39. Immunopathology Flashcards
(166 cards)
1
Q
A
2
Q
Define Rheumatoid Arthritis.
A
Chronic autoimmune disease characterised by pain, stiffness and symmetrical synovitis of synovial joints
3
Q
What is the site of inflammation in rheumatoid arthritis?
A
Synovium
4
Q
What are the two main autoantibodies that are associated with rheumatoid arthritis?
A
Rheumatoid factor Anti-cyclic citrullinated peptide antibody
5
Q
Other than at joints, where else is synovium found?
A
Around tendons (tenosynovium)
6
Q
Define Ankylosing Spondylitis.
A
Chronic spinal inflammation that can result in fusion and deformity
7
Q
What is the site of inflammation in ankylosing spondylitis?
A
Entheses – where a ligament or a tendon inserts into bone
8
Q
What family of diseases is ankylosing spondylitis a part of?
A
Seronegative spondyloarthropathies
9
Q
Which other diseases fall into this family of diseases?
A
Reiter’s syndrome and reactive arthritis Psoriatic arthritis Enteropathic synovitis
10
Q
Define Systemic Lupus Erythematosus (SLE).
A
Chronic tissue inflammation in the presence of antibodies directed at self-antigens NOTE: it is inflammation of sterile tissue
11
Q
Lupus causes multi-site inflammation but state some sites that are particularly badly affected.
A
Joints, Skin and Kidneys
12
Q
What are the two autoantibodies that are associated with lupus?
A
Anti-nuclear antibodies Anti-double stranded DNA antibodies
13
Q
What family of diseases is lupus a part of?
A
Connective tissue diseases
14
Q
What other diseases are part of this family?
A
Systemic sclerosis (diffuse and localised) Polymyositis/Dermatomyositis Sjogren’s syndrome Mixed connective tissue disease
15
Q
What is Sjogren’s syndrome?
A
An autoimmune disease that targets the exocrine glands (e.g. lacrimal glands)
16
Q
What are the MHC associations of rheumatoid arthritis, ankylosing spondylitis and SLE?
A
Rheumatoid arthritis – HLA-DR4 SLE –HLA-DR3 Ankylosing spondylitis – HLA-B27
17
Q
On which chromosome is HLA encoded?
A
Chromosome 6
18
Q
A change in which class of MHC is associated with rheumatoid arthritis, ankylosing spondylitis and SLE?
A
Ankylosing spondylitis = Class 1 Rheumatoid Arthritis + SLE = Class 2
19
Q
Which cells express class I MHC and which cells recognise this class of MHC?
A
All nucleated cells (they display endogenous antigens) They are recognised by CD8+ T cells
20
Q
Which cells express class II MHC and which cells recognise this class of MHC?
A
Antigen presenting cells e.g. macrophages, dendritic cells (they display exogenous antigens) Recognised by CD4+ T cells
21
Q
How does HLA-B27 cause ankylosing spondylitis?
A
Ankylosing spondylitis is independent of CD8+ T cells HLA-B27 has a propensity to misfold, which causes cellular stress and triggers the release of IL-23 and IL-17 by adaptive immune cells and innate immune cells The release of chemical mediators leads to inflammation The cellular stress is most likely to occur in innate immune cells and these are present in the entheses – hence why ankylosing spondylitis causes enthesitis
22
Q
What is the key autoantibody in: a. Diffuse systemic sclerosis b. Limited systemic sclerosis c. Dermatomyositis/Polymyositis d. Mixed connective tissue damage
A
a. Diffuse systemic sclerosis Anti-Scl-70 antibody b. Limited systemic sclerosis Anti-centromere antibody c. Dermatomyositis/Polymyositis Anti-tRNA transferase antibody d. Mixed connective tissue disease Anti-U1-RNP antibody
23
Q
What is the difference in the specificity of the autoantibodies in SLE?
A
Anti-nuclear antibodies are found in all cases of SLE but isn’t specific to SLE Anti-dsDNA antibodies are specific to SLE – serum level of this antibody correlates with disease activity
24
Q
How is the presence of anti-nuclear antibodies detected?
