L5 and L6 The Blood Flashcards
1
Q
What is ‘haematocrit’?
A
The ratio of the volume of red blood cells to the total volume of blood
2
Q
Which two types of stem cell are involved in blood cell formation?
A
Myeloid stem cells (platelets, RBCs, monocytes, neutrophils, eosinophils, basophils)
Lymphoid stem cells (lymphocytes)
3
Q
Myeloid stem cells differentiate into what cell type?
A
Progenitor cells
4
Q
Lymphoid stem cells differentiate into what cell type?
A
Precursor cells
5
Q
True or false: Precursor cells cannot reproduce
A
False. Precursor cells develop into the formed elements of blood over several divisions.
Progenitor cells cannot reproduce, they are committed to forming their designated cell type (colony forming unit, CFU)
6
Q
Erythropoietin regulates the formation of which cell type(s)? Where is it released?
A
Red blood cells (erythrocytes)
Kidney
7
Q
Thrombopoietin regulates the formation of which cell type(s)? Where is it released?
A
Platelets (thrombocytes)
Liver
8
Q
Cytokines and interleukins regulate the formation of which cell type(s)?
A
White blood cells
9
Q
If a patient has kidney damage, production of which cell type may be reduced?
A
Red blood cells (erythrocytes), as erythropoietin is produced by the kidneys.
10
Q
If a patient has liver damage, production of which cell type may be reduced?
A
Platelets (thrombocytes), as thrombopoietin is produced by the liver.
11
Q
How are haemopoietic growth factors used in medicine?
A
Erythropoietin given to patients with kidney disease.
Various factors given after chemotherapy.
Thrombopoietin used to treat clotting disorders.
12
Q
How might kidney failure affect blood cell formation, what will the physiological effects of this be?
A
Reduced formation of erythrocytes, leading to less oxygen being carried, anaemia
13
Q
What will be the consequence of lowered TPO production?
A
Lower numbers of platelets, poor clotting
14
Q
What is the main difference between red and yellow bone marrow?
A
RBM is vascularised, full of pluripotent stem cells, produces blood cells. Yellow is avascular, full of fat.
15
Q
How does lymph differ from blood?
A
Lymph has no RBC, no globular proteins, and is in the lymphatic system, not the blood vessels
16
Q
What three gases can bind to red blood cells?
A
Oxygen
Carbon Dioxide
Nitric Oxide
17
Q
Which enzyme is present on red blood cells and involves the conversion of CO2 carbonic acid?
A
Carbonic Anhydrase
Produces carbonic acid (H2CO3) from CO2 and water.
Carbonic acid dissociates into bicarbonate ions (HCO3-) which are key in buffer control and CO2 transport.
18
Q
Damaged RBC’s are processed by which white blood cell?
A
Macrophages found in the spleen, liver or red bone marrow.
19
Q
Damaged RBC’s are phagoocytosed by macrophages (in spleen, liver, red bone marrow) where they are broken down into which components?
A
- Globin (further broken down into amino acids)
2. Heme (iron is removed and sent to liver, biliverdin is converted to bilirubin and sent to liver)
20
Q
Free iron is bad for the body. How is harm avoided during transport of iron?
A
Iron is bound to transferrin for transport in the plasma
21
Q
In what form is iron stored in the liver?
A
Ferritin
22
Q
After being formed from biliverdin, what is the journey taken by bilirubin?
A
It leaves the macrophage and is transferred to the liver, and then from the liver to the small intestine in bile.
In the small intestine, bacteria converts bilirubin to urobilinogen. Some of this is absorbed and transported to the kidneys where it is excreted in the urine (urobilin). The rest remains in the GI tract and is converted to stercobilin in the large intestine, which is excreted in faeces.
23
Q
Why is biliverdin converted into bilirubin?
A
Biliverdin is toxic, bilirubin is safe
24
Q
Iron stored in the kidney is transported to the bone marrow. What happens to iron in the bone marrow?
