1
Q
What are the functions of the lymphatic system?
A
- Remove excess interstitial (tissue) fluid
- Immune defense
- Transportation of fats
2
Q
What is lymphoedema?
A
Localised fluid retention within the tissues causing tissue swelling –> obstruction –> high risk of infection
3
Q
How is lymph flow maintained?
A
- Contain valves
- Contraction of skeletal muscle and arteries
4
Q
Where is lymph carried?
A
In circulatory system
5
Q
What if the function of the thoracic duct?
A
- Drains lymph into left jugular vein or vena cava
- Collects lymph from left side of thorax and chyle cistern
- Largest duct
6
Q
Where does chyle cisterna collect lymph from?
A
-The cistern drains the abdomen, hind limbs and the pelvic regions.
7
Q
What is chyle?
A
- Lymph from the digestive system
- Contains CHYLOMICRONS (protein coated lipid droplets ) which drain into lymphatic capillaries in SI (lacteals)
8
Q
What is the function of lacteals?
A
Return chyle to chyle cistern
9
Q
What are the palpable lymph nodes in the dog?
A
-Submandibular, prescapular, popliteal, axillary (not always)
10
Q
What are the palpable lymph nodes in the cow?
A
-Submandibular, prescapular, subiliac, mammary (if infected)
11
Q
Describe the anatomy of the lymph node
A
- Medulla: contains macrophages and plasma cells
- Outer cortex (lymphatic follicle): follicles with B cells
- Deep cortex (paracortex): contains T cells (CD4 Th + CD8 cytotoxic)
- High endothelial venule: exit of lymphocytes into the blood
12
Q
What is the lymph circulation in the lymph node?
A
Afferent lymphatic vessel –> capsule –> subscapsular sinus –> paratrabecular sinus –> medulla –> medullary sinus efferent lymphatic vessel
13
Q
What is the cause of swollen lymph nodes?
A
- Infection
- Rapid cell turnover
- Inflammatory mediators
14
Q
What is metastasis?
A
As flow through LN’s are slow cells from primary tumours enter the lymphatic and grow as secondary tumoours in the LN’s
15
Q
What is the structure and function of the thymus?
A
- Primary lymphoid tissue: where lymphocytes are matured
- involved in positive and negative selection
- ruminants and pigs have 2 lobes: cervical and thoracic
- Cortex- contains T cells (where positive selection occurs )
- Medulla- contains macrophages (where negative selection occurs)
- Hassall’s corpuscles in the medulla
16
Q
What is the structure and function of the spleen?
A
- Secondary lymphoid tissue
- White pulp- contains lymphocytes
- PALS (in white pulp): contain Th cells
- Splenic follicles (in white pulp): contain Bcells and macrophages
- Red pulp- filters and removes old and damaged RBC’s
- Haematopoeisis
17
Q
What is the blood supply in the spleen?
A
Trabecular artery –> white pulp- central a. –> marginal sinus –> drain into red pulp vascular spaces –> splenic venules + veins –> hepatic portal vein –> liver
18
Q
What is a primary lymphoid organ?
A
- involved in maturation of lymphocytes
- Bone marrow, thymus, Bursa of Fabricus, Peyer’s Patch, appendix (in rabbits)
19
Q
What is a secondary lymphoid organ?
A
- Where lymphocytes are activated + proliferated
- Spleen, LN’s, MALT
20
Q
What is positive selection?
A
- Process where T cells are equipped with correct receptors to identify self molecules MHC
- within the cortex of thymus
21
Q
What is negative selection?
A
- Process where T cells that recognise MHC as non self are removed by macrophages
- In the medulla of thymus
22
Q
Where is the follicle associated epithelium present and what is it specialised for?
A
- in Peyer’s Patch
- specialised for antigen uptake
23
Q
What is the structure of lymph capillaries?
A
- lined by continuous single layered endothelium
- No valves
- Interstitual fluid enter via openings at intervals between adjacent endothelial cells
24
Q
What is the structure of lymph vessels?
A
- Thinner walls than normal vessels
- More valves than normal vessels
25
What is the structure of the collecting ducts?
- Receives chyle from intestine
- Receives lymph from head and neck
- Opens into vena cava and left jugular
26
What is haemosiderophages?
retrieval of iron from erythrocyte breakdown
27
What is a sinusoid?
Small irregular shaped blood vessel
28
What are the roles of cell communication?
-movement, coordination of metabolism, coordination of growht/development, coordination of immune response
29
What are the 3 modes of cell communication?