A
Some cells are permeabilised so the antibodies can enter the cell andthen the patient’s serum is washed over the cells If there are anti-nuclear antibodies, they will bind to the nuclearantigens
25
What are the features of a sick lupus patient in terms of complement levels and serum levels of anti-dsDNA antibodies?
Low complement levels High serum levels of anti-dsDNA antibodies
26
How do antinuclear antibodies react with nuclear antigens, which are found within the nucleus?
Apoptosis leads to the translocation of nuclear antigens onto the surface of the cell so that they are accessible to the immune system In lupus, apoptotic cells are not cleared normally This impaired clearance enables abnormal presentation to the immune system The immune response is amplified through B cells
27
State some important cytokines in rheumatology.
IL-1 – produced by macrophages and activates T cells, fever + pro-inflammatory IL-2 – produced by T cells – activates T + B cells IL-6 – produced by T cells – activates B cells + acute phase response TNF-alpha – produced by macrophages – similar to IL-1 but more destructive Gamma-IFN – produced by T cells – activates macrophages
28
Blockage of which cytokine with biological therapy has proven to be very effective in reducing some of the negative effects of rheumatoid arthritis?
TNF-alpha
29
Other than cytokine blockade, what else can be targeted to improve symptoms in rheumatoid arthritis?
B cell depletion (B cell hyperactivity is a key feature of SLE)
30
What is RANKL produced by and what does it do?
RANKL is produced by T cells and synovial fibroblasts It stimulates osteoclast formation
31
What can upregulate RANKL production?
IL-17 IL-1 TNF-alpha PTH-related peptide
32
What decoy receptor antagonises the action of RANKL?
Osteoprotegrin
33
Name a monoclonal antibody that targets RANKL.
Denusomab
34
State two drugs that deplete B cells and specify what they target.
Rituximab – anti-CD20 monoclonal antibody Belimumab – anti-BLYS monoclonal antibody (BLYS is a B cell survival factor)
35
What are the effects of prostaglandins produced by COX?
Vasodilation, inhibit platelet aggregation, bronchodilation, uterine contraction
36
What are the effects of leukotrienes produced by lipooxygenase?
Leukocyte chemotaxis, smooth muscle contraction, bronchoconstriction, mucous secretion
37
What do glucocorticoids inhibit?
Phospholipase A2
38
What diseases come under the category of ‘connective tissue disease’?
SLE Systemic sclerosis Dermatomyositis/polymyositis Sjogren’s syndrome Mixed connective tissue disease
39
Which gender does SLE more commonly affect?
Females 9:1
40
Describe the presentation of SLE including some specific features.
Malaise, fatigue, weight loss, fever, lymphadenopathy Specific features: Butterfly rash Alopecia Arthralgia Long history of Raynaud’s phenomenon
41
Describe the characteristics of the rash seen in SLE.
It tends to go across the nose It may look a bit like acne It is not painful or itchy Some rashes become depigmented when the inflammation spreads to the dermis (depigmentation and scarring is irreversible)
42
Describe the pathogenesis of SLE.
SLE patients have a defect in apoptosis Apoptotic cells are not cleared properly so they persist and expose their nuclear antigens and autoantibodies are generated against these nuclear antigens The defect in apoptosis is combined with B cell hyperactivity The overactive B cells are exposed to the nuclear antigens and the plasma cells begin to produce autoantibodies that circulate and form immune complexes The immune complexes deposit in tissues and activate complement leading to inflammation
43
What is the first investigation performed in the diagnosis of SLE?
Check for anti-nuclear antibodies (this is not specific for SLE though)
44
The pattern with which the antinuclear antibodies bind to the nuclear antigens is important in reaching a diagnosis. List some different patterns and the antigens they are associated with.
Homogenous – DNA Speckled – antibodies to Ro, La, Sm and RNP Nucleolar – topoisomerase – scleroderma Centromere – limited cutaneous scleroderma
45
What conditions are associated with the presence of anti-Ro and anti-La antibodies?