A
Combined with globin, vitamin B12 and erythropoietin as part of erythropoiesis - new RBC’s formed.
25
Which organs can be damaged by toxic iron overload?
Pituitary, adrenals, liver, testes, ovaries, pancreas, heart, thyroid and parathyroid
26
RBC production starts in the red bone marrow with the precursor cell type __?__
Pro-erythroblast
27
Which cell type divides several times to produce cell which make haemoglobin?
Pro-erythroblasts
28
__1__ eventually differentiate into __2__, which eject their nuclei.
1) Pro-erythrocytes
| 2) reticulocytes
29
What can be a consequence if erythropoiesis doesn't keep up with demand?
Hypoxia
30
What can cause underactivity of erythropoiesis?
Anaemia, dietary deficiencies, circulatory problems
31
What is injected to stimulate erythropoiesis?
Epoetin alfa (a form of human erythropoietin)
32
Why do many athletes train in places like Kenya?
High altitude = less oxygen = induced erythropoietin = more red blood cells = more oxygen-carrying capacity = better athlete
33
What is the Bohr effect?
Hydrogen ions (H+) reduce haemoglobin affinity for O2 by altering the haemoglobin structure so that it binds less easily with O2. When tissue pH is reduced (i.e. a rise in H+), O2 dissociates more rapidly from haemoglobin so that the O2 is unloaded to the tissues needing it.
34
What will the consequence of a lack of vitamin B12 be?
Erythroblasts require vitamin B12 for division and proliferation. Deficiency in B12 can lead to erythroblast apoptosis, causing anaemia due to ineffective erythropoiesis.
35
What effect will the accumulation of CO2 from metabolism have on the the ability of haemoglobin to carry oxygen?
[Bohr effect]
High levels of CO2 increases pH, altering haemoglobin so that it binds less easily with O2. As a result, the transported O2 is unloaded.
36
What effect will the accumulation of CO2 from metabolism have on the the ability of haemoglobin to carry oxygen?
[Bohr effect]
High levels of CO2 increases pH, altering haemoglobin so that it binds less easily with O2. As a result, the transported O2 is unloaded.
37
Which are the granular leukocytes?
Neutrophil, eosinophil, basophil
38
Which are the agranular leukocytes?
Lymphocytes, monocytes
39
Which of the leukocytes are non-specific?
Granular (neutrophil, eosinophil, basophil) and monocytes.
These are the 'first responders' that hold the fort until lymphocytes arrive.
40
How do eosinophil and basophil work together?
Basophil secrete heparin, histamine and serotonin as part of an allergic reaction. This opens the vessels to get as much fluid and lymphocytes to the site as possible.
Eosinophil release histaminase (histamine antagonist) to counteract and control the basophil response.
41
True or false, monocytes are macrophages that have left the blood and migrated into tissues.
False. It's the other way around
42
True or false: Mast cells are basophils which have migrated to tissue
True
43
Which leukocyte dilates blood vessels and induces inflammation through release of heparin and histamines?
Mast cell (basophil in tissue)
44
True or false: mast cells are involved in wound healing
True.
In addition to allergic reactions, mast cells are involved in wound healing and defense against pathogens.
45
Which leukocyte is a phagocytic cell that consumes foreign pathogens and cancer cells?
Macrophage (monocyte in tissue)
46
Which leukocyte differentiates into dendritic cells?
Monocytes
Also differentiate into macrophages
47
Which leukocyte is most abundant, representing 50-60% of all leukocytes?
Neutrophil
48
Which leukocyte releases toxins that kill or inhibit bacteria and fungi?
Neutrophil (and to some extent, eosinophil)
49
Which leukocyte is responsible for defence against parasites?
Basophil (and to some extent, eosinophil)
50
Which lymphocyte attacks bacteria and toxins?
B cells
51
Which lymphocyte attacks viruses?
T cells
52
Which lymphocyte attacks fungi?
T cells
53
Which lymphocyte attacks transplanted and cancerous cells?
