathogens; tissue cells; neutrophils

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88
Q

Neutrophils that are sent to an injury site as part of an inflammatory response do what? (2)

A

digest pathogens; signal other monocytes to enter and become macrophages to help digest

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89
Q

What is one manifestation of the acute inflammatory response?

A

fever

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90
Q

On a molecular level, what causes fever?

A

when a macrophage with a TLR on surface binds to pathogen, interleukin-1 is released and carried to brain, where it causes neurons in hypothalamus to raise body temp above 37 C

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91
Q

Why is an increased body temperature as a result of fever necessary?

A

promotes activity of phagocytic cells and impedes growth of microorganisms

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92
Q

Which cytokine is associated with fever?

A

interleukin-1

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93
Q

In addition to stimulating phagocytosis, how else does fever contribute to the body’s defense? (2)

A

causes spleen and liver to store iron; this reduces blood levels of Fe which bacteria need to grow

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94
Q

Why is a very high fever dangerous?

A

can denature critical enzymes

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95
Q

What is considered the max temperature limit?

A

40.6 C, anything above this can be fatal

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96
Q

During an acute inflammatory response, how does the liver aid in phagocytosis? (2)

A

liver releases acute-phase proteins at levels 1000x above serum concentration; these proteins bind to pathogens and promote their phagocytic ingestion

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97
Q

What are the two phagocytic cells associated with the inflammatory response?

A

neutrophils and macrophages

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98
Q

What is the complement system?

A

the chemical defense of a vertebrate body that consists of a battery of proteins that become activated by the walls of bacteria/fungi

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99
Q

Approximately how many different proteins are associated with the complement system, and where are they found?

A

30 different proteins that circulate freely blood plasma

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100
Q

How are complement proteins activated?

A

mannose-binding lectin protein OR reactions involving charged species on surface of pathogens

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101
Q

When the complement system is activated, what happens? (3)

A

complement proteins aggregate to form membrane attack complex (MAC) that inserts itself into the pathogen plasma membrane; MAC channels extracellular fluid into pathogen; pathogen swells and bursts

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102
Q

What is C3b?

A

a complement protein that coats the surface of invading pathogens

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103
Q

What does C3b do?

A

helps direct neutrophils and macrophages to the pathogen for digestion; useful for pathogens that don’t have a lipid membrane that MACs can attach to

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104
Q

Mast cells and basophils

A

release histamine and other mediators in response to stimulation by complement cells

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105
Q

An effective chicken pox vaccine was developed in

A

1991

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106
Q

Which virus causes chicken pox?

A

varicella zoster

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107
Q

The scientific study of immunity began with

A

Edward Jenner in 1796

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108
Q

Smallpox is caused by what virus?

A

variola virus

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109
Q

What is vaccination?

A

injecting a harmless agent to confer resistance to a dangerous one

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110
Q

Modern resistance to malaria/herpes involve delivering antigens associated with what virus?

A

vaccinia virus, which is related to the cowpox virus

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111
Q

What is an antigen?

A

molecule that provokes a specific immune response

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112
Q

Generally speaking, what are the most effective antigens?

A

large, complex proteins

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113
Q

What is the relationship between foreign-ness and immune response?

A

the more foreign an antigen is, the greater the immune response will be

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114
Q

What is another name for epitopes?

A

antigenic determinants

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115
Q

All cells in blood ultimately derive from

A

the division/differentiation of hematopoietic stem cells

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116
Q

What is hematopoiesis?

A

division/differentiation of hematopoietic stem cells to produce cells in blood

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117
Q

Where are hematopoietic stem cells originally found, and where do they migrate afterwards?

A

originally found in yolk sac; migrate to fetal liver/spleen and then to bone marrow

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118
Q

Hematopoietic stem cells give rise to what two types of cells?

A

lymphoid progenitors; myeloid progenitors

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119
Q

Lymphoid progenitors give rise to (3)

A

B lymphocytes; T lymphocytes; natural killer cells

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120
Q

B lymphocytes come from

A

lymphoid progenitors

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121
Q

T lymphocytes come from

A

lymphoid progenitors

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122
Q

Natural killer cells come from

A

lymphoid progenitors

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123
Q

Myeloid progenitors give rise to

A

erythrocytes; platelets; all other cells of the immune system

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124
Q

Which general blood cell is responsible for adaptive immunity?

