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Immunology and Infection > Immune System Overview > Flashcards

Immune System Overview Flashcards

1
Q

what did jenner do?

A
  • founded immunoglogy, discovered vaccination

- used cow pox to vaccinate against smallpox

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2
Q

what is commensalism?

A

one organism benefits and the other is unaffected

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3
Q

what is mutualism?

A

both organisms benefit

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4
Q

what is parasitism?

A

one organism benefits at the expense of the other

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5
Q

what are most bacteria in the body?

A

commensal organisms

- useful for fermentation, digestion and obsorption of nutrients

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6
Q

what is a pathogen?

A

an organisms that causes disease

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7
Q

what is an antigen?

A
  • molecule capable of inducing an immune response

- not always derived from a microbe

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8
Q

what are the mechanisms for protection?

A
  • physical barriers
  • innate immune system
  • adaptive immune system
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9
Q

what are physical barriers?

A

skin, respiratory tract, intestines

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10
Q

what is the innate immune system?

A
  • immediate - acts quickly

- recognises foreign pathogens via germ line receptors

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11
Q

what is the adaptive immune system?

A
  • takes days to develop
  • highly specific
  • generates memory
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12
Q

what is supposed to happen when a pathogen is encountered?

A
  • antimicrobial immune response
  • clearance
  • end of response
  • no or short pathoglogy
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13
Q

what is acute disease?

A
  • a cytopathic (cell destroying) pathogen leads to anti-microbial immune response, however, there is unsuccessful clearance of the pathogen
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14
Q

what is prolonged/chronic disease?

A
  • immune response not completely effective
  • not able to clear the pathogen and doesn’t stop
  • can affect your own tissue
  • prolonged attack of self
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15
Q

what is important about immune tisues?

A
  • they are strategically placed

- lymph nodes are near points of entry for the pathogens

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16
Q

what is the primary lymphoid?

A

thymus and bone marrow

- where immune cells develop

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17
Q

what is the secondary lymphoid?

A
  • where the immune response occurs

- eg spleen, lymph nodes, peyers patches

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18
Q

what is the bone marrow?

A

produce lots of different cells found in the bloodstream

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19
Q

what is the spleen?

A
  • filters the blood, 95% of blood filtered in 3 minutes
  • key in the reomval of damaged RBCs
  • highly organised structure that has areas rich in immune cells and areas rich in blood cells
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20
Q

what are the key features of the innate immune system?

A
  • immediate and no memory
  • antigen non-specific
  • can recognise bacteria but not a specific bacteria
  • often phagocytic cells
  • detect particulate materual, scavenge and remove
  • limited number of receptors that recognise broad molecular patterns
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21
Q

what is the role macrophages?

A
  • phagocytosis and activation of bacterial mechanisms
  • induces inflammation through the release of soluble factors
  • break down, in the lysosome
  • reside in peripheral tissues
  • first line of defence
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22
Q

what is the role of neutrophils?

A
  • most common white blood cells in the blood
  • migrate rapidly to the site of inflammation
  • phagicytic cells
  • release granules containing toxic compounds
  • first to arrive
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23
Q

what are the key features of the adaptive immune system?

A
  • antigen specific
  • B cells: antibodies
  • T cells: T helper and t killer cells
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24
Q

what is found on B cells?

A
  • antibodies found on B cells
  • they can be membrane bound or secreted
  • have a constant and a variable region
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25
Q

what is found on T cells?

A

T cell receptors

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26
Q

what is similar about BCRs and TCRs?

A

both are highly variable and can recognise many different antigens
- specificity confined to a single clone

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27
Q

give a simple explanation of how B and T cells work

A

become activated, expand, mature and differentiate to highly specialised cell populations

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28
Q

what are the antigen specific receptors on B and T cells?

A
  • Antibodies on B cells; can recognise 3D shapes o the antigen
  • TCRs on T cells; recognises protein in broken down form
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29
Q

what are dendritic cells?