T cells
54
What is Sialyl Lewis X? What function(s) does it have?
A carbohydrate molecule expressed on some cells.
1. Leukocyte 'tethering and rolling'. Leukocytes (such as neutrophil) slow themselves down in the blood stream by tethering to the Sialyl Lewis X receptors. They then roll along the endothelium while they decide whether or not to leave the blood.
2. Human fertilisation. Sialyl-Lewis X allows a sperm cell to recognize and fertilize an egg cell.
55
Which marker on a neutrophil allows it to tether to a Sialyl-Lewis-X receptor?
L-selectin
56
Binding to which receptor triggers migration of a leukocyte from the blood stream into the tissue?
E-selectin (in association with integrin)
57
What is diapedesis?
The passage of blood cells through the intact walls of the capillaries, typically accompanying inflammation.
58
What promotes the expression of Sialyl-Lewis-X?
Substances released by damaged tissue and bacteria
59
What is chemotaxis?
The directed migration of cells.
Neutrophil, for example, can detect a gradient of attractant, polarize, and migrate rapidly toward the highest concentration of the chemoattractant. Allows congregation of neutrophils at the site of infection.
60
A bacterial infection will result in high numbers of which leukocyte(s)?
Neutrophil
61
Stress will result in high numbers of which leukocyte(s)?
Neutrophil
62
Burns will result in high numbers of which leukocyte(s)?
Neutrophil
63
Inflammation will result in high numbers of which leukocyte(s)?
Neutrophil
64
What can cause low neutrophil count?
Radiation, systemic lupus erythematosus (SLE)
65
Viral infection will result in high numbers of which leukocyte(s)?
Lymphocytes, monocytes
66
Some leukaemias can result in high numbers of which leukocyte(s)?
Lymphocytes, basophils
67
Fungal infections will result in high numbers of which leukocyte(s)?
Monocyte
68
TB will result in high numbers of which leukocyte(s)?
Monocytes
69
Some chronic illnesses can result in high numbers of which leukocyte(s)?
Monocytes
70
What may cause a low lymphocyte count?
Prolonged illness, immunosupression
71
What may cause low monocyte count?
Bone marrow suppression
72
Allergic reactions will result in high numbers of which leukocyte(s)?
Eosinophils, basophils
73
Parasitic infections will result in high numbers of which leukocyte(s)?
Eosinophil
74
Leukaemias and cancers can result in high count of which leukocyte(s)?
Lymphocytes, basophils
75
What may cause a low eosinophil count?
Drug toxicity, stress
76
What may cause a low basophil count?
Pregnancy, ovulation, stress
77
What effect can stress have on leukocyte count?
Increased neutrophils; decreased eosinophils and basophils.
78
What is the importance of diapedesis, chemotaxis and phagocytosis for fighting bacterial infection?
Diapedesis: Allows neutrophil to leave bloodstream to enter affected tissue
Chemotaxis: Allows neutrophil to locate infection and move to it's location
Phagocytosis: Allows neutrophil to destroy bacteria causing infection
79
What is the cellular origin and development of platelets?
Haemopoietic stem cells differentiate into megakaryoblasts (in response to thrombopoietin), which produce megakaryocytes.
Megakaryocytes extend 'tendrils' into the bloodstream, from which platelets form.
80
How do platelets adhere to the vessel wall?
GPIb, GPIX, GPV receptors adhere to von Willebrand factor. vWf acts as an anchor-point on the vessel wall.
81
Red blood cells are biconcave disc-shaped cells lacking a nucleus, since this is extruded while the cell is maturing in the bone marrow.
What is the lifespan of red blood cells?
```
A) 28 days
B) 6 months
C) 4 days
D) 120 days
E) 14 days
```
D) 120 days
The diameter of a red cell is around 6.7–7.7 µm. The principal function of red cells is to carry oxygen and carbon dioxide round the body. The biconcave shape provides an increased surface area, compared with a sphere, making gas exchange faster, and is maintained by a complex cytoskeleton system. The adult red cell survives for about 120 days with a daily attrition rate of 2 × 1012 haemoglobin molecules per second.
