Haematology Flashcards
What is haptoglobulin and what do high levels of it suggest?
It is an alpha 2 globulin in the plasma and binds to haemoglobin release from dead erythrocytes to from haptoglobulin-haemoglobin complexes which are removed by the spleen
High levels of haptoglobulin suggest haemolytic anaemia - where RBCs are destroyed faster than they are made
What are the gamma globulins of the plasma and what do high levels of them suggest
C reactive protein and immunoglobulins
High levels suggest infection or myeloma (a blood cancer which develops from cells in bone marrow)
What is the main difference between plasma and interstitial fluid?
Plasma contains more protein than interstitial fluid
What is haemopoiesis
The formation and development of blood cells
What is haemopoiesis regulated by
Genes
Micro environment
Transcription factors
Growth factors (glycoprotein hormones which bind to cell surface receptors that regulate proliferation and differentiation of HSCs and regulated function of mature blood cells)
What is the erythropoiesis growth factor
Erythropoietin
What are the granulocyte and monocyte production growth factors
G-CSF
G-M CSF
cytokines eg interleukins
Megakaryocytopoiesis and platelet production growth factor
Thrombopoietin
What other cells/structures are distributed with HSCs in the bone marrow?
In the bone marrow HSCs interact with
- HSC progenitor cells
- mesenchymal stem cells
- endothelial cells
- vasculature
What can happen if the regulation of haemopoiesis is disrupted
The balance between proliferation and differentiation is disrupted and can get leukemia (due to too many cells) or bone marrow failure (due to not enough cells)
Life span of different blood cells
Erythrocytes - 120 days Platelets - 10 days Monocytes - several days Neutrophils - 7-10 hours Eosinophils- little less than neutrophils Lymphocytes - v variable
2 essential characteristics if HSCs
Can self renew - some daughter cells stay as HSCs to prevent HSC pool depletion
Can differentiate into mature progeny - other daughter cells can differentiate into other types of cells through myeloid or lymphoid progenitors
Changes in site of haemopoiesis between adult and foetus
1) in mesoderm of yolk sac
2) at 6-8 weeks of gestation, liver takes over
3) 10 weeks into gestation, bone marrow takes over. Adult haemopoiesis happens mainly in bone marrow esp in pelvis, femur, and sternum
What are polychromatic erythrocytes
Have a blue tinge due to high RNA content - lose ribosomes after a few days and become mature erythrocytes
What does it mean if we see nucleated RBCs in blood
There’s a high demand for bone marrow to produce RBCs so immature RBCs are being prematurely released into circulation
Overall progression of RBC development
In bone marrow: Common myeloid progenitor gives rise to proerythroblasts —> erythroblasts (have nucleus still)
In peripheral blood: erythroblasts —> reticulocytes (lost nucleus) —> erythrocytes
Where and how is erythropoietin (EPO) made and how does it work
Made in the kidneys in response to hypoxia and anaemia. Works by supply and demand feedback
Hypoxia or anaemia in kidneys makes kidneys produce EPO
EPO interacts with erythropoietin receptors on red cell progenitor membranes which increases bone marrow activity, causing bone marrow to produce more red cells
What is iron needed for in the body
1) Oxygen transport
2) mitochondrial proteins
- cytochrome a,b,c (for ATP synthesis)
- cytochrome P450 (for hydroxylation reactions)
Iron is important for healthy hair skin nails and mucous membranes
Where is iron absorbed
Duodenum
What is the best absorbed form of iron, and what does the other form of iron need for absorption
Haem (ferrous / Fe2+ ) is best absorbed
Non haem (ferric / Fe3+) needs reducing substances like vitamin C
(sources of non haem iron such as soya beans contain phytates which reduce absorption)
Why is iron haemostasis needed
Excess iron can be toxic to organs like liver and heart
There is no physiological mechanism that excretes iron so it’s absorption must be controlled to 1-2 mg absorbed per day from diet
What is transferrin
The transport protein in plasma that delivers iron to bone marrow fro erythropoiesis and for its use in enzymes and muscles
How does erythropoietic activity affect hepcidin synthesis and what does this do
