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Introductory Microbiology > Host defenses > Flashcards

Host defenses Flashcards

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1
Q

What is innate defences

A

properties of the normal host, non-specific defenses

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2
Q

What is adaptive defenses

A

Induced by the infection, specific to the pathogen (based on antogen)

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3
Q

First barrier to the pathogen is

A

Innate defenses

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4
Q

some innate defenses of our organism

A
  • Removal of particles
  • Skin
  • Lysozyme ( tears and other secretions)
  • Mucus and cilia lining trachea
  • Blood and lymph
  • Flushing urinary tract
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5
Q

What does innate defenses of skin and mucous membrane

A

Normal microbiome

Antimicrobial substances

Skin

Mucous

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6
Q

describe how normal microbiome in the gut acts as an innate defense

A

Competes for attachment sites and nutrients, secretes bacteriocin (a toxic protein secreted by
bacteria that inhibits or kills other, related
bacteria)

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7
Q

describe how antimicrobial substances on the skin acts as an innate defense

A

Fatty acids
Lysozymes
Antimicrobial peptides(AMPs)
antibodies ( if the host is immune)

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8
Q

How do AMPs work

A

Make pores in the bacterial membrane

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9
Q

How does skin and mucous membrane protects the host

A

Skin: thick layer of dead cells

Mucous membrane: mucus

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10
Q

Describe the innate defenses of the airways

A

Mucous membrane; mucus traps bacteria; ciliated cells remove mucus and trapped bacteria

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11
Q

What is the second line of defenses

A
  • Complement system
  • Phagocytes
  • Inflammation
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12
Q

What is a complement system

A

Set of proteins that creates pores in the pathogen membrane and induces lysis

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13
Q

What are phagocytes

A

Cells that take up and digest pathogens

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14
Q

What is an inflammation

A

General nonspecific response of the innate system to toxins, pathogens and tissue damage

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15
Q

Why complement system is called like that

A

They complement the action of antibodies

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16
Q

Proteins of complement system

A

C1-C9

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17
Q

Two activation pathways of complement systems

A
  • Activation by he classical pathway :antibodies

- Activation by the alternative pathway: microbial cell wall components (polysaccharide, lipopolysaccharide)

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18
Q

Activation of the complement results in the formation of

A

A membrane attack complex (MAC) that causes lysis of some Gram-negative, no effect on Gram-positive

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19
Q

MAC complex. What doe sit consist of and how it is formed

A

C5bC6789

C5b C6 and C7 come together and bind to the membrane. C8 binds to the complex and inserts into the cell membrane. Then C9 ( mutiple) comes and polymers around the complex, creating a pore-> lysis

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20
Q

How do you test if the pathogen can be destroyed by the complement system

A

Test by exposing pathogens to serum (blood without RBC)

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21
Q

What is the pathway of differentiation of the steam cell

A

Hematopoietic stem cell will develop into Myelold precursor and Lymphoid precursor

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22
Q

What happens after myelold precursor cells

A

Manocyte->dendritic cell or macrophage

Granulocytes->Neutrophill or Mast cell

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23
Q

What happens after Lymphoid precursor

A

Maturation in bone marrow-> B -cells->plasma cells

or from lymphoid to natural killer cells and T cells

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24
Q

What cells are in innate immunity

A

Dendritic cell, macrophage, neutrophile and mast cell

Natural killer cells

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25
Q

which cells are in adaptive immunity

A

T cell

Plasma cell

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26
Q

4 major cell types found in normal human blood

A 
RBCs
Lymphocytes (WBCs) which include:
Neutrophil
Monocyte
Leukocytes
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27
Q

What are monocytes

A

Circulate in the blood stream, differentiate into macrophages ( and dendritic cells) in tissues, attracted to inflamed tissues, phagocytic. Macrophages are present in all tissues and take on different forms in different tissues

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28
Q

Granulocytes include what cells in itself

A

Eosinophils
Basophils
Neutrophils
Mast cells

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29
Q

Neurtophiles are ___, their property and the other name

A

They are the most abundant, phagocytic, often called polymorphonuclear leucocytes (PMNs)

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30
Q

Lymphocytes include in itself

A

B cells: antibodies

T cells: T helper cells, cytotoxic T cells

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31
Q

Granulocytes have____

A

bleach and other antimicrobial agents that are phagocytic

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32
Q

What are the most abundant WBCs

A

Neutrophiles

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33
Q

WBCs circulate around in

A

The blood and in the lymph

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34
Q

Lymph nodes have

A

Phagocytes and lymphocytes

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35
Q

Phagocytosis is primarily carried by

A

Netrophiles and macrophages

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36
Q

Explain the process of phagocytosis

A
  1. Attachment of the organism to the membrane of the phagocyte
  2. Ingestion: the organism become enclosed in a phagosome
  3. A) granules (endosomes, lysosomes) containing hydrolytic enzymes fuse with the phagosome, formation of the phagolysosomes
    B) Oxidative burst: production of reactive oxygen species
  4. Killing and digestion of the microorganism
37
Q