82
Neutrophils are the most common leukocyte found in peripheral blood (50-70%) with a lifespan of around 8-10hrs.
How many lobes are contained in a neutrophil nucleus?
```
A) one
B) two to five
C) >10
D) none
E) eight
```
B) two to five
Characteristics of neutrophils:
* The nucleus contains between two and five lobes. Cytoplasmic granules contain proteolytic enzymes used to break down ingested material, e.g. pathogenic bacteria. The function of neutrophils is defence against bacteria and fungi.
* Neutrophils are attracted to sites of infection by chemoattractant chemicals to which they are very sensitive: bacterial cell wall proteins and endothelial cell molecules, such as leukotrienes.
* The various neutrophil granules contain several different proteins that fulfil the different functions of adhesion and bacterial killing; their release (neutrophil degranulation) is stimulated by leukotrienes and chemoattractants. The azurophilic granules contain enzymes that kill bacteria, such as lysozyme and myeloperoxidase, and others that facilitate the process, such as increasing membrane permeability.
83
Eosinophils are a type of leukocyte.
Which of the following is a function of eosinophils?
```
A) Defense against fungus
B) Defence against bacteria
C) Present antigens
D) Defence against helminth parasitic infestations
E) Serve as memory cells
```
D) Defence against helminth parasitic infestations
Eosinophils make up 1–6% total white cells in a healthy individual and have a striking orange appearance due to the cytoplasm that takes up eosin dye when blood films are stained. Eosinophils circulate in the peripheral blood for 4–5 h and then make their way to the tissues, where their main function is to provide defence against helminth (worm) parasitic infestations. Eosinophils also have a role in the control of allergies and fighting viral infections. Certain cytokines stimulate the increased production of these cells (eosinophilia).
84
Monocytes and macrophages are types of leukocytes.
What percentage of circulating white cells are represented by monocytes?
```
A) 50-70%
B) 25%
C) 5%
D) 20-40%
E) 0.2%
```
C) 5%
Monocytes are larger than neutrophils and make up around 5% of circulating white cells. The nucleus is characteristically kidney-shaped (indented), with vacuoles within the cytoplasm. Monocytes contain granules that store acid hydrolases and myeloperoxidase. Monocytes and macrophages can ingest pathogenic material; degrade it and present peptides or peptide fragments to T lymphocytes. Because of this function, monocytes and macrophages are called antigen-presenting cells, since they present antigen to T cells. Monocytes circulate for about 10 h in the blood before they mature into tissue macrophages. Their main role is to kill intracellular microorganisms, such as Listeria, mycobacteria and some fungi.
85
Platelets are fragments of megakaryocytes that bud off in bone marrow before entering the peripheral blood.
What is a characteristic of platelets?
```
A) Contain beta-granules
B) Contain chromosomes
C) Form a primary plug to plug small holes in damaged blood vessels to stop of slow bleeding
D) Nucleated
E) Survive for 120 days
```
C) Form a primary plug to plug small holes in damaged blood vessels to stop of slow bleeding
Platelets are non-nucleated. Megakaryocyte nuclei are large polyploid structures with chromosome contents between diploid (2N) and 64N, where N is a single set of chromosomes. The main role of platelets is to plug small holes in the blood vessel wall (primary haemostasis): when blood vessels are damaged the platelets form a primary plug, which stops or slows down bleeding, while the clotting cascade generates fibrin to seal off the damaged area. In healthy patients, platelets live for 10–12 days. Platelets contain two types of granule: dense bodies and alpha-granules
86
The production of red cells from stem cells is driven by transcription factors.
What is a feature of GATA-2?