Neonatal lupus syndrome Subacute cutaneous lupus erythematosus
46
What are some other tests that can be done for SLE?
Measuring complement levels Anti-cardiolipin antibodies Lupus anticoagulant Beta 1 glycoprotein
47
Describe the haematological features of SLE.
SLE is generally associated with low blood counts Thrombocytopenia Lymphopenia Normocytic anaemia Autoimmune haemolytic anaemia
48
What renal changes might occur in SLE?
Proteinuria Haematuria Active urinary sediment
49
List some clinical features that could help pre-empt severe attacks in SLE.
Malaise, weight loss, alopecia, rash
50
List some laboratory markers that could help pre-empt severe attacks in SLE.
Raised ESR Raised anti-dsDNA antibodies Reduced complement levels
51
Describe the differences between mild, moderate and severe disease in SLE.
Mild – skin and joint involvement Moderate – inflammation of other organs (e.g. pleuritis, pericarditis) Severe – severe inflammation of vital organs
52
Describe the treatment of mild disease.
Paracetamol and NSAIDs Hydroxychloroquine (good for arthropathy and cutaneous manifestations) Topical corticosteroids
53
Describe the treatment of moderate disease.
ORAL GLUCORTICOIDS Start with a HIGH dose and titre downwards
54
Describe the treatment of severe disease.
Azathioprine – useful steroid-sparing drug Has a risk of neutropenia/bone marrow suppression so needs regular blood monitoring Cyclophosphamide – one used if there is severe organ involvement Problem – infertility
55
Name and explain the mechanism of action of two new treatments for severe disease.
Mycophenolate mofetil Reversible inhibitor of inosine monophosphate dehydrogenase This is the rate limiting step in de novo purine synthesis Lymphocytes rely heavily on de novopurine synthesisRituximab Anti-CD20 antibody Causes depletion of B cells Useful in lupus nephritis
56
SLE has and early peak and a late peak in mortality. What are the usual causes of the two peaks?
Early – renal failure, CNS disease, infection Late – MI and stroke
57
What can usually be seen on the blood film of a patient with SLE?
Schistocytes (evidence of microangiopathic haemolytic anaemia) Teardrop cells Spherocytes Few leukocytes Few platelets
58
Describe the appearance of a renal biopsy in a patient with SLE
Hypercellular Mesangial proliferation Crescent development
59
Which gender does SLE more commonly affect?
Females 9:1
60
Describe the presentation of SLE including some specific features.
Malaise, fatigue, weight loss, fever, lymphadenopathy Specific features: Butterfly rash Alopecia Arthralgia Long history of Raynaud’s phenomenon
61
Describe the characteristics of the rash seen in SLE.
It tends to go across the nose It may look a bit like acne It is not painful or itchy Some rashes become depigmented when the inflammation spreads to the dermis (depigmentation and scarring is irreversible)
62
Describe the pathogenesis of SLE.
SLE patients have a defect in apoptosis Apoptotic cells are not cleared properly so they persist and expose their nuclear antigens and autoantibodies are generated against these nuclear antigens The defect in apoptosis is combined with B cell hyperactivity The overactive B cells are exposed to the nuclear antigens and the plasma cells begin to produce autoantibodies that circulate and form immune complexes The immune complexes deposit in tissues and activate complement leading to inflammation
63
Describe the appearance of a renal biopsy in a patient with SLE
Hypercellular Mesangial proliferation Crescent development
64
What can usually be seen on the blood film of a patient with SLE?
Schistocytes (evidence of microangiopathic haemolytic anaemia) Teardrop cells Spherocytes Few leukocytes Few platelets
65
SLE has and early peak and a late peak in mortality. What are the usual causes of the two peaks?
Early – renal failure, CNS disease, infection Late – MI and stroke
66
Name and explain the mechanism of action of two new treatments for severe disease.