- Contact dependent - gap junctions
- Synapse
- Autocrine, paracrine, endocrine
30
What are the advantages of contact dependent- gap junctions?
- can communicate via cytoplasmic bridges
| - allows movement of ions, metabolites and complex molecules i.e. CAMP
31
What are the disadvantages of contact dependent- gap junctions?
- can only communicate with cells nearby
- relatively slow transmission
- transmission of deletion factors
32
What are the advantages of synaptic transmission?
- do not involve any changes in chemical concentrations
- communciation across short synaptic cleft- fast
- no dilutions
- system can be reactivated quickly
33
What are the disadvantages of synaptic transmission
- specificity
- hardwriting is expensive
- vulnerable
34
What is autocrine, paracrine and endocrine?
- autocrine: self signalling
- paracrine: cells nearby
- endocrine: cells distant
35
How does signalling come about?
Ligand binds to receptor on mebrane --> singal transduction --> effect
36
Where are the majority of cytokines formed and how do they cause a response?
- produced de novo
| - stimulation --> signal --> transcription and translation of protein (Cytokine) --> repsonse within hours
37
Where are the minority of cytokines produced and how do they cause a repsonse?
- stored as precursors and released upon stimulation
| - stimulation --> signal --> straight to precursor --> mature protein --> response within minutes
38
What are the functions of cytokines?
- immunity
- haematopoiesis
- embryogenesis
39
What are the nature of cytokines?
- Pleiotrophy of cytokines: a cytokine can have a different effect in different cells
- Redundancy of cytokines: 2 or more cytokines may have similar effects
- Synnergy of cytokines: combined effect of cytokines can be greater compared to just one
- Antagonism- one cytokines may inhibit the effect of another
- Cascade activation- 1 many induce a cascade of cytokine expression involving multiple cells
40
What are the different domains of cytokine receptors?
- Binding site
- Transmembrane domain
- signal domain : activates enzyme activity
41
What are the different types of receptors/domains?
- Single receptor with signal domain
- Receptor with accessory protein complex
- Receptor multioner complex
42
What are the different cytokine receptor families?
- immunoglobulin super family receptors
- chemokine receptors
- TNF receptors
- class I cytokine receptors
- class II cytokine receptors
43
Define neoplasia
Presence/formation of new, abnormal growth of tissue
44
Define tumour
Swelling part of body genereally without inflammation caused by abnormal growth (benign or malignant)
45
Define mutagenesis
Process by which genetic information of an organism is changed resulting in a mutation
46
Define oncogenesis
A gene which in certain circumstances can transform a cell into a tumour cell
47
What is a benign tumour?
- not cancerous
- can be removed
- does not spread to other parts of the body
48
What is a malignant tumour?
- cancerous
- spread to other tissues
- usually grow faster
49
Define angiogenesis
Development of new blood vessels
50
Define metastasis
When cells move away from primary site and spread to other organs where they continue to grow and form another tumour at that site.
51
Why does metastasis require angiogenesis?
As tumour cells get bigger and divide they become futher away from blood vessels and therefore send out angiogenic factors that cause a new blood supply
-supplies tumour with oxygen and nutrients
52
Describe the step-by-step process by which metastasis occurs
1) formation of primary tumour
2) separation + invasion of tumour into blood vessels causing a haematogenous spread/lymphahatic system
3) reaching of new organ
4) formation of secondary tumour
53
Define necrosis
Accidental cell death/ lethal cell injury
54
How do cells become necrotic?
Organism has a failure of membrane integrity --> membrane becomes permeable --> membrane swell --> inflammatory response kills cell
55
Define pyknosis
condesation and reduction in size of cell nucleus
56
Define karyorrhexis
Nuclear fragmentation with scattering of pieces in cytoplasm
57
Define apoptosis
Programmed cell death
58
What does an increased apoptosis cause?
Cell loss/atrophy
59
What does a reduced apoptosis cause?
Cell accumulation (neoplasia)
60
What is apoptosis used for?
- limb development: cell death between digits
- ossification: death of chondrocytes
- nervous system: death of neurons
61
What are the 3 stages of apoptosis and what occurs within each stage?