A
  • interphase of innate and adaptive immunity
  • present linear peptides to T cells
  • phagocytic cells that degrade pathogens
  • main function is the activation of the adaptive immune response
  • migrate from peripheral tissues to the lymph node
  • survey the skin for pathogens
  • activetly transport antigens from the site of infection to the lymph node
  • one of the earliest signals of the immune response
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30
Q

what is the lymphatic system?

A
  • dendritic cells use a migration route
  • drain fluid from peripheral tissues
  • lymph nodes found at drainage points
  • very well organised
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31
Q

why do dentritic cells need to go the lymph nodes?

A

to interact with and activate antigen specific T cells

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32
Q

what are the 3 key steps of the adaptive immune system?

A
  1. activation of tissue dendritic cells
  2. migration to lymph node
  3. activation of antigen specific T helper cells
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33
Q

where do immune cells develop?

A

the thymus and the bone marrow (primary)

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34
Q

where does the immune response occur?

A

in the lymphoid tissues (secondary)

35
Q

where are lymphocytes initially selected for their purpose?

A

primary lymphoid organs

36
Q

where are lymphocytes ultimately armed?

A

secondary lymphoid organs

37
Q

when does effective specific armament of lymphocytes take place?

A

when the adaptive immune response are initiated eg response to infection

38
Q

where are the divergent weaponries of lymphocytes unleashed?

A

in the non-lymphoid target tissues

39
Q

what does functional adaptive immunity rewuire?

A

orchestrated interactions of different immune cells in specific micro-environments within primary and secondary lymphoid organs

40
Q

what does functional immunity require?

A

tightly regulated movment of immune cells between immune organs and non-lymphoid target tissues

41
Q

what are tertiary lymphoid organs?

A

organised structures of lymphocytes in target tissues and organs

42
Q

where do T cells develop?

A

Thymus

43
Q

where do B cells develop?

A

Bone Marrow

44
Q

what is haematopoiesis?

A

haematopoietic stem cells gives rise to many different lineages

45
Q

what do HSCs form?

A
  • they self renew
  • become less and less flexible
  • lymphoid lineages, line of differentiation
46
Q

where is haematopoiesis in foetal life?

A
  • yolk sac from week 4 development
  • liver until shortly before birth
  • in the spleen until cartilaginous bones vascualrised
47
Q

where is haematopoiesis in adult/infant life?

A
  • bone marrow of most bones in children

- mainly in pelvis, stenrum vertebrate and cranium in adults

48
Q

where is haematopoiesis in adult life?

A
  • emergency haematopoiesis
  • occurs in the spleen, liver and lymph nodes
  • extramedullary haematopoiesis
49
Q

what is the structure of the thymus?

A
  • tow lobed organ
  • superior to the heart
  • framework of epithelial cells that house lymphocytes
  • two lobes surrounded by a capsue
  • trabeculae/septa
  • cortex
  • medulla
50
Q

how many T cell pre-cursors become T cells?

A

only 2% of T cell pre-cursors that arrive in the thymus achieve the proper ‘education’ to become mature T cells

51
Q

what is the focus of T cell training?

A

recognising self and non-self

52
Q

what is the trabeculae/septa of the thymus?

A

extensions of the capsule into the cortex and medulla that establish open thymic lobules where blood vessels and nerves pass

53
Q

what is the cortex of the thymus?

A
  • outer layer that contains many immature thymocytes

- high concentration of maturing T cells

54
Q

what is the medulla of the thymus?

A

the inner layer of mature T cells and Hassall’s corpuscles

55
Q

what is thymic involution?

A
  • with ageing there is a decrease in size of thymus and production of naive T cells
  • linked to decreased immune function in elderly
56
Q

what are some secondary lymphoid organs?

A
  • lymph nodes
  • spleen
  • MALT, GALT, NALT
57
Q

what is the structure of the spleen?