Mycophenolate mofetil Reversible inhibitor of inosine monophosphate dehydrogenase This is the rate limiting step in de novo purine synthesis Lymphocytes rely heavily on de novopurine synthesisRituximab Anti-CD20 antibody Causes depletion of B cells Useful in lupus nephritis
67
Describe the treatment of severe disease.
Azathioprine – useful steroid-sparing drug Has a risk of neutropenia/bone marrow suppression so needs regular blood monitoring Cyclophosphamide – one used if there is severe organ involvement Problem – infertility
68
Describe the treatment of moderate disease.
ORAL GLUCORTICOIDS Start with a HIGH dose and titre downwards
69
Describe the treatment of mild disease.
Paracetamol and NSAIDs Hydroxychloroquine (good for arthropathy and cutaneous manifestations) Topical corticosteroids
70
Describe the differences between mild, moderate and severe disease in SLE.
Mild – skin and joint involvement Moderate – inflammation of other organs (e.g. pleuritis, pericarditis) Severe – severe inflammation of vital organs
71
List some laboratory markers that could help pre-empt severe attacks in SLE.
Raised ESR Raised anti-dsDNA antibodies Reduced complement levels
72
List some clinical features that could help pre-empt severe attacks in SLE.
Malaise, weight loss, alopecia, rash
73
What renal changes might occur in SLE?
Proteinuria Haematuria Active urinary sediment
74
Describe the haematological features of SLE.
SLE is generally associated with low blood counts Thrombocytopenia Lymphopenia Normocytic anaemia Autoimmune haemolytic anaemia
75
What are some other tests that can be done for SLE?
Measuring complement levels Anti-cardiolipin antibodies Lupus anticoagulant Beta 1 glycoprotein
76
What conditions are associated with the presence of anti-Ro and anti-La antibodies?
Neonatal lupus syndrome Subacute cutaneous lupus erythematosus
77
The pattern with which the antinuclear antibodies bind to the nuclear antigens is important in reaching a diagnosis. List some different patterns and the antigens they are associated with.
Homogenous – DNA Speckled – antibodies to Ro, La, Sm and RNP Nucleolar – topoisomerase – scleroderma Centromere – limited cutaneous scleroderma
78
What is the first investigation performed in the diagnosis of SLE?
Check for anti-nuclear antibodies (this is not specific for SLE though)
79
What diseases come under the category of ‘connective tissue disease’?
SLE Systemic sclerosis Dermatomyositis/polymyositis Sjogren’s syndrome Mixed connective tissue disease
80
What are hypersensitivity reactions usually mounted against?
Harmless foreign antigens Autoantigens Alloantigens
81
What are the four type of hypersensitivity reaction?
Type 1 – immediate hypersensitivity Type 2 – antibody-mediated cytotoxicity Type 3 – immune complex mediated Type 4 – delayed cell mediated
82
Describe the mechanism of type 1 hypersensitivity?
On 1st exposure you get sensitisation – IgE is produced, which binds to mast cells and basophils On subsequent exposure, antigen cross-links the IgE on the mast cells causing degranulation and release of inflammatory mediators
83
What types of diseases are examples of type 2 hypersensitivity?
Organ specific autoimmune diseases: e.g. myasthenia gravis, glomerulonephritis, pemphigus vulgaris, pernicious anaemia Autoimmune cytopenias e.g. autoimmune haemolytic anaemia, thrombocytopenia, neutropenia
84
What are the consequences of immune complex formation in type 3 hypersensitivity?
Immune complexes deposit in tissues and activate complement and cause cell recruitment This can cause tissue damage
85
Give some examples of diseases caused by delayed type hypersensitivity.
Chronic graft rejections Graft-versus-host disease Coeliac disease
86
Describe the mechanism of delayed type hypersensitivity.
The transient/persistent antigen is presented to T cells, which then activate macrophages and CTLs Activated macrophages produce TNF-alpha, which is responsible for much of the tissue damage
87
What are three important cytokines released by Th2?
IL-4 IL-5 IL-13
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What is the difference between the antigens involved in type 2 and type 3 hypersensitivity?