```
EARLY
-decreased cell size = cell dehydration
-altered cell membrane function
-large DNA strand breaks
- increase in cellular calcium levels
INTERMEDIATE
-DNA cleavage into 180-200bp fragments
-further decrease in cell size
-decreased pH
LATE
-loss of membrane function
-formation of apoptopic bodies
-phagocytosis- without inflammation
```
62
Describe benign and malignant tumours in terms of histology
- Benign have normal gland tubules, neoplastic gland tubules, enclosed in fibrous CT capsule
- Malignant have fewer normal gland tubules, invasive cancerous gland tubules
63
What is acute inflammation?
- Most common
- Lasts days (most weeks)
- Repairs damage/remove infection + stimulus
64
What is chronic inflammation
- occurs with persistent infection
- wound may not heal because of foreign body continuing infection
- may also occur where no obvious foreign body present
65
State what occurs during acute inflammation
1) bacteria/fungi damaged epithelium
2) causing cytokine production/stimulates other resistant cells
3) neutrophils go to site, mast cells + histamine (+any other vasoactive substance that increases vascular premeability)[migrate out of blood vessel]
66
What is the function of IL-1B
- Activates vascular endothelium
- local tissue distruction
- stimulates IL-6
67
What is the function of TNFa
- Activates vascular endothelium
- Increase IGls entry
- complement +fluid drainage of lymph
68
What is the function of IL-6
- Lymphocyte activation
| - Increase antibody production
69
What is the function of IL-8
-Attracts neutrophils, basophils, T cells to site
70
What is the function of IL-12
-Activates NK cells, induces differentiation of CD4 T cells into Th cells
71
What are the functions of mast cells and what do they release?
- release granules into interstitium
| - release prostaglandin D2 (PGI2), leukotrine C4, cytokines
72
What are the functions of histamine?
- Dilation of blood vessels
- Increases permeability of vessels- makes them more leaky
- Activates endothelium
73
Explain tethering and rolling
1) Local endothelial cells express integrin receptors
2) leucocytes will also express these inegrin receptors
3) binding of integrin receptors slows down leucocytes near infected area
4) Reorganisation of cytoskeleton of leucocytes
5) changes cell shape = spread over endothelium = DIAPEDESIS
74
What is diapedesis?
When leucocytes pass between gaps in endothelium
75
What are plasma proteins?
Produced in the liver in response to cytokines secreted during inflammation
- C-reactive protein and fibrinogen --> in response to IL-6
- Serum amyloid A protein --> in responnse to IL-1 and TNFa
76
What is used for diagnosis of systemic inflammation?
- Erythrocyte sedimentation rate (indirect): by increase in fibrinogen --> erythrocytes forms stacks
- Canine C reactive protein: enhances phagocytosis by macrophages
77
What is a granuloma?
If anti-inflammaotry cytokines are not produced you get chronic inflammation which causes a granuloma
- aggregates of chronically stimulated infllamtory cells
- prevents spread of antigen
78
What is a collection of modified macrophages called?
Epitheloid cells + surrounding zone of lymphocytes
79
What is a langhans cell
- Giant cell
| - fusion of macrophages
80
What can happen to a granuoloma
- Can become caseous + fibrotic = calcifies
81
What is the indirect method of ELISA?
Antigen immobilized on solid support via absorption to surface
-detects ANTIBODY
82
What is the process of ELISA (direct)?
1) Well coated with capture antibody
2) Addition of sample/antigen
3) Addition of primary antibody = sandwich formation
4) Addition of secondary antibody= conjugated to substrate specific enzyme
5) Substrate added and converted enzyme = colour change
83
What are the uses of ELISA?
-disease detection, illegal drugs, hormones
84
Why is the blocking agent added to ELISA?
To ensure nothing sticks to the well
85
What is the purpose of washing after every step in ELISA?
Removes unbound antigens/bodies
86
What are the cellular components of blood?
- Erythrocytes
- Leucocytes (granular + non granular)
- Platelets
87
List some granular leucocytes
-neutrophils, basophils, eosinophils
88
What are platelets generated from?
Megakaryocyte
89
What are macrophages generated from?
Monocytes
90
What are lymphocytes generated from?
CLP (common lyohoid pregenitor cell)
91
What is haematopoiesis
Generation of blood leucocytes within bone marrow
92
Explain the generation and maturation of a T cell within bone marrow
Common lymphoid pregenitor cell --> pre T cell --> (IL-2, IL-7- growth factors) --> mature T cell
-same process occurs with B cells into mature B cells/plasma cells
93
What are the 3 stains used to identify leucocytes
- GIEMSA: cytoplasms shade of pink, used in blood smears
- WRIGHT: bone marrow aspirates + blood smears
- LEISHMAN: blood smears, distinguishes protozona parasites
94
What is the development and function of neutrophils?