A) Forms a complex with Tal-1/SCL; responsible for producing blood when in utero
B) Found in association with multipotent progenitors; its absence leads to failure of erythroid cell production with cells not developing beyond the primitive proerythroblast
C) Found in multipotent stem cells; increased impression leads to proliferation of these cells and reduction results in loss of haematopoiesis
D) Overexpression leads to cells developing down the myeloid lineage
E) Though to be very important at the very early stages of erythropoiesis, at the multipotent or myeloid-erythroid stem cell level
C) Found in multipotent stem cells; increased impression leads to proliferation of these cells and reduction results in loss of haematopoiesis
Laboratory animals, such as zebrafish, provide the opportunity for much molecular research. GATA-2 expression in this animal is associated with areas of haematopoiesis. It is also found on multipotent stem cells. Increased expression of GATA-2 leads to proliferation of these cells, and a reduction results in a loss of haematopoiesis.
87
Overexpression of which transcription factor leads to cells developing down the myeloid lineage?
PU.1
88
__?__ is found in association with multipotent progenitors; its absence leads to a failure of erythroid cell production with cells not developing beyond the primitive proerythroblast.
GATA-1
89
__?__ forms a complex with Tal-1/SCL; responsible for producing blood when in utero
Rbtn2/LMO2
90
The rate of production of red cells is governed by erythropoietin.
From which organ is erythropoietin secreted?
```
A) Kidney
B) Bone marrow
C) Spleen
D) Heart
E) Lungs
```
A) Kidney
Erythropoietin is a glycosylated protein of 165 amino acids produced by the kidney (90%), and to a lesser extent by the liver.
91
Normal red cells live for around 120 days, showing signs of age towards the end of this time.
What is the fate of an old red cell?
A) ATP levels decrease and glycolysis slows down
B) Become more flaccid
C) Engulfed by neutrophils
D) Make their way towards the liver for engulfment
E) Membrane lipid levels rise
A) ATP levels decrease and glycolysis slows down
The fate of red cells as they age is:
* they become more rigid
* glycolysis slows down
* ATP levels fall
* membrane lipid levels reduce
* they gradually desiccate
* haemoglobin cross-links to spectrin
* antibodies are produced against neoantigens (new antigens) that have been revealed by ageing.
Senescent red cells are phagocytized and digested by macrophages in the spleen.
92
Where is 'the graveyard of red cells'?
Spleen
93
Which leukocyte engulfs senescent red blood cells?
Macrophages
94
Anaemia is a reduction in red cell haemoglobin concentration relative to that found in a population of similar age and sex. Anaemias usually have an underlying cause.
What type of anaemia is associated with renal failure?
A) Haemolytic anaemia
B) Macrocytic anaemia with megaloblastic marrow
C) Macrocytic anaemia with normoblastic marrow
D) Microcytic anaemia
E) Normocytic anaemia
E) Normocytic anaemia
95
Iron is a key component of haemoglobin. Haemosiderin is an insoluble form of storage iron.
In which of the following cells is haemosiderin found?
```
A) Erythrocytes
B) Macrophages
C) Basophils
D) Eosinophils
E) Platelets
```
B) Macrophages
Once absorbed from the bowel, iron is transported across the mucosal cell to the blood, where it is carried by the protein transferrin to developing red cells in the bone marrow.
Our bodies have two main types of iron store:
(i) ferritin, a readily accessible source of iron, and
(ii) Haemosiderin, an insoluble form of storage iron found mainly in macrophages.
Unbound transferrin, measured as the total iron binding capacity (TIBC) in plasma will be increased when iron levels are low.
96
DNA synthesis is impaired in megaloblastic anaemias. The metabolic pathway for DNA replication involves both vitamins B12 (cobalamin, Cbl) and folate.
In which of the following organs is cobalamin released?
```
A) Stomach
B) Duodenum
C) Jejunum
D) Ileum
E) Liver
```
A) Stomach
Cobalamin is released from food in the stomach.
* In the stomach Cbl is released from non-specific binding proteins due to the acid environment.
* Cbl then binds to pepsin-resistant R protein.