A

lymphocytes

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125
Q

Monocytes give rise to

A

macrophages

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126
Q

Eosinophils are important in

A

the elimination of helminths (flatworms)

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127
Q

How do eosinophils eliminate helminths? (2)

A

secretion of digestive enzymes through perforin pores inserted into helminth plasma membrane; phagocytosis

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128
Q

In addition to the elimination of helminths, what else do eosinophils do?

A

play a role in exacerbating chronic inflammatory diseases like asthma or inflammatory bowel disease

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129
Q

(T/F) Basophils are phagocytic.

A

False, they are not phagocytic.

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130
Q

(T/F) Mast cells are not phagocytic.

A

True, they are not phagocytic.

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131
Q

Which cell is particularly important in the allergenic response?

A

mast cells

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132
Q

Dendritic cells are important in

A

the activation of T cells

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133
Q

Which cells form a link between innate and adaptive immunity?

A

dendritic cells

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134
Q

What is the function of helper T cells? (2)

A

recognizes foreign peptides on antigen-presenting cells; induces release of cytokines that activate B cells or macrophages

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135
Q

What is the function of cytotoxic T cells?

A

recognizes and kills “altered-self” cells like virally infected or tumor cells

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136
Q

What is the function of B cells? (3)

A

binds specific, soluble antigens with membrane-bound antibody; serves as antigen-presenting cell to helper T cells; when activated, it differentiates into plasma cells and memory B cells

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137
Q

What is the function of plasma cells? (2)

A

derived from activated B cells; is a biochemical factory devoted to secretion of antibodies against antigens

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138
Q

What is the function of natural killer cells?

A

rapidly recognizes, kills virally infected cells

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139
Q

What is the function of monocytes? (2)

A

precursor of macrophages; located in blood

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140
Q

What is the function of macrophages? (2)

A

phagocytic tissue cell that is a component of the body’s first cellular line of defense; serves as antigen-presenting cell to helper T cells

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141
Q

What is the function of neutrophils? (2)

A

phagocytic tissue cell that is a component of the body’s first cellular line of defense; found in blood in large numbers until attracted to sites of inflammation

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142
Q

Which cells serve as antigen-presenting cells to helper T cells? (3)

A

B cells; macrophages; dendritic cells

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143
Q

What is the function of eosinophils?

A

important in the elimination of parasites; involved in chronic inflammatory diseases

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144
Q

What is the function of basophils?

A

circulating cell that releases mediators like histamine, prostaglandins for inflammation

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145
Q

Where are mast cells located?

A

under mucosal surfaces

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146
Q

What is the function of mast cells? (2)

A

releases mediators like histamine, prostaglandins; triggered by inflammatory and allergenic responses

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147
Q

What is the function of dendritic cells?

A

antigen-presenting cells to naive helper T cells; helps activate naive cytotoxic T cells

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148
Q

The adaptive immune system is characterized by what four traits?

A

specificity of antigen recognition; wide diversity of antigens that can be recognized; memory, where the immune system responds faster to an antigen the second time; ability to distinguish self-antigens from nonself

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149
Q

What are lymphocytes?

A

type of white blood cell involved in immune response

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150
Q

What are the two principal classes of lymphocytes?

A

B cells and T cells

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151
Q

What kinds of proteins do lymphocytes have on their surfaces?

A

have receptor proteins on the surfaces that recognize epitopes

152
Q

Which system dominates in the early part of pathogen response, and which system dominates later?

A

innate system dominates first, and then adaptive system dominates

153
Q

Which cells bind antigens/have the receptors necessary to bind antigens?

A

B cells and T cells

154
Q

Describe B cell receptors. (2)

A

immunoglobulin (Ig) molecules with a Y-shaped structure; each B cell has a single Ig that binds to a single antigenic determinant

155
Q

Describe T cell receptors. (2)

A

simpler than Ig molecules; can only bind to antigens bound to another cell

156
Q

(T/F) Lymphocytes tend to have similar specificities.

A

False, they tend to be unique.

157
Q

What is a naive lymphocyte?

A

lymphocyte that hasn’t encountered an antigen before

158
Q

What is clonal selection?

A

amplification of a clone of an immune cell stimulated by antigen recognition

159
Q

What happens to the cells produced by clonal selection?