It suppresses hepcidin synthesis which ensures iron supply by increasing ferroportin in the duodenum enterocyte - this increases iron absorption
What does ferroportin do
It’s a transmembrane protein that transports iron from inside to outside of cell
What is an enterocyte
Cell of intestinal lining
What happens when iron storage is high
When ferritin stores are full, hepcidin production increases
The hepcidin binds to and degrades ferroportin
This stops ferroportin transporting iron out of the enterocytes
So iron stays in enterocyte - this allows iron to be disposed of as soon as enterocyte dies and is shed into the gut lumen
How can chemicals released during inflammation or chronic disease cause anaemia
Pro inflammatory cytokines ( IL-6, IL-1 TNf alpha, IFN gamma)
- decrease EPO production
- increase hepcidin production
This causes reduced Fe transport availability and absorption, resulting in anaemia of inflammation/chronic disease
What is hepcidin
A hormone that regulates iron ABSORPTION in the GUT
What is another name for vit B12
Cobalamin
How can vit B12 or floats deficiency affect rapidly dividing cells
Vit B12 and folate are needed for dttp synthesis (an important precursor for making thymidine DNA synthesis)
So deficiency in them means DNA synthesis is inhibited
This can cause megaloblastic anaemia (production of megaloblasts - abnormally shaped large RBCs)
This affects rapidly dividing cells such as
- cells in bone marrow - can grow but not divide
- epithelial surfaces of mouth and gut
- gonads - nerves
How is vitamin B12 absorbed
B12 binds to intrinsic factors (IF) in gastric parietal cells
B12-IF binds to receptors in ileum
Causes of B12 deficiency
Malabsorption - coeliac disease
Low B12 intake - veganism
Low IF secretion - pernicious anaemia
Lack of stomach acid - achlorhydria
How do erythrocytes die
Get destroyed by macrophages of spleen after 120 days
The iron is returned to bone marrow by transferrin and recycled there
Death releases bilirubin - excreted in bile
Where is folic acid absorbed
Small intestine (duodenum and jejunum )
When do folic acid requirements increase
Pregnancy
Increased RBC production eg sickle cell anaemia
A patients results show she has folate deficiency. What changes in the RBCs would you expect to see and why
Presence of macrocytes
As a result of impaired DNA synthesis which causes the cells to lack the DNA to divide but to continue to grow - causes megaloblastic erythropoiesis
What is the most abundant cytoskeleton protein if erythrocytes
Spectrin
What is the advantage if the biconcave shape of RBCS
Increases manoeuvrability through small blood vessels
Incraeses ability to RELEASE O2
Where does haemoglobin originate
The haem component is synthesised in mitochondria
The glob in component is synthesised in RER
Found exclusively in RBCs
What is the structure of the haem group
Ferrous iron (Fe2+) bound by a porphyrin ring - each Fe2+ can bind to one O2 molecule
Where does the globin component of haemoglobin come from in haemoglobin
There are 8 functional globin chains which are encoded by several genes separated into 2 gene clusters - the alpha globin cluster and the beta globin cluster
Alpha cluster - zeta and alpha genes
Beta cluster - delta, epsilon, beta and gamma genes
What is the secondary and quaternary structure of Hb
Secondary: 75 percent of the alpha and beta chains are in alpha helix form
Quaternary: 4 globin chains and 4 haem groups
Forms a tetramer (4 subunit protein)
Hydrophobic core and hydrophilic outside
Forms an approximate sphere
What is the majority of Hb in healthy adults
HbA - 2 Alpha and 2 beta
What is HbA2 and HbF made of
HbA2 = 2 alpha 2 delta HbF = 2 alpha 2 gamma
What is the p50 value and how does it differ between myoglobin and haemoglobin
P50 = the partial pressure of oxygen at which 50 percent of the haem groups are saturated with oxygen
P50 values:
Myoglobin = 2 torr
- has greater affinity for o2
- saturated at lower pp of o2
- produces a hyperbolic curve
- reacted to its function as its found in muscle
Haemoglobin = 26 torr
- lower affinity for o2
- produces a sigmoidal curve
- Positive cooperativity
- saturated at higher pp of o2
What allosteric effectors affect haemoglobins affinity for o2 and how
2,3-BPG (aka 2,3-DPG)
- formed by phosphorylation of 1,3-BPG by diphosphoglycerate mutate (DPGM) via