Immune System Overview Flashcards
1
Q
what did jenner do?
A
- founded immunoglogy, discovered vaccination
- used cow pox to vaccinate against smallpox
2
Q
what is commensalism?
A
one organism benefits and the other is unaffected
3
Q
what is mutualism?
A
both organisms benefit
4
Q
what is parasitism?
A
one organism benefits at the expense of the other
5
Q
what are most bacteria in the body?
A
commensal organisms
- useful for fermentation, digestion and obsorption of nutrients
6
Q
what is a pathogen?
A
an organisms that causes disease
7
Q
what is an antigen?
A
- molecule capable of inducing an immune response
- not always derived from a microbe
8
Q
what are the mechanisms for protection?
A
- physical barriers
- innate immune system
- adaptive immune system
9
Q
what are physical barriers?
A
skin, respiratory tract, intestines
10
Q
what is the innate immune system?
A
- immediate - acts quickly
- recognises foreign pathogens via germ line receptors
11
Q
what is the adaptive immune system?
A
- takes days to develop
- highly specific
- generates memory
12
Q
what is supposed to happen when a pathogen is encountered?
A
- antimicrobial immune response
- clearance
- end of response
- no or short pathoglogy
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
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
15
Q
what is important about immune tisues?
A
- they are strategically placed
- lymph nodes are near points of entry for the pathogens
16
Q
what is the primary lymphoid?
A
thymus and bone marrow
- where immune cells develop
17
Q
what is the secondary lymphoid?
A
- where the immune response occurs
- eg spleen, lymph nodes, peyers patches
18
Q
what is the bone marrow?
A
produce lots of different cells found in the bloodstream
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
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
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
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
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
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
25
what is found on T cells?
T cell receptors
26
what is similar about BCRs and TCRs?
both are highly variable and can recognise many different antigens
- specificity confined to a single clone
27
give a simple explanation of how B and T cells work
become activated, expand, mature and differentiate to highly specialised cell populations
28
what are the antigen specific receptors on B and T cells?
- Antibodies on B cells; can recognise 3D shapes o the antigen
- TCRs on T cells; recognises protein in broken down form
29
what are dendritic cells?
- 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
30
what is the lymphatic system?
- dendritic cells use a migration route
- drain fluid from peripheral tissues
- lymph nodes found at drainage points
- very well organised
31
why do dentritic cells need to go the lymph nodes?
to interact with and activate antigen specific T cells
32
what are the 3 key steps of the adaptive immune system?
1. activation of tissue dendritic cells
2. migration to lymph node
3. activation of antigen specific T helper cells
33
where do immune cells develop?
the thymus and the bone marrow (primary)
34
where does the immune response occur?
in the lymphoid tissues (secondary)
35
where are lymphocytes initially selected for their purpose?
primary lymphoid organs
36
where are lymphocytes ultimately armed?
secondary lymphoid organs
37
when does effective specific armament of lymphocytes take place?
when the adaptive immune response are initiated eg response to infection
38
where are the divergent weaponries of lymphocytes unleashed?
in the non-lymphoid target tissues
39
what does functional adaptive immunity rewuire?
orchestrated interactions of different immune cells in specific micro-environments within primary and secondary lymphoid organs
40
what does functional immunity require?
tightly regulated movment of immune cells between immune organs and non-lymphoid target tissues
41
what are tertiary lymphoid organs?
organised structures of lymphocytes in target tissues and organs
42
where do T cells develop?
Thymus
43
where do B cells develop?
Bone Marrow
44
what is haematopoiesis?
haematopoietic stem cells gives rise to many different lineages
45
what do HSCs form?
- they self renew
- become less and less flexible
- lymphoid lineages, line of differentiation
46
where is haematopoiesis in foetal life?
- yolk sac from week 4 development
- liver until shortly before birth
- in the spleen until cartilaginous bones vascualrised
47
where is haematopoiesis in adult/infant life?