A

some respond to the antigen, others become memory cells

160
Q

What is humoral immunity?

A

part of adaptive immune system involving B cells that produce soluble antibodies specific for foreign antigens

161
Q

(T/F) T cells secrete antibodies.

A

False, T cells do NOT secrete antibodies

162
Q

What is cell-mediated immunity?

A

part of adaptive immune system mediated by T cells

163
Q

What are the two types of T cells?

A

cytotoxic T cells; helper T cells

164
Q

What are the two ways someone can acquire immunity?

A

infection/immunization; getting antibodies from another human (like a mother)

165
Q

What is active immunity?

A

activation of specific lymphocytes and generation of memory cells

166
Q

What is passive immunity?

A

obtainment of antibodies from another human (like your mother), without generating memory cells

167
Q

(T/F) Antibodies are immortal.

A

False, they degrade with time.

168
Q

T cells are produced in

A

the thymus

169
Q

What are the two sets of organs in the immune system?

A

primary lymphoid organs; secondary lymphoid organs

170
Q

What organs are part of the primary lymphoid organs? (2)

A

bone marrow; thymus

171
Q

What organs are party of the secondary lymphoid organs? (3)

A

lymph nodes; spleen; mucosa-associated lymphoid tissue (MALT)

172
Q

Where do B cells mature?

A

bone marrow

173
Q

What is the name for immature B cells?

A

progenitor B cells

174
Q

Which process gives rise to B cells?

A

hematopoiesis

175
Q

Where does DNA rearrangement of immunoglobulin genes occur?

A

in the bone marrow when B cells are maturing

176
Q

How many Ig molecules does a B cell contain on its surface?

A

10^5

177
Q

What happens to lymphocytes that bind to self-antigens?

A

are killed via apoptosis

178
Q

Where is MALT located?

A

small intestine

179
Q

Where do progenitor T cells get produced?

A

bone marrow

180
Q

Where do progenitor T cells go from the bone marrow?

A

thymus

181
Q

What receptor is located on T cells?

A

T-cell receptor (TCR)

182
Q

TCR is produced by

A

gene rearrangements as T cells mature in thymus

183
Q

How many TCRs can be found on one T cell?

A

10^5

184
Q

B cells recognize what kinds of epitopes?

A

epitope of an intact antigen that may or may not be a protein

185
Q

T cells recognize what kinds of epitopes?

A

only recognize the peptide fragment of a protein antigen, and peptide fragment must be bound to series of self-proteins

186
Q

What is the major histocompatability complex? (2)

A

set of protein cell-surface markers anchored in plasma membrane which helps immune system identify “self”; all cells of a given individual have the MHC protein

187
Q

What percent of B cells are ultimately released from the bone marrow?

A

10%

188
Q

What percent of T cells pass the two-step screening?

A

5%

189
Q

Under what conditions are T cells eliminated in the thymus during the selection process?

A

if the T cells’ TCRs bind to strongly or don’t bind at all to MHC proteins

190
Q

What explains swollen glands during an infection?

A

lymphocytes responding to antigens pass out of capillaries and back into lymph nodes

191
Q

The immune response to neisseria meningitidis occurs in

A

the spleen

192
Q

Which blood vessel carries blood to the spleen?

A

splenic artery

193
Q

What is the white pulp?

A

regions of the spleen immediately surrounding arterioles

194
Q

Where are antigens released in the spleen?

A

ground tissue

195
Q

How do antibodies and active lymphocytes exit the spleen?

A

splenic vein

196
Q

The mucosa-associated lymphoid tissue (MALT) includes (3)

A

tonsils; appendix; follicles located under mucosal surfaces

197
Q

The MALT follicles are composed of (2)

A

lymphocytes (mostly B cells but some T cells); macrophages

198
Q

How does the MALT tissue serve as a line of defense?

A

any antigens that pass through mucosa are stopped by lymphocytes in the follicles

199
Q

Adaptive immunity first arose in

A

cartilaginous fish

200
Q

Which immune organs do sharks and rays have? (3)

A

thymus; spleen; MALT

201
Q

Bone marrow with hematopoiesis first originated in

A

amphibians

202
Q

Lymph nodes first appeared in

A

birds

203
Q

Describe the second form of adaptive immunity found in jawless fish. (3)

A

don’t have B/T cells, but instead lymphocytes have receptor proteins with repeats of leucine; similar diversity; different structure

204
Q

Cytotoxic T cells have what protein on their surface?