* In the duodenum trypsin digests the R protein and vitamin B12 is then bound to intrinsic factor (IF), which is produced by gastric parietal cells.
* Once it reaches the terminal ileum, the cobalamin–IF complex binds to a receptor, named ‘cubulin’ after the CUB domains that make up most of the protein. A CUB domain is a highly conserved sequence consisting of 110 amino acid residues and found in many regulatory proteins, but in a particularly high concentration in this protein.
* Cbl dissociates from IF and the Cbl is transported by transcobalamin II (TC II), which carries the B12 into the portal circulation.
* Transcobalamin II binds to specific receptors on the cell surface and is internalized. Then Cbl is released and the transport protein is degraded by cellular enzymes. Within the liver cell, Cbl acts as a coenzyme in the complex pathway leading to DNA synthesis.
97
Vitamin B12 deficiency can lead to neuropathy.
What is a consequence of vitamin B12 deficiency?
```
A) Neural tube defects in a fetus
B) Optic neuritis
C) Subacute degeneration of the spinal cord
D) Subsclerosing panencephalitis
E) Wernicke’s encephalopathy
```
C) Subacute degeneration of the spinal cord
Vitamin B12 deficiency leads to subacute combined degeneration of the spinal cord, and folate deficiency leads to neural tube defects in a fetus.
98
Anaemias may be caused by failures in absorption of essential nutrients, abnormalities of the red cells or failure of red cell production.
What is Fanconi’s anaemia?
A) Autoimmune condition with atrophic gastritis leading to loss of intrinsic factor required for absorption of vitamin B12
B) Autosomal recessive disease that results in skeletal, skin and organ abnormalities, and aplastic anaemia
C) Caused by the failure of the pluripotent stem cells
D) Impairment of DNA synthesis but not RNA synthesis
E) Rare defect of red cells that makes cells vulnerable to destruction by activated complement
B) Autosomal recessive disease that results in skeletal, skin and organ abnormalities, and aplastic anaemia
Fanconi’s anaemia is an autosomal recessive disease that results in skeletal, skin and organ abnormalities, as well as an aplastic anaemia. Several genes on different chromosomes are involved in making a complex essential for DNA repair. Individuals with this condition have cells that are hypersensitive to genotoxic agents, such as mitomycin. Cells are seen to have increased chromosome breaks.
99
What is paroxysmal nocturnal haematuria?
A rare defect of red blood cells that makes them vulnerable to destruction by activated complement
100
Deficiency in which vitamin impairs DNA synthesis but not RNA synthesis?
Vitamin B12
101
Like most cell membranes, the red cell membrane is a lipid bilayer made up of phospholipids, cholesterol and glycolipids.
What is not a principal cytoskeletal protein of a red cell membrane?
```
A) Actin
B) Ankyrin
C) Protein 4.1
D) Spectrin
E) Valine
```
E) Valine
Spectrin is the major structural protein in the red cell membrane. It is 100 nm long, is highly pliable, and comprises two subunits: alpha and beta. Each subunit is made up of tandem repeats (106 amino acid repeats). The subunits are aligned side by side and form heterodimers, cross-linked at their tail ends by actin filaments. The membrane cytoskeleton is linked to integral proteins in the lipid bilayer by ankyrin and protein 4.1. Ankyrin binds to beta-spectrin near a self-association site and links it to the cytoplasmic portion of band 3. This meshwork of proteins that underlies the plasma membrane restricts the lateral mobility of the integral proteins.
102
Red cell enzymes maintain the integrity of red cells. Defects can lead to haemolysis.
What is the most common red cell enzyme defect?
```
A) 5’ nucleotidase
B) Cytochrome b5 reductase
C) Glucose-6-phosphate dehydrogenase
D) Lactic dehydrogenase
E) Pyruvate kinase
```
C) Glucose-6-phosphate dehydrogenase
G6PD deficiency is the commonest red cell enzyme defect leading to haemolytic anaemia. The enzyme plays an important role as part of the pentose phosphate pathway (hexose monophosphate shunt), reducing NADP to NADPH.