Explain how generation of toxic reactive oxygen species happen

A

Oxidative burst: rapid increase in uptake of O2-> produces ROS (O2, H2O2, OH,OCl-)

38
Q

What are important enzymes for oxidative burst

A
  • Myeloperoxidase
  • NADPH oxidase
  • V-type ATPases (Pumps H+ in)
39
Q

What is inflammation

A

A non-specific response to tissue damage or the presence or of microorganisms

40
Q

Characteristics signs of inflammation

A

Redness, heat, swelling and pain

41
Q

Why there is redness and heat during inflammation

A

Redness and heat are due to vasodilatation- enlargement of the blood vessels

42
Q

Why there is swelling during inflammation

A

Swelling is due to the passage of fluid (plasma) from blood vessels to the tissues from increased vascular permeability (vasodilatation). Plasma contains antimicrobial proteins

43
Q

What is the function of inflammation

A

It allows the recruitment of immune cells to the site of infection (vascular permeability) and an increase concentration of molecules (complement subunits and antibodies)

44
Q

What role complement system plays in vasodilatation

A

C3a causes the release of histamine by mast cells-> acts to increase permeability of blood vessels
C5a attracts phagocytes to infected tissues

45
Q

What is a diapedesis

A

Passage of white blood cells through the intact walls of the capillaries

46
Q

What is the role of interleukin-1 in inflammation

A

There is an increase movement of fluid and immune cells to the infection sites. Il-1 activate cells of the immune system ( increase phagocytosis)

Il-1 acts on the thermoregulatory center of the brain , which in turn causes the body temperature to increase

47
Q

What is the response to the presence of endotoxins (LPS)

A

Macrophages can sense endotoxins-> induce production of fever-producing (pyrogen) signaling molecules: the cytokine Interleukin-1.

48
Q

What temperature is usually for the inflammation response and what of higher (precaution)

A

Temperature higher that 37C reduce the growth of some pathogens

Death if temperature reaches 44C

49
Q

The innate defenses have

A
  • Complement
  • Antimicrobial proteins
  • Phagocytes (neutrophils, macrophage)
  • Inflammation (and fever)
50
Q

What is happens first to the infection and what is happening after

A

During infection, the adaptive defenses are being primed. If the infection is prolonged, adaptive immunity will be called upon to help in the fight against the invading microorganisms

51
Q

What are antigens

A

Molecules of the microorganisms that can be recognized by the immune system

52
Q

Adaptive defenses rely on

A

The detection and response to foreign antigens

53
Q

Cells of the adaptive immune system

A

B cells, T cells and antigen presenting cells (APCs: macrophages, dendritic cells; important for activation of the adaptive defense)

54
Q

In Population of T cells and B cells each cell is specific for

A

One antigen

55
Q

What will happen to T cells and B cells that were activated by the antigen

A

Produce copies of themselves. If activated by X antigen, then cells that are specific for it, will multiply

56
Q

How antigen specificity is generated in T cells and B cells

A

Randomly during the development

57
Q

T cells and B cells that recognize host antigen are

A

Destroyed

58
Q

Two types of T cells

A

T helper cells : activate B cells and macrophages

Cytotoxic T cells: kill host cells that display foreign antigen on their surfaces

59
Q

Who present antigen to T cells

A

APCs- macrophages, dendritic cells

60
Q

WHat will happen after presenting an antigen to T cell

A

the T cell will become activated and produce interleukin 2 (Il-2). This induces multiplication and differentiation into effector T cells and memory T cells

61
Q

Explain MHC I complex antigen presentation

A

If there is a foreign protein in the cytoplasm ( due to the viral infection or cancer cells), the goal is to present this protein to the surface of the cell.