A

CD8 protein (CD8+ cells)

205
Q

Helper T cells have what protein on their surface?

A

CD4 protein (CD4+ cells)

206
Q

CD8 proteins are found on

A

cytotoxic T cells

207
Q

CD4 proteins are found on

A

helper T cells

208
Q

How are CD4/CD8 cells activated?

A

these cells must recognize peptide fragments bound to MHC proteins

209
Q

How are CD4/CD8 cells distinguished? (2)

A

they recognize different classes of MHC proteins; they differ in roles after being activated

210
Q

What is the name for proteins encoded by the MHC complex in humans?

A

human leukocyte antigens (HLAs)

211
Q

The genes encoding MHC proteins are

A

highly polymorphic (in some cases, over 500 alleles), so HLAs are different for each individual, like a fingerprint

212
Q

What are the two classes of MHC proteins?

A

MHC class I proteins; MHC class II proteins

213
Q

Where are MHC class I proteins found?

A

present on every nucleated cell of the body

214
Q

Where are MHC class II proteins found?

A

found only on antigen-presenting cells (macrophages, B cells, dendritic cells)

215
Q

Cytotoxic T cells respond to which class of MHC proteins?

A

cytotoxic T cells respond to peptides bound to MHC class I proteins

216
Q

Helper T cells respond to which class of MHC proteins?

A

Helper T cells respond to peptides bound to MHC class II proteins

217
Q

(T/F) B cells recognize MHC proteins.

A

False, they don’t recognize MHC proteins - only Tc and Th cells do.

218
Q

Where are T cells normally activated, and why?

A

normally activated outside of primary lymphoid organs (in secondary lymphoid organs) so that they don’t target self cells, and instead target foreign antigens

219
Q

The TCRs of Tc cells recognize

A

peptides of endogenous antigens bound to MHC class I proteins

220
Q

What are endogenous antigens?

A

self-protein or viral protein produced by an infected cell – produced by self cells

221
Q

Which cell in particular presents antigens that activate Tc cells?

A

dendritic cells

222
Q

What is cross-presentation?

A

process in dendritic cells in which virus/tumor cells are ingested and then viral/tumor peptides are placed on MHC Class I proteins

223
Q

What happens when a Tc cell binds to a dendritic cell undergoing cross-presentation? (4)

A

binding to dendritic cells occurs at CD8 site; activated Tc cells are generated; memory Tc cells are generated; activated Tc cells circulate through body to bind to similar dendritic cells with the same foreign peptide

224
Q

How do Tc cells induce apoptosis? (3)

A

Tc cell secretes perforin monomers to create pores in target membrane; granzymes enter and activate caspases; caspases cause apoptosis

225
Q

What do Th cells secrete?

A

low-MW proteins called cytokines

226
Q

What is the purpose of cytokines in the context of Th cells?

A

they initiate signaling cascades in immune system cells that promote activation or differentiation

227
Q

(T/F) Cytokines promote activation/differentiation of immune system cells only.

A

False, they can initiate cascades in other cells, too.

228
Q

Cytokines are secreted at what concentration?

A

cytokines are secreted at low concentrations because they are very potent and so that they only bind to nearby cells

229
Q

What is an exception to the norm that cytokines only bind to nearby cells?

A

IL-1, which travels to the hypothalamus to induce fever

230
Q

What is another name for humoral immunity?

A

antibody-mediated immunity

231
Q

What are the two types of immune responses?

A

humoral or cell-mediated

232
Q

How do B cells acquire foreign antigens?

A

receptor-mediated endocytosis

233
Q

How are foreign antigens made presentable to Th cells? (4)

A

once inside macrophages/dendritic cells/B cells, they are degraded in acidic endosomes or lysozymes; bind to MHC class II peptides and are displayed on surface; Th cells recognize and bind to this complex

234
Q

The CD4 protein of Th cells bind to what part of MHC class II proteins?

A

CD4 protein binds to conserved regions of MHC class II protein

235
Q

Naive Th cells express

A

a protein called CD28

236
Q

What must CD28 do?