A
  • largest lymphoid organ
  • highly organised
  • red pulp
  • white pulp
  • PALS
58
Q

what is the function of the spleen?

A
  • directs immune response to antigens in the blood
  • important for the clearance of RBCs
  • engorged spleen common in chronic inflammatory diseases
59
Q

what is white pulp?

A
  • areas rich in immune cells

- contains specific lymphoid micro-environment

60
Q

what is red pulp?

A
  • areas rich in RBCs
  • filters the blood
  • removes old RBC and other cells from the blood
  • contains macrophages
  • carries out extramedullary haematopoiesis
61
Q

what is PALS?

A
  • periarteriolar lymphoid sheath

- proliferating lymphocytes around central arterioles which are branches of the splenic artery

62
Q

what is the role of the lymphatic system?

A
  • a draining system; fluid balance, returning to the blood
  • excess interstitial fluid
  • plasma proteins
63
Q

what are lymph capillaries?

A
  • originate as ‘closed tubules’ in almost all tissues

- capillary wall constructure of overlapping endothelial cells that respond to fluid pressure

64
Q

what do lymphatic vessels carry?

A

lymph and cells from peripheral tissues to draining lymph node

65
Q

what is lymph?

A

plasma containing proteins and solutes that filter out of venules and capillaries due to hydrostatic pressure
- tissue derived pathogens may be carried in lymph

66
Q

what are superficial lymphatics?

A
  • follow superficial veins
  • flow into lymph nodes in axillary, inguinal or cervical areas
  • drain into deep lymphatics
67
Q

what are deep lymphatics?

A
  • lymph nodes either side of aorta drain the paired organs, nodes lying anterior to the gut
  • thoracic dust, largest vessel
68
Q

what is the structure of lymph nodes?

A
  • pea sized immune structures
  • cells arrive; afferent
  • cells exit; efferent
69
Q

what is the role of the lymph node?

A
  • component of host defense
  • filter components
  • meeting place for immune cells and antigens
70
Q

what is the B cell rich area in the lymph node?

A

follicle

71
Q

what is the primary follice?

A

mature, naive B cells

72
Q

what is the secondary follice?

A

germinal centre reaction

73
Q

what are germinal centres?

A
  • develop in response to stimulation

- site of B cell proliferation, selection, affinity maturation and differentiation

74
Q

what is the T cell rich area in the lymph node?

A

paracortex

75
Q

what do naive lymphocytes enter the lymph nodes through?

A

high endothelial venules (HEVs)

76
Q

how do APCs use the lymph nodes?

A
  • enter

- scan for lymphocytes

77
Q

what happens if an APC is recognised by a T cell?

A

multiplies and expands

- helps the B cells

78
Q

by what process are B and T cells separated in the lymph node?

A
  • membrane receptors pulling the cell towards areas rich in their ligands
  • chemotaxis
  • cells produce distinct chemokines that attract B or T cells so they segregate
79
Q

how are B cells attracted in the lymph node?

A
  • B cell areas rich in CXCL13

- The ligand of CXCR5 on B cells

80
Q

how are T cell attracted in the lymph node?

A
  • T cells areas rich in CCL21 and CCL19
  • the ligands of CCR7 (receptor on T cells and dendritic cells)
  • T cells move and stay there
81
Q

what is chemotaxis?

A

directed movement in response to chemicals

- chemoattractant forms a gradient

82
Q

what are chemokines?

A

chemotactic cytokines (secreted soluble proteins)

83
Q

what is MALT?

A
  • mucosa associated lymphoid tissues

- large organised aggregates of lymphoid tissue in the digestive, respiratory and genitourinary tracts

84
Q

what are Peyers patches?

A
  • organised aggregates of lymphoid cells in the ileum
  • monitor bacteria populations and prevents pathogen growth in the intestine
  • large population of antibody producing plasma cells

Immunology and Infection (13 decks)

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