103
Adult haemoglobin (HbA) is a tetramer (2 alpha-like + 2 beta-like globins) associated with a haem group. Fetal haemoglobin (HbF) is different.
What is the haemoglobin structure of fetal haemoglobin (HbF)?
```
A) alpha-2-beta-2
B) alpha-2-beta-S2
C) alpha-2-beta-S-beta-C
D) alpha-2-delta-2
E) alpha-2-gamma-2
```
E) alpha-2-gamma-2
104
In health, the bone marrow regulates the number of cells in the peripheral blood to match requirements. Marrow malfunction may lead to production of excess numbers of cells (myeloproliferative disease), or functionally defective cells (myelodysplastic syndromes). Leukaemia is a myeloproliferative disease in which there are enormous numbers of white cells in the peripheral blood.
What is a feature of chronic myeloid leukaemia?
A) Clonal expansion of lymphoid cells, mainly B cells
B) Commonest adult leukaemia
C) Mainly affects children
D) Malignant plasma cells accumulate in the bone marrow and suppress cell production
E) Uncommon clonal stem cell disorder making up 15% of all leukaemias
E) Uncommon clonal stem cell disorder making up 15% of all leukaemias
* Acute myeloid leukaemia (AML) occurs mainly in adults and acute lymphoblastic leukaemia (ALL) affects mainly children.
* Chronic myeloid leukaemia (CML) is an uncommon clonal stem cell disorder making up 15% of all leukaemias. Presentation is more common in adults between the ages of 40 and 60 years.
* Chronic lymphocytic leukaemia (CLL) is the commonest adult leukaemia in Western societies with a peak incidence in patients aged between 60 and 80 years of age, and a male to female ratio of 2:1. CLL is a slow-growing disorder characterized by progressive accumulation of neoplastic cells in the bone marrow, spleen, liver and lymph nodes.
105
Viral infection can lead to a chronic antigenic stimulation and dysregulation of cytokines, resulting in B or T cell proliferation. Several viruses are implicated and their geographical locations may influence the development of lymphomas.
What virus is not implicated in lymphomas?
```
A) Epstein–Barr virus
B) Hepatitis C virus
C) Herpes simplex
D) Human T-cell leukaemia virus type 1
E) Kaposi’s sarcoma-associated herpes virus
```
C) Herpes simplex
106
Endothelial cells line all blood vessels and these play a central role in preventing unwanted thrombosis. The endothelium provides an effective barrier between the thrombogenic subendothelial cells and the blood coagulation factors
What is the function of thrombomodulin?
A) Encourages platelet aggregation
B) Inhibits thrombin
C) Involved in the control of thrombin
D) Potent inhibitor of platelet aggregation
E) Released from the activated platelet and causes vasoconstriction
C) Involved in the control of thrombin
Other endothelial agents include:
* Heparin sulphate: this is a naturally occurring heparin that leads to inhibition of thrombin.
* Enzymes: these degrade platelet-derived molecules, such as adenosine triphosphate (ADP), the latter encouraging platelets to aggregate.
* Prostacyclin and nitric oxide (NO), which are potent inhibitors of platelet aggregation, discouraging platelets from sticking to the vessel wall.
107
Blood group antigens are usually found on red cells. There are 26 blood group systems, of which the most important in transfusion medicine are ABO and Rhesus.
What antibodies are found in people with blood group O?
```
A) Anti-A
B) Anti-B
C) Anti-O
D) Anti-A and anti-B
E) None
```
D) Anti-A and anti-B
No such thing as anti-O
Group A have anti-B antibodies
Group B have anti-A antibodies
Group AB have no antibodies
108
Coordination of growth factors for haemopoiesis is controlled by hormones and their interaction with specific receptors.
What is a function of interleukin 3 (IL3)?