A

must bind to protein B7 if the T cell is to be activated

237
Q

Where is B7 found? (2)

A

only on antigen-presenting cells; highest levels on dendritic cells

238
Q

Why is B7 important?

A

form of regulation necessary due to the potency of cytokines

239
Q

Activated Th cells give rise to

A

both effector Th and memory Th cells, just like Tc cells

240
Q

Which cells mediate transplant rejection?

A

T cells

241
Q

What happens when T cells encounter non-self MHC-peptide complexes on transplanted tissues?

A

TCRs on these T cells bind weakly to the MHC complex because the structure of the non-self MHC-peptide complex resembles the structure of a self MHC-foreign peptide complex

242
Q

What is cyclosporin?

A

drug that blocks activation of lymphocytes to suppress immune system rejection of a transplant

243
Q

(T/F) Cytokines are released exclusively by Th cells.

A

False, many other cells do, as well.

244
Q

What is IL-12? (2)

A

a cytokine released when PAMP molecules bind to TLRs; IL-12 binds to Th cells to increase their level of activation

245
Q

What does tumor necrosis factor-alpha do?

A

bind to blood vessels to induce local/systemic increase in vascular permeability

246
Q

Plasma B cells produce

A

soluble antibodies of the same specificity as the same antibodies produced by the parent B cell

247
Q

Draw the structure of an immunoglobulin molecule.

A

pg. 1070

248
Q

What region of the immunoglobulin is responsible for its specificity?

A

the specificity resides in the amino-terminal half of each Fab region

249
Q

What is the variable region of the immunoglobulin?

A

the amino-terminal half of the Fab region

250
Q

Which chains of the immunoglobulin have variable regions?

A

both the light chain and heavy chain have a variable region

251
Q

Which chains of the immunoglobulin have constant regions?

A

both the light chain and heavy chain have a constant region

252
Q

In mammals, the light-chain constant regions consist of (2)

A

a kappa sequence and a lambda sequence, which have equivalent functions

253
Q

In mammals, the heavy-chain constant regions consist of (5)

A

gamma, alpha, mu, epsilon, delta sequences (basis for IgG, IgA, IgM, IgE, IgD)

254
Q

Which characteristics of the immunoglobulin determine the specificity for antigen epitopes? (3)

A

size, shape, and AA sequence in the antigen-binding site

255
Q

How many epitopes can bind to an immunoglobulin?

A

2 epitopes

256
Q

The function of immunoglobulins depends on

A

its class

257
Q

The class of immunoglobulins depends on

A

the Fc portion of the heavy-chain constant region

258
Q

How does the Fc region help in the elimination of antigens? (2)

A

Most cells have Fc receptors, so when an antigen binds to an antibody, a phagocyte can bind to the Fc region and make it easier to eliminate the antigen; specific immunoglobulins can interactions between non-specific cells and antigens

259
Q

(T/F) Antibodies kill pathogens directly.

A

False, they target pathogens and let phagocytes destroy them.

260
Q

Describe the function of IgG. (3)

A

major antibody secreted during secondary response; neutralizes antigens by promoting phagocytosis; activates complement

261
Q

Describe the function of IgA. (2)

A

most abundant form of antibody in body secretions; high density of IgA-secreting cells in MALT

262
Q

Describe the function of IgM. (3)

A

first antibody to be secreted during primary immune response; promotes clumping and precipitation; activates complement

263
Q

Describe the function of IgE. (2)

A

Fc binds to mast cells + basophils; allergen binding to V regions promotes release of mediators which triggers allergic reaction

264
Q

Describe the function of IgD. (2)

A

present only on surfaces of B cells; serves as antigen receptor

265
Q

What is the shape of IgM? (2)

A

monomeric in the membrane of a B cell; secreted as a pentamer

266
Q

What is the shape of IgD?

A

monomer

267
Q

What is the shape of IgG?

A

monomer

268
Q

What is the shape of IgA?

A

dimer

269
Q

What is the shape of IgE?

A

monomer

270
Q

Which immunoglobulins are monomers? (3)

A

IgG, IgE, IgD

271
Q

Which immunoglobulins are found on mature, naive B cells?

A

IgM, IgD

272
Q

How are B cells activated by IgD?

