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white blood cells Flashcards

1
Q

what is innate immunity?

A

rapid re-programmed response to a broad range of microbes

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2
Q

what are characteristics of innate immunity?

A

o No time lag
o Not antigen specific
o No memory

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3
Q

what is acquired immunity?

A

slower learnt responses to specific microbes

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4
Q

what are characteristics of acquired immunity?

A

o Lag period
o Antigen specific
o Development of memory

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5
Q

where is IgA found?

A

found in mucosal areas, such as gut, respiratory tract and urogenital tract

Also in saliva, tears, and breast milk.

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6
Q

what is the function of IgA?

A

Prevents colonization by pathogens

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7
Q

what is the function of IgD?

A

mainly acts as an antigen receptor on B cells that haven’t been exposed to antigens

Shown to activate basophils and mast cells to produce antimicrobial factors

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8
Q

what are the functions of IgE?

A

Binds to allergens + triggers histamine release from mast cells + basophils.
o Involved in allergy.
o Protects against parasitic worms

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9
Q

why is IgE less common in serum?

A

bc it binds tightly to basophils and mast cells before interacting with antigen

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10
Q

what is the function of IgG?

A

provides majority of antibody-based immunity against invading pathogens

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11
Q

what is the most common antibody?

A

IgG

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12
Q

how is IgM found?

A

monomer on the B cell surface

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13
Q

what is the structure of secreted IgM?

A

pentamer

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14
Q

what is the function of IgM?

A

Eliminates pathogens in early stages of humoral immunity before there’s enough IgG

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15
Q

what is the first antibody to be made?

A

IgM

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16
Q

what are epitopes?

A

fragments of protein presented on the surface of cells

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17
Q

where do all cells present their epitopes?

A

MHC1 site

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18
Q

where are foreign epitopes displayed?

A

MHC2 site

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19
Q

where are MHC2 sites found?

A

only on APCs

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20
Q

what do foreign epitopes do?

A

stimulates certain immune cells attracted to the site by chemokines to make antibodies specific to the FE

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21
Q

what do antibodies do?

A

Antibodies bind to the original pathogens and help the immune cell recognise and attack the pathogens

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22
Q

where do granulated WBCs come from?

A

myeloblasts in the myeloid cell line

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23
Q

what do monocytes differentiate into?

A

macrophages

dendritic cells

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24
Q

what are sentinels?

A

lookout cells

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25
Q

how do macrophages move around?

A

amoeboid movement

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26
Q

what do macrophages do?

A
  • Engulf and digest cellular debris, foreign substances + microbes by phagocytosis
  • Meanwhile they also send out chemokines that attract other WBCs to infection site
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27
Q

what are alveolar macrophages?

A

move around inside alveoli – remove dust particles that have evaded the mucus lining in the upper airways

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28
Q

what are osteoclasts?

A

found in bone. Remove debris from bone breakdown

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29
Q

what are histiocytes?

A

generic name for tissue resident macrophages

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30
Q

where are Kupffer cells found?

A

liver

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31
Q

where are microglia cells found?

A

brain

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32
Q

where are intestinal macrophages found?

A

gut

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33
Q

what are toll like receptors?

A

Proteins on the surface membrane of macrophages

Can bind to many antigens found on bacteria/fungi surfaces

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34
Q

how do macrophages kill bacteria?

A
  • macrophages send out pseudopods w TLRs on the end
  • stick to bacteria, retract and engulf bacteria into a phagosome
  • phagosome and lysosome fuse to make phagolysosome
  • digestive enzymes secreted into phagolysosome and break down and digest bacteria cell wall
  • kill bacteria and indigestible material is ejected
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35
Q

what is a lysosome?

A

small membrane bound sacs of digestive+other enzymes

36
Q

name a defence mechanism of TB

A
  • have a waxy material in their cell wall that resists penetration by the lysosome enzymes
  • can be phagocytosed by cant kill them fast enough to stop replication so they can grow inside the lysosomes
37
Q

describe the structure of a ghon focus

A
  • at the centre is a caseous necrosis
  • layer of macrophages surround this - trying to ingest the bacteria
  • surrounded by lymphocytes which try and kill any escaping bacteria
  • ring of fibroblasts
  • calcium on outer layers
38
Q

what is the caseous necrosis?