Type 2 – insoluble antigens (cell surface or matrix bound antigens) Type 3 – soluble antigens
89
What is atopy?
A form of allergy in which there is a hereditary or constitutional tendency to develop hypersensitivity reactions in response to allergens
90
How common is atopy?
Very common – about 50% of young adults in the UK
91
List some genetic risk factors of atopy.
About 80% of atopics have a family history The genetic component is polygenic but genes of the IL-4 cluster and genes on chromosome 11q have been linked to atopy
92
Among which age group is atopy most common?
Teens
93
Describe the gender difference in asthma
Males – asthma in childhood is more common Females – asthma in adulthood is more common
94
What other environmental factors affect atopy?
Family size, infections, animals, diet
95
What type of hypersensitivity is responsible for anaphylaxis, urticaria and angioedema?
Type 1 hypersensitivity
96
What type of hypersensitivity is responsible for chronic urticaria?
Type 2 hypersensitivity
97
What type of hypersensitivity is responsible for asthma, rhinitisand eczema?
Type 1 and type 4 hypersensitivity
98
Describe sensitisation in atopic airway disease.
T cells are naïve before they have seen their antigen Once the T cells are exposed to the antigen by APCs, they can become Th1 cells (producing IFN-gamma), T regs or Th2 cells Th2 cells lead to the activation of B cells and the production of IgE antibodies
99
Describe what happens in second exposure to the allergen.
In second exposure, the allergens are presented by APCs to memory Th2 cells, which then release IL-5, which causes eosinophil degranulation Th2 cells also release IL-4 and IL-13, which stimulate production of IgE by plasma cells The antigens crosslink the IgE on the surface of mast cells causing degranulation
100
What percentage of blood leukocytes are eosinophils?
2-5%
101
Describe the appearance of the nucleus of eosinophils.
Bilobed
102
What receptors do mast cells have on their cell surface?
IgE receptors
103
What mediators are released by mast cells?
Preformed: histamines, cytokines, toxic proteins Newly synthesised: leukotrienes, prostaglandins
104
What percentage of blood leukocytes are neutrophils?
55-60%
105
What three processes cause airway narrowing in an acute asthma attack?
Vascular leakage leading to airways wall oedema Mucus secretion fills up the lumen Smooth muscle contraction around the bronch
106
Describe the changes seen in a patient with chronic asthma.
The lumen of the airway is narrowed and the airway wall is grossly thickened There will be cellular infiltration by Th2 lymphocytes and eosinophils There will be smooth muscle hypertrophy, mucus plugging, epithelial shedding and subepithelial fibrosis
107
State some important clinical features of asthma.
Chronic episodic wheeze Bronchial hyperresponsiveness Cough Mucus production Breathlessness Reduced and variable peak expiratory flow (PEF)
108
What can allergic eczema lead to sensitisation of?
House dust mites – their proteins can get through dry, cracked skin
109
What type of hypersensitivity is food allergy?
Type 1 hypersensitivity (IgE)
110
What are the symptoms of a mild reaction to a food allergy?
Itchy lips and mouth Angioedema Urticaria
111
What are the symptoms of a severe reaction to a food allergy?
Nausea Abdominal pain Diarrhoea Anaphylaxis
112
What is anaphylaxis?
Severe generalised allergic reaction
113
What is anaphylaxis caused by?
Generalised degranulation of IgE sensitised mast cells
114
State some symptoms of anaphylaxis.
Itchiness around mouth, pharynx and lips Swelling of the lips and throat Wheeze, chest tightness, dyspnoea Faintness, collapse Diarrhoea and vomiting
115
How can you test for allergies?
Skin prick test
116
What is the emergency treatment of anaphylaxis?
Adrenaline
117
Describe the step-by-step treatment of asthma.
Step 1: short acting beta 2 agonist (e.g. salbutamol) Step 2: low-moderate dose inhaled steroids (e.g. beclomethasone, budesonide, fluticasone) Step 3: add long acting beta 2 agonist or a leukotriene receptorantagonist + high dose inhaled corticosteroids Step 4: add courses of oral steroids
118
What are the two types of immunotherapy that are used to develop tolerance in patients?