A

B cells can be activated by the cross-linking of two IgD molecules

273
Q

Once a B cell is activated, what happens to IgD?

A

IgD is no longer displayed on the cell surface?

274
Q

Which immunoglobulin(s) are normally not secreted by B cells?

A

IgD

275
Q

Which immunoglobulin is the major antibody in blood plasma/tissues?

A

IgG - makes up 75% of plasma antibodies

276
Q

Which antibodies involved in providing passive immunity to a fetus?

A

IgG (through placenta), IgA (through breastmilk)

277
Q

Which immunoglobulin is the major antibody in external secretions?

A

IgA

278
Q

Which antibody has a low concentration in plasma?

A

IgE

279
Q

On secretion, most IgE becomes

A

bound to mast cells and basophils that recognize the Fc portion of IgE

280
Q

Which antibody provides a defense against helminth worms, and how?

A

IgE, through perforin pores

281
Q

How many different antigen binding sites can a human B cell generate?

A

10^10

282
Q

How is the variable region assembled, and why is this important?

A

assembled by joining 2-3 DNA segments together; provides genetic diversity needed to recognize many epitopes

283
Q

What is the name for the process that generates variable regions?

A

DNA rearrangement

284
Q

How is DNA rearrangement different from crossing over in meoisis? (2)

A

DNA rearrangement occurs between loci on the same chromosome; DNA rearrangement is site-specific

285
Q

When does DNA rearrangement occur?

A

as a progenitor B cell matures in the bone marrow

286
Q

What happens after DNA rearrangement occurs in the bone marrow?

A

mRNA is produced that can be translated as either a heavy or light chain

287
Q

What is allelic exclusion?

A

DNA rearrangement occurs for the heavy chain and light chain loci on only one homologue, which makes the B cells of only one specificity

288
Q

What are V/D/J segments?

A

50 V segments, 30 D segments, 6 J segments - clusters of DNA sequences found in human immunoglobulin heavy-chain gene loci

289
Q

(T/F) V segments are similar in size to each other.

A

True, they are equal in size, but have different nucleotide sequences - same goes for D/J segments

290
Q

What is the first DNA rearrangement in maturing B-cells? (2)

A

site-specific recombination event joining one of the D segments onto one of the J segments; intervening DNA is deleted/degraded

291
Q

V segments stand for

A

variable segments

292
Q

D segments stand for

A

diversity segments

293
Q

J segments stand for

A

joining segments

294
Q

An immunoglobulin (Ig) protein is encoded by

A

V/D/J segments + constant region

295
Q

What is the second DNA rearrangement in maturing B-cells?

A

combined DJ joins to V segment

296
Q

Light chains are encoded by

A

V/J segments + constant region

297
Q

What are the two types of constant regions in DNA rearrangement, and which region do they bind to?

A

a mu or sigma constant region, which binds to the variable region

298
Q

IgM has what kind of constant region?

A

mu constant region

299
Q

IgD has what kind of constant region?

A

sigma constant region

300
Q

How many different V/D/J combinations can be formed?

A

~9000

301
Q

What additional mechanisms allow for further DNA rearrangement beyond V/D/J segments?

A

nucleotides are added/deleted from each segment to shift reading frame; genes show elevated mutation rate

302
Q

What is somatic hyper-mutation?

A

genes that code for Ig proteins show elevated mutation rates to allow for more diversity (up to 10^10 possible variable regions)

303
Q

Draw the structure of a TCR.

A

draw pg. 1074

304
Q

How many chains does TCR have?

A

2

305
Q

Which region of TCR binds to an MHC-peptide complex?

A

amino-terminal domian – the variable region, distal to the membrane

306
Q

Which region of TCR is constant?

A

membrane-proximal domain – constant region

307
Q

(T/F) TCRs are secreted.

A

FALSE, TCRs are NOT secreted.

308
Q

Which is more effective, the primary response or secondary response to an antigen?

A

the secondary response is more effective

309
Q

Which is more rapidly activated, memory cells or naive lymphocytes?

A

memory cells

310
Q

The class of immunoglobulin produced is dictated by

A

the identity of the cytokines derived from activated Th memory cells that bind to the B cells in the 2ndary response

311
Q

What is immunological tolerance?

A

process where immune system learns to not react to self-antigens

312
Q

When does the process of immunological tolerance begin in humans?