A

mass of dead tissue containing live TV bacteria found in the centre

39
Q

what are dendritic cells?

A

specialised type of macrophage

40
Q

where are dendritic cells found?

A

• Present in tissues that are in contact with the external environment e.g. skin, inner lining of the nose, lungs, stomach and intestines

41
Q

describe the structure of dendritic cells

A

Have extensive membrane processes - can be finger-like projections or folded into sheets –> large surface area to expose TLRs

42
Q

how do dendritic cells stimulate B cells to make antibodies?

A

TLRs of dendritic cells bind to bacterium, phagocytose and break down bacterial cell wall

  • epitope presented and they move to a lymph node
  • display bacterial epitope to T helper cell –> stimulates B cells to make antibodies to the epitope
43
Q

what antibody do dendritic cells have on their membrane?

A

IgG

44
Q

what are langerhan cells?

A

Dendritic cells found in the dermis, epidermis, mucosa of the mouth, foreskin and vaginal epithelium. Can be found in other tissues such as lymph nodes

45
Q

what role do Langerhan cells play in skin infections?

A

In skin infections, local Langerhan cells take up and process microbial antigens to become APCs

46
Q

what is Langerin and what is its suggested role?

A
  • Langerin – lectin (carbohydrate binding protein) made by Langerhan cells
  • Suggested langerin in the genital epithelium protects against HIV-1
47
Q

what are mast cells?

A

• Granulocytes that are formed directly from the common myeloid progenitor cell line

48
Q

what is the function of mast cells?

A

Act as sentinels in tissues, esp near/in epithelial surfaces in the respiratory tract – detect pathogens that are inhaled

49
Q

what do mast cells contain?

A

histamine and heparin

50
Q

what is found on the surface of mast cells?

A

• Have TLRs on the membrane but can also display various classes of antibodies – enable mast cells to bind to known antigens

51
Q

how do mast cells help in allergic reactions?

A

• Antigen binding triggers degranulation of mast cells – release histamine and other cytokines

52
Q

what % of WBCs are neutrophils?

A

60%

53
Q

what is neutropenia?

A

low neutrophil count

54
Q

what type of white blood cell are neutrophils?

A

granulated leucocytes

55
Q

what are polymorphonuclear leucocytes?

A

When released from bone marrow its spherical and its nucleus has 3-4 lobes

56
Q

what causes neutrophil activation?

A

contact with chemokines by sentinel cells - attracts them to the site

57
Q

what happens to the neutrophil when its activated?

A
  • Changes shape –> amoeba like and can extend pseudopods
  • Number of lobes of the nucleus increases – sometimes to 6 or more bc of increased protein production – specifically of granules for release on to pathogens
58
Q

describe the stages of neutrophil migration

A
  • activated neutrophils become amoeboid and attach to the endothelium
  • roll along it and squeeze between the endothelial cells into extra-cellular space
  • chemotaxis guides them to site
  • stimulation of TLRs and IgG on surface causes release of granules
  • adhesion depends on selectin and integrin proteins
59
Q

what process guides neutrophils to the site of bacterial infection?

A

chemotaxis

60
Q

what causes the release of granules from neutrophils?

A

stimulation of TLRs and IgG on their surface

61
Q

what does neutrophil adhesion depend on?

A

selectin and integrin proteins

62
Q

what are the 3 main methods for directly attacking micro-organisms?

A
  • phagocytosis
  • degranulation
  • generation of neutrophil extracellular traps (NETs)
63
Q

name some enzymes that neutrophil granules contain.

what other molecules do they contain?

A

myeloperoxidase, bactericidal-permeability-increasing protein (BPI), defensins, and the serine proteases neutrophil elastase and cathepsin G

also contain molecules that make ROS e.g. peroxides

64
Q

what happens to neutrophils once they’ve released their granules?