Proteasome break peptide bonds in the protein. Through TAP the wrong protein gets to ER. in ER with MHCI, chaperonin and other proteins, the shady protein is carried outside of the cell for presenting

62
Q

What cells have MHC I complex

A

All cells with nucleus, except RBCs

63
Q

The difference between MHC I and MHC II

A

MHC I -infected target cells . Thee antigen was not present outside. It is taken from inside to outside for presentation

MHCII happens in APCs. Through the endocytosis the foreign substance is presented

MHC I recognized by Tc
MHC II recognized by Th

64
Q

Explain how MHC II presentation happens

A

The foreign protein was taken in by endocytosis, bound to MHC II on ER. After that it was moved to phagolysosome, where it would be digested and parts of the antigen protein would be presented on the surface of the antigen presenting cell

65
Q

What is MHC

A

The major histocompatibility complex

66
Q

What cells MHC II

A

APCs: macrophages, Dendritic cells, B cells

67
Q

What happens after MHC 1 presents an antigen

A

Tc releases perforins and granzymes that kill the cell through apoptosis

68
Q

MHC I system and Tc are helpful against

A

Infection by viruses /intracellular pathogens

69
Q

What happens after Th are activated by MHC II

A

Th cell can help activate macrophages (TNF-alpha) that are presenting antigens for which the T cell is specific.

Activated macrophages have increased phagocytic activity and produce much higher levels of hydrolytic enzymes. Often referred to as “angry killer cells”

70
Q

MHCII and T helper cells are very important against

A

Bacterial pathogens (especially against intracellular pathogens of macrophages)

71
Q

Explain the pathway from bone marrow to antibody (b cells)

A

Bone marrow stem cell-> B cells with different antibodies

When a specific antigen binds to antibodies, the activated B cells multiplies and differentiate into plasma B cells and memory cells

Plasma b cells-> produce antibodies

72
Q

How the activation of B cells happen

A

The B cell displays its antibody on its surface. Acts as a receptor to pick the foreign antigen it recognizes, This antigen will be processes and displayed on its surface by MHC II

A pre-activated T cell specific for the antigen recognizes this complex (MHCII-antigen) and activates the B cell (Il-4). The T cell was previously activates by APC

The B cell multiplies and differentiates into plasma cells (produce the antibody) and memory cells (waiting for the next exposure to the antigen)

73
Q

What is an antibody

A

Group of related proteins-immunoglobulins

Have two sites: antigen binding sites (Fab) -highly variable

AND

Constant region (Fc) binds to receptor on macrophages and activates complement (classical pathway)

74
Q

Types of antibodies

A

IgA
IgG
IgM
IgE

75
Q

IgG: where does it circulate and characteristics

A

Major circulating antibody, most abundant. Found in lymph, blood and extracellular fluid

76
Q

IgM: characteristics, where found, what causes

A

First antibody to appear. Found in blood and lymph only. Causes aggregation of antigens and helps in early complement activation

77
Q

IgA: where it is found, what does it do

A

Secretory antibody, found in extracellular body fluids and in mucus. Main mediators of mucosal immunity

78
Q

IgE: function, characteristics

A

Least abundant, main function os immunity to parasites. Essential role in hypersensitivity and various allergies (food allergy)

79
Q

Function of antobodies

A

Function as opsonins, which increase phagocytosis efficiency.

Bind to toxins , which prevents binding of toxin to host cells

Bind to adhesins, which prevents of microorganism to host cel

80
Q

The role of memory cells

A

They ensure the immune response, following a second exposure to the same antigen, is faster and stronger

81
Q

Antibodies produced during primary and secondary responses

A

Initial contact at day 0 initiates a primary immune response

After several days, IgM antibody is produced at detectable but low titers.

In the absence of antigen , the titer decreases with time

Another contact with the same antigen -> secondary immune response.

Antibody class switches rapidly to IgG, produced in high amounts

82
Q

What is active immunity

A

Involves the production of memory cells in response to antogenic stimulus

83
Q

Two types of active immunity

A
  • Natural:following infection

- Artifical: vaccination (live, attenuated, dead agents or subunit: adhesins, capsular polysaccharide toxoids)

84
Q

What is passive immunity

A

Involves the acquisition of preformed antibodies

85
Q

Two types of passive immunity

A
  • Natural: placentral transfer or colostrum (first form of milk)
  • Artificial: serum from an immune animal
86
Q

Why do we do vaccination

A

Activation of B cells might take few days, vaccination -> immediate response

87
Q

What is natural immunity and its examples in animals and humans

A

Humans are naturally resistant to many infectious diseases of lower animals and vice versa:

Actinobacillus pleuropneumoniae causes pleuropneumoniae in pigs but does not cause diseases in humans

Salmonella typhi causes typhoid only in humans

88
Q

How natural immunity can be explained

A

In part by the absence or presence of the appropriate receptors in the animal for the adhesins expressed by the pathogen (same rationale for toxins and other virulence factors)

Introductory Microbiology (21 decks)

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