A

fetal stage

313
Q

The failure of immunological tolerance leads to

A

autoimmune diseases

314
Q

Autoimmune diseases, generally, are caused by

A

the failure of immunological tolerance

315
Q

What happens when autoimmune diseases are produced? (3)

A

autoreactive T cells become activated; autoreactive B cells produce autoantibodies; extensive organ damage occurs

316
Q

How many known autoimmune diseases are there?

A

more than 40

317
Q

What percentage of the population is affected by autoimmune diseases?

A

5 to 7%; 2/3 of this are women

318
Q

What drugs are administered to suppress the immune system? (2)

A

corticosteriods; nonsteroidal anti-inflammatory drugs (such as aspirin)

319
Q

What is the most common form of allergy?

A

immediate hypersensitivity

320
Q

Immediate hypersensitivity is the result of

A

overproduction of IgE in response to allergens

321
Q

What is the most common allergy and where does it come from?

A

seasonal hay fever, provoked by pollen from ragweed

322
Q

What happens the first time someone encounters an allergen?

A

allergen binds to/activates B cells; activated Th cells releases IL-4 cytokine; IL-4 dictates production of IgE from B cell; IgE rapidly binds to mast cells/basophils; IgE secretes histamine/prostaglandins which produces symptoms of allergy

323
Q

What happens the second time someone encounters an allergen?

A

allergen binds to IgE which rapidly binds to mast cells/basophils; IgE secretes histamine/prostaglandins which produces symptoms of allergy

324
Q

What is systemic anaphylaxis? (3)

A

life-threatening because BP drops; epiglottis swells to block trachea; bronchial constriction prevents exit of air from lungs

325
Q

What is anaphylactic shock?

A

combination of blocked trachea; air blocked from leaving lungs; drop in BP

326
Q

What is local anaphylaxis? (3)

A

itchy welts/hives; mild asthma; diarrhea (mild reaction)

327
Q

What are some allergy treatments?

A

antihistamines; drugs that block activation of mast cells/basophils; hyposensitization

328
Q

Delayed type hypersensitivity is mediated by

A

Th cells and macrophages

329
Q

Delayed-type hypersensitivity symptoms occur

A

about 48 hours after a second exposure to the antigen

330
Q

Give an example of delayed-type hypersensitivity.

A

contact dermatitis

331
Q

A delayed-type hypersensitivity response requires

A

the antigen entering the body to travel to a secondary lymphoid organ (i.e. lymph nodes), where they activate Th cells; Th cells then travel around the body and release cytokines to activate macrophages

332
Q

What acts as the antigen on blood cell surfaces?

A

protein-sugar complex

333
Q

How do the antigens on blood cell surfaces differ?

A

differ with regard to the sugar present (or absent, in the case of O)

334
Q

Which class of antibodies recognize the monosaccharide differences in our red blood cells?

A

IgM antibodies produced in response to carbohydrates on bacteria living inside of us

335
Q

IgM, in the context of blood groups, can

A

recognize the monosaccharide differences in our red blood cells (only the IgM produced in response to bacterial carbohydrates)

336
Q

What is another important blood-borne antigen?

A

Rh factor

337
Q

The Rh protein is either

A

present (Rh positive) or absent (Rh negative)

338
Q

What happens if an Rh negative person receives a transfusion of Rh positive blood?

A

Rh negative person will produce antibodies to foreign Rh protein on transfused cells

339
Q

(T/F) Mother and fetus can have different Rh statuses.

A

True

340
Q

Mother (Rh negative) and fetus (Rh positive) having different Rh statuses results in

A

hemolytic disease of newborns (HDN)

341
Q

What are the consequences of HDN?

A

First child is usually not harmed, but during first birth mother can be exposed to child’s blood so she produces anti-Rh antibodies; if she exposed to the second child’s blood, IgG antibodies can destroy fetal blood cells

342
Q

Blood typing is done by

A

taking advantage of circulating IgM antibodies which are produced against foreign antigens but not against self

343
Q

How many blood groups have been identified?

A

over 20

344
Q

What is autologous blood donation?

A

when people stockpile their own blood before elective surgery bc they’re likely to mismatch

345
Q

What happens in a transfusion reaction? (3)

A

intravascular hemolysis of transfused RBCs is detected; results from IgM binding to foreign antigens and activating complement system; RBCs are destroyed via osmotic lysis

346
Q

What molecule is released during a transfusion reaction?