- Development: GM-CSF (granulocyte-macrophage colony stimulating factor) + IL-3 + Granulocyte CSF
- Function: chemotaxis, phagocytosis and killing
- O2 dependent/ independent
95
How do neutrophils kill in absence of oxygen?
- Neutrophils that do not need oxygen to break down bacteria
| - Lysozymes hydrolyses glycoppeptide coat of bacteria
96
How do neutrophils kill in presence of oxygen?
- Generation of reactive O2 species i.e. H2O2, H reduced (superascide anion) --> damage bacterial membranes
- production of hyperchloric acid
97
What does pus consist of?
Dying neutrophils
98
What can you see in a mature neutrophil?
Segmented nucleus
99
What are the functions of eosinophils?
- Have granules are released in response to allergic, parasitic + fibrosis
- Can be weakly phagocytic
- Surface IgE receptors
100
What are the functions of mast cells
- Same as eosinophils but present in connective tissue
| - granules release histamine, heparin, proteases, leukotrines, ILs, PGI2
101
What are the functions of mast cells?
-Found within blood not tissue: in tissues become macrophages/denetric cells
102
What is the function of a dendritic cell?
Communicate with T cells
103
What are the 3 models of immune response?
- Burnett + Medawar: self vs non self
- Janeway: infectious non self
- Mattzinger: danger model
104
What is central tolerance?
- Thymic education
| - Process where lymphocytes are tested to see if they react to self antigen - must be prevented
105
What is involution in regards to lymphoid tissue?
After birth lymphoid tissue becomes replaced by adipose and connective tissue
106
Explain process of T cell maturation
1) Prothymocyte (immature T cell) develop from BM
2) Migrate to thymus where self recognising T cells are removed via negative selection
3) Mature T cells leave thymus with CD4+ / CD8+
107
What is a cytotoxic T lymphocyte?
- CD8+ / CD4-
- MHC I restricted
- Kill virus infected cells which express MHC I
108
What is a helper T lymphocyte?
- CD4+ / CD8-
- MHC II restricted
- Interact with APCs + produce cytokines which activate innate cells
- Stimulate antibody production
109
What occurs during positive selection?
- Selects T cells which interact with MHC
- Thymocyte TCR interacts with MHC on epithelial surfaces
- If positive you get development otherwise you get apoptosis
110
What occurs during negative selection?
- Single +ve lymphocytes in medulla are tested to see if they react with MHC
- TCR interacts with MHC + self peptide on DC/macrophage
- If negative reaction = development otherwise apoptosis
111
What are the regions in a TCR?
- Varibale region: where antigen binding occurs
| - Constant region: involved in signalling
112
What is the B cell receptor composed off?
IgM
113
What is receptor editing?
In high proportion of self reacting cells the BCR genes are rearranged to prevent reaction rather than cell death which only occurs in B cells
114
What is an epitope?
Specific surface receptors acquired by lymphocytes during maturation
115
What is the naive lymphocyte circulation through LNs?
1) Bind to high endothelial venules
2) B cells to cortex and T cells to paracortex (in blood vessels)
3) Exit via efferent lymphatic vessel
4) through to thoracic duct and vena cava/left jugular
116
What is the memory lymphocyte circulation through LNs?
1) Pass into LN via blood/endothelium/tissue/afferent lymphatic vessel
2) B cells to cortex and T cells to paracortex
3) efferent lymphatic vessel --> TD --> blood
117
What is used to help lymphocytes be directed to specific areas?
- chemokines direct Lo to correct areas of node
- homing receptors direct Lo to appropriate organs
- HEVs faciliate entry to naive Lo
118
What 2 mechanisms can occur if a naive T cell encounters an antigen?
- can become long lived memory cells
| - become effector cells and are short lived therefore die by apoptosis
119
Outline the adaptive immune response
1) capture antigen via APC-phagocytosis
2) process via MHC + transport to L/N
3) present to B cells and T cells
4) adaptive response/ clonal selection / memory cells
120
What is the role of a B cell?
Differentiate into plasma cells and secrete Ig antibodies
121
What is the role of a T cell?
Become CD4+ /CD8+ and lyse cells directly
122
What is unique about BCR?
- Can capture antigen directly
- can undergo class switching via gene rearrangement (constant region chains)
- can undergo somatic mutations during Lo development