A

they die by apoptosis - causes release of web-like structures of chromatin and serine proteases – trap bacteria and kill them

65
Q

what process does the release of neutrophil granules cause?

A

triggers local inflammation in the infected tissue

66
Q

define inflammation

A

process occurs locally in vascularised tissue which is designed to destroy/remove pathogens and to initiate repair of damaged tissue

67
Q

what are the 5 signs of inflammation?

A

redness, heat, pain, swelling, loss of function

68
Q

describe the process of inflammation and what causes each of the signs of inflammation

A
  • Sentinels detect pathogens via TLRs –> release chemokines –> trigger neutrophils to migrate to pathogen site
  • Histamine from mast cells increases local vascular permeability –> allows fluid, protein, phagocytic neutrophils to enter the infected tissue –> swelling and reddening of the tissue
  • Increased blood flow to the site makes it feel warm
  • These events cause pain – stimulates nociceptors in the tissue
69
Q

what happens if neutrophils and macrophages dont kill the bacteria?

A

basophils migrate out of the blood into infected tissue

70
Q

what are basophils

A

granulocytes that stain blue in standard blood stains

71
Q

what % of WBCs are basophils?

A

0.5-1%

72
Q

what is the main difference between basophils and mast cells?

A

main difference is that mast cells have more granules

73
Q

what do the basophil granules contain and what do these compounds do?

A

o Serotonin makes capillary ends constrict
o Histamine increases vascular permeability
o Both cause increased extravasation of plasma + increase migration of WBCs to infection site
o Heparin prevents clots forming in the capillaries of infected areas

74
Q

what do eosinophils arise from?

A

myeloblasts

75
Q

what % of WBCs do eosinophils make up?

A

1-3% of WBCs

76
Q

where are eosinophils found normally and in disease?

A

lower GI tract, ovaries, uterus, spleen + lymph nodes

o In normal conditions they’re NOT found in; lungs, skin, oesophagus – associated w disease

77
Q

what is the main role of eosinophils?

A

attack multicellular parasites e.g. plasmodium species/intestinal worms (hence why they’re in the gut). Can also trigger asthma and allergy mechanisms

78
Q

what chemicals do eosinophils contain?

A

• Contain powerful chemicals e.g. peroxidases + enzymes to kill cells inc ribonucleases, deoxyribonucleases, lipases, plasminogen and major basic proteins

79
Q

what are eosinophil granules released?

A

released following activation by contact with parasites

80
Q

how are osteoclasts formed?

A
  • Derived from macrophages + monocytes – migrate into bone to become osteoclast progenitor cells – express RANK (receptor activator of nuclear factor kappa B)
  • RANKL (ligand for RANK) expressed by resident bone cells e.g. osteoblasts + osteocytes – triggers differentiation of osteoclast progenitor cell into osteoclast
81
Q

what is osteoprotegerin?

A

inhibits osteoclast formation – produced by osteoblasts and binds to RANKL so macrophages/monocytes can’t interact with it.

82
Q

what are NK cells?

A

Large granular lymphocytes – arise from common lymphoid progenitor cell line

83
Q

how do self-epitopes affect NK cells?

A

activate an inhibitory receptor on the NK cell – prevents attack by NK

84
Q

how do NK cells know to attack infected cells?

A

• Cells with viruses in them have additional fragments of viral protein on their epitope on the MHC1 that they’ve been forced to manufacture  disable inhibitory receptor  NK attacks infected cell

85
Q

why are NK cells important in the respiratory system?

A

NK cells are rlly important in the respiratory system bc they can kill cells infected with an inhaled virus

86
Q

how do NK cells kill infected cells?

A

NK cell attaches to the target cell and releases perforin – creates hole in the cell membrane
• NK cell then injects granzyme enzymes through the pore into the target cell cytoplasm
• Granzyme activates caspases – trigger apoptosis of target cell  death of target cell and contained viruses

c2 (37 decks)

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