A

hemoglobin released from RBC is converted to bilirubin

347
Q

Describe bilirubin.

A

toxic and causes severe organ damage, especially to kidneys

348
Q

What is the major treatment to a transfusion reaction?

A

stop transfusion and administer large amounts of intravenous fluids to wash bilirubin out of body

349
Q

What are polyclonal antibodies?

A

Antibodies secreted by B-cells with many different specificities

350
Q

What are monoclonal antibodies?

A

antibodies that exhibit specificity for one epitope only

351
Q

How are polyclonal antibodies isolated in labs? (2)

A

Inject antigen into vertebrate; periodic bleeding of animal allows isolation of serum antibodies

352
Q

How are monoclonal antibodies isolated in labs?

A

mouse is immunized several times with antigen and killed; B lymphocytes which are now specific for antigen are harvested from mouse spleen; B cells fused with cancerous myeloma cells for immortality

353
Q

What is a hybridoma?

A

outcome of B-cell/myeloma cell fusion

354
Q

What does AIDS stand for?

A

acquired immunodeficiency syndrome

355
Q

AIDS is characterized in part by

A

destruction of Th cells

356
Q

How can AIDS be monitored?

A

by examining reactivity of patient’s leukocytes with a monoclonal antibody against CD4 (Th cell marker)

357
Q

For a pathogen to establish itself in a host, what must happen?

A

must evade both nonspecific and specific immune systems

358
Q

Influenza is known because

A

it alters its surface antigens and avoids immune system recognition

359
Q

What are the viral proteins expressed by the influenza virus? (2)

A

hemagglutinin (HA) and neuraminidase (NA)

360
Q

What is antigen drift?

A

Influenza virus has an RNA genome that is replicated by a viral RNA polymerase that lacks proofreading ability, which means mutations are likely to accumulate over time

361
Q

What is antigen shift?

A

sudden appearance of a new subtype of influenza in which HA and NA proteins are completely different

362
Q

Malaria is caused by what organism?

A

protozoan parasite Plasmodium that is transmitted when humans are bitten by Anopheles mosquito

363
Q

How does salmonella typhimurium commonly cause food poisoning?

A

can alternate between expression of two flagellar proteins so that antibodies for one protein can’t recognize the other

364
Q

How does mycobacterium tuberculosis cause illness?

A

once it is phagocytosed into macrophages, they inhibit the phagosome from fusing with lysozomes and successfully multiply within the macrophages

365
Q

Give two examples of bacteria that invade mucosal surfaces.

A

Neisseria meningitidis; Neisseria gonorrhoeae

366
Q

How do bacteria invade mucosal surfaces?

A

secrete proteins that degrade the IgA antibodies that protect the mucosal surface

367
Q

Particularly pathogenic strains of bacteria work by

A

blocking the binding of phagocytosis-induced complement protein Cb3, which slows the phagocytic response

368
Q

How does HIV work?

A

human immunodeficiency virus binds to CD4 proteins on Th cells and utilizes these proteins to get inside the Th cells

369
Q

(T/F) HIV only infects Th cells.

A

False, HIV can infect monocytes too since monocytes also express CD4.

370
Q

Once HIV enters and infects the Th cell, what happens?

A

releases replicated viruses to other Th cells such that they all become infected and die

371
Q

When is an individual considered to have AIDS?

A

when the Th cell levels drop dramatically

372
Q

How does the immune system initially respond to HIV infection?

A

produces anti-HIV antibodies and eliminates infected cells using Tc cells

373
Q

How does the HIV infection progress? (2)

A

eventually HIV kills Th cells more rapidly than can Th cells proliferate for memory purposes; HIV causes decrease in MHC class I expression on infected cells which makes them less likely to be earmarked for destruction

374
Q

What are the implications of HIV being a retrovirus?

A

HIV can integrate itself into a genome and hide in a latent form

375
Q

AIDS was first discovered when young men died of

A

pneumonia or Kaposi’s sarcoma

376
Q

Pneumonia generally affects

A

those who are immunosuppressed

377
Q

In 2010, how many people lived with HIV?

A

34 million

Biology 2312 (11 decks)

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