A) Acts with other growth factors on early progenitors to produce mature red cells, granulocytes, monocytes and platelets
B) Directed at producing neutrophils
C) Responsible for erythroid development
D) Responsible for megakaryocytic development
E) Targeted at monocyte growth and development
A) Acts with other growth factors on early progenitors to produce mature red cells, granulocytes, monocytes and platelets
109
Dietary deficiency is seldom the cause of iron deficiency anaemia.
Which of the following infections can lead to iron deficiency?
```
A) pneumonia
B) meningitis
C) hookworm infestation
D) hepatitis
E) Japanese encephalitis.
```
C) hookworm infestation
Hookworm infestation is the most common infestation to cause iron deficiency anaemia.
110
Lymphoid tissue is found throughout the body, and acts to protect the body against foreign antigens.
What is not lymphoid tissue?
```
A) Lymph nodes
B) Mediastinum
C) Spleen
D) Thymus
E) Tonsils
```
C) Spleen
Spleen is not lymphoid tissue. Lymphoid tissues in the body include the tonsils, the thymus gland, the mediastinum and the lymph nodes.
111
Coagulation disorders may be inherited or acquired, and are the result of deficient or defective functioning of coagulation factors.
What coagulation factor is deficient in haemophilia A?
```
A) von Willebrand factor
B) Factor V
C) Factor VII
D) Factor VIII
E) Factor IX
```
D) Factor VIII
Haemophilia A is an inherited X-linked disorder where mutations within the factor VIII gene lead to defective function of the factor VIII-C molecule in the coagulation cascade.
112
Coagulation disorders may be inherited or acquired, and are the result of deficient or defective functioning of coagulation factors.
What is Bernard–Soulier syndrome?
A) Abnormality in platelet Gp IIb-IIIa interaction preventing platelet aggregation
B) Autosomal dominant inherited disorder (although some forms are recessive) associated with a deficiency in circulating von Willebrand factor (vWF)
C) Autosomal recessive inherited disorder where there is reduced complex of Gp1b, factor IX, and factor V which serves as a receptor for vWF leading to lack of platelet plug formation
D) Inherited X-linked disorder where mutations within the factor VIII gene lead to defective function of the factor VIII-C molecule in the coagulation cascade
E) Inherited X-linked disorder where mutations within the factor IX gene lead to defective function of the factor IX molecule in the coagulation cascade
C) Autosomal recessive inherited disorder where there is reduced complex of Gp1b, factor IX, and factor V which serves as a receptor for vWF leading to lack of platelet plug formation
113
Two major genes have been implicated in neoplasia: oncogenes and tumour suppressor genes. These occur through mutations, chromosome translocation or viral activation.
What disease is associated with the Philadelphia chromosome?
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A) Chronic myeloid leukaemia
B) Haemophilia B
C) Hodgkin’s lymphoma
D) Myelofibrosis
E) Polycythaemia
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A) Chronic myeloid leukaemia
Chronic myeloid leukaemia (CML) is an uncommon clonal stem cell disorder making up 15% of all leukaemias. Presentation is more common in adults between the ages of 40 and 60 years. CML is characterized by a high white cell count, of granulocytic lineage, and the presence of the Philadelphia chromosome (Ph).
114
Sickle cell disease is highly variable. Many patients have few symptoms, since Hb S has reduced O2 affinity and oxygen is given up more easily, although they are often severely anaemic. The anaemia is chronic, however, and patients are generally well adapted until an episode of decompensation occurs, resulting in a sickle cell crisis and an accompanying severe haemolytic anaemia.
Which of the following can precipitate sickle cell crisis?
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A) Weight gain
B) Ingestion of fava beans
C) Severely anaemic infant failing to thrive
D) Inhalation of 100% oxygen
E) Hypoxia
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E) Hypoxia
Precipitants of sickle cell crisis include:
* Infection
* Dehydration
* Cold
* Hypoxia
* Acidosis
115
What is the role of fibrinogen in platelet plug formation?
A) Tethering
B) Adhesion
C) Aggregation
D) All of the above
C) Aggregation