Subcutaneous immunotherapy (SCIT) Sublingual immunotherapy (SLIT)
119
How much blood and how frequently can one donor give?
1 unit (1 pint) every 4 months
120
What glycoprotein and fructose stem is common to everyone?
H stem
121
What are A and B antigens?
The A and B antigens are made by the addition of a sugar residue onto the common glycoprotein and fructose stem (H stem)
122
What does the A gene encode?
An ENZYME that adds N-acetyl galactosamine to the H stem
123
What does the B gene encode?
An ENZYME that adds galactose to the H stem
124
Describe the inheritance pattern of the ABO blood groups.
A and B genes are codominant O is ‘recessive’ because it doesn’t code for anything at all So you need to be homozygous for O (OO) to be in blood group O
125
Which antibodies would someone in blood group A possess? Why?
Anti-B antibodies because each person produces antibodies against any antigen that is NOT present on their own red cells.
126
What class of immunoglobulin are these antibodies?
IgM They are naturally occurring (nearly from birth)
127
What would happen if someone with anti-B antibodies was given B-positive blood?
The anti-A/anti-B antibodies are complete antibodies meaning that it fully activates the complement cascade to cause haemolysis of red cells This is often FATAL It can lead to cytokine storm, lysis, cardiovascular collapse and death
128
In the laboratory, what would you see if you were to mix the plasma of someone of blood group A with the red cells of someone in blood group B?
Agglutination
129
What are the two most common blood groups in the UK?
A (42%) and O (47%)
130
What is done before transfusion to check that the donor blood and the recipient’s blood is compatible?
A blood sample is taken from the patient and the ABO blood group is determined (test with anti-A and anti-B antibodies) Select a donor unit of the same group CROSS-MATCH: patient’s serum is mixed with donor red cells – it should NOT react (if it reacts then it shows that it is incompatible)
131
Which rhesus antigen is the most important?
RhD
132
Describe the inheritance pattern of the RhD antigen.
Autosomal Dominant RhD codes for the D antigen
133
Describe the relative proportions of RhD positive and RhD negative individuals within the population.
RhD positive = 85% RhD negative = 15%
134
What can happen when RhD negative people are exposed to RhD positive blood?
They become sensitised and can make anti-D antibodies
135
What type of antibody are anti-D antibodies?
IgG
136
What are the implications on future transfusions of an RhD negative individual who has been sensitised to RhD following exposure?
In the future they must be transfused with RhD negative blood or the anti-D antibodies, generated from first exposure, will react with the RhD positive blood This will cause a delayed haemolytic transfusion reaction resulting in anaemia, high bilirubin, jaundice etc.
137
What is haemolytic disease of the newborn?
If an RhD negative mother generates anti-D antibodies following pregnancy with a RhD positive foetus, then if the next foetus is RhD positive, the mother’s anti-D antibodies (IgG) can cross the placenta and cause haemolysis of foetal red blood cells. If severe this can cause hydrops fetalis and death.
138
About 8% of transfused patients will form antibodies against antigens other than ABO and RhD. What are the implications of this?
Once they have formed antibodies against these other antigens, you must use corresponding antigen negative blood in future transfusions otherwise you risk a delayed haemolytic reaction.
139
What must you always do before transfusion in such patients?
Before each transfusion you should test the patient’s blood sample for red cell antibodies. So before transfusing a patient, as well as testing the ABO and RhD groups, you must do antibody screening of their plasma.
140
Why is whole blood no longer routinely given to patients?
It is inefficient Some components of the blood will degenerate quickly if it is stored as whole blood
141
Why are the red cells concentrated and the plasma removed?
It allows you to avoid fluid overloading, which can precipitate heart failure, when giving someone red cells
142
What three components is blood first separated into via centrifugation?
Plasma Platelets (and white cells) Red Cells
143
What is fresh frozen plasma (FFP) and what does it contain?