- bone marrow of most bones in children
| - mainly in pelvis, stenrum vertebrate and cranium in adults
48
where is haematopoiesis in adult life?
- emergency haematopoiesis
- occurs in the spleen, liver and lymph nodes
- extramedullary haematopoiesis
49
what is the structure of the thymus?
- 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
how many T cell pre-cursors become T cells?
only 2% of T cell pre-cursors that arrive in the thymus achieve the proper 'education' to become mature T cells
51
what is the focus of T cell training?
recognising self and non-self
52
what is the trabeculae/septa of the thymus?
extensions of the capsule into the cortex and medulla that establish open thymic lobules where blood vessels and nerves pass
53
what is the cortex of the thymus?
- outer layer that contains many immature thymocytes
| - high concentration of maturing T cells
54
what is the medulla of the thymus?
the inner layer of mature T cells and Hassall's corpuscles
55
what is thymic involution?
- with ageing there is a decrease in size of thymus and production of naive T cells
- linked to decreased immune function in elderly
56
what are some secondary lymphoid organs?
- lymph nodes
- spleen
- MALT, GALT, NALT
57
what is the structure of the spleen?
- largest lymphoid organ
- highly organised
- red pulp
- white pulp
- PALS
58
what is the function of the spleen?
- directs immune response to antigens in the blood
- important for the clearance of RBCs
- engorged spleen common in chronic inflammatory diseases
59
what is white pulp?
- areas rich in immune cells
| - contains specific lymphoid micro-environment
60
what is red pulp?
- areas rich in RBCs
- filters the blood
- removes old RBC and other cells from the blood
- contains macrophages
- carries out extramedullary haematopoiesis
61
what is PALS?
- periarteriolar lymphoid sheath
| - proliferating lymphocytes around central arterioles which are branches of the splenic artery
62
what is the role of the lymphatic system?
- a draining system; fluid balance, returning to the blood
- excess interstitial fluid
- plasma proteins
63
what are lymph capillaries?
- originate as 'closed tubules' in almost all tissues
| - capillary wall constructure of overlapping endothelial cells that respond to fluid pressure
64
what do lymphatic vessels carry?
lymph and cells from peripheral tissues to draining lymph node
65
what is lymph?
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
what are superficial lymphatics?
- follow superficial veins
- flow into lymph nodes in axillary, inguinal or cervical areas
- drain into deep lymphatics
67
what are deep lymphatics?
- lymph nodes either side of aorta drain the paired organs, nodes lying anterior to the gut
- thoracic dust, largest vessel
68
what is the structure of lymph nodes?
- pea sized immune structures
- cells arrive; afferent
- cells exit; efferent
69
what is the role of the lymph node?
- component of host defense
- filter components
- meeting place for immune cells and antigens
70
what is the B cell rich area in the lymph node?
follicle
71
what is the primary follice?
mature, naive B cells
72
what is the secondary follice?
germinal centre reaction
73
what are germinal centres?
- develop in response to stimulation
| - site of B cell proliferation, selection, affinity maturation and differentiation
74
what is the T cell rich area in the lymph node?
paracortex
75
what do naive lymphocytes enter the lymph nodes through?
high endothelial venules (HEVs)
76
how do APCs use the lymph nodes?
- enter
| - scan for lymphocytes
77
what happens if an APC is recognised by a T cell?
multiplies and expands
| - helps the B cells
78
by what process are B and T cells separated in the lymph node?
- 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
how are B cells attracted in the lymph node?
- B cell areas rich in CXCL13
| - The ligand of CXCR5 on B cells
80
how are T cell attracted in the lymph node?
- 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
what is chemotaxis?
directed movement in response to chemicals
| - chemoattractant forms a gradient
82
what are chemokines?
chemotactic cytokines (secreted soluble proteins)
83
what is MALT?
- mucosa associated lymphoid tissues
| - large organised aggregates of lymphoid tissue in the digestive, respiratory and genitourinary tracts
84
what are Peyers patches?
- 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