If the plasma is frozen within 6 hours of donation then all the coagulation factors are preserved – this is fresh frozen plasma (FFP)
144
How is cryoprecipitate produced and what does it contain?
Thawing FFP in a 4 degrees centigrade fridge over night produces Cryoprecipitate It contains: Fibrinogen Factor 8 Factor 13 Von Willebrand Factor Fibronectin
145
Explain what fractionation is and why it’s useful.
The plasma of many donors is pooled and put into a fractionating column. This means that various components such as albumin, haemophilia factors and anti-D antibodies can be pulled off. This is NOT done in the UK.
146
How many donors does it take to make one unit of red blood cells?
1
147
How are red blood cells stored and what is their shelf life?
They are packed cells with the plasma removed and they are stored in a 4-degree fridge Shelf-life = 5 weeks
148
How many donors does it take to make one unit of FFP?
1 (300 ml)
149
How is FFP stored and what is its shelf life?
It is stored at -30 degrees Shelf-life = 2 years
150
How is FFP thawed?
It is thawed at room temperature for 20-30 mins before use If thawed at too high a temperature you could cook the coagulation proteins You want to use it within half an hour of thawing because the coagulation factors could start to degenerate at room temperature
151
What is the normal dose of FFP?
12-15 ml/kg = 3 units
152
Why is it important to know the blood group of the patient before administering the FFP?
You need to know the blood group of the patient to make sure that theantibodies in the FFP don’t react with the recipient’s red blood cell antigens. If you give the wrong FFP it wont kill the patient because the antibodies are quite dilute but it will haemolyse some of the red cells which is not ideal.
153
What are the indications for FFP?
Bleeding and abnormal coagulation test results (PT and APTT) Reversal of warfarin (e.g. for urgent surgery) – this is because warfarin inhibits factor 2, 7, 9 and 10
154
How many donors does it take to make one standard dose of cryoprecipitate?
10 donors
155
What are the indications of cryoprecipitate?
If massive bleeding and fibrinogen is very low Rarely - hypofibrinogenaemia
156
How many donors does it take to make one standard adult dose of platelets?
4 donors
157
What machine can be used to get a standard dose from one donor?
Apheresis – cell separator machine
158
How are platelets stored and what is its shelf life?
They are stored at room temperature (22 degrees) and must be constantly agitated to prevent them from aggregating Shelf-life = 5 days (because of risk of bacterial infection)
159
Why is it important to give platelets of the same blood group to patients?
There is no need to X-match but you do need to give platelets of the same ABO blood groups because platelets have low levels of ABO. The wrong group of platelets would be destroyed quickly. Giving platelets of the wrong group could also cause RhD sensitization.
160
What are the indications for giving platelets?
Most haematology patients with bone marrow failure (platelets \<10 x 10^9/L) Massive bleeding DIC If very low platelets and the patient needs surgery If cardiac bypass needed and the patient is on anti-platelet therapy ONE POOL is usually enough
161
If a patient is bleeding post-surgery and his platelet count isnormal but he has a prolonged PT and APTT, which component(s) does he need?
FFP
162
If a patient is bleeding post-surgery and his PT and APTT are long and his fibrinogen is low, which component (s) does he need?
FFP and cryoprecipitate
163
State some commonly used fractionation products.
Factor 8 and 9 = used for haemophilia Factor 8 – also used for von Willebrand’s disease Immunoglobulins: IM: specific e.g. tetanus, anti-D and rabies IM: normal globulin – broad mix in the population
164
What can IVIg be used to treat?
Pre-op in patients with ITP (immune thrombocytopenic purpura – IVIg helps prevent the destruction of antibody coated platelets in the spleen and liver) and AIHA (autoimmune haemolytic anaemia)
165
What is albumin used to treat?
4.5% = useful in burns, plasma exchanges etc. 20% (salt poor) = for certain severe liver and kidney conditions only.
166
What measures are taken to ensure the safety of donated blood?
Exclude high-risk individuals Test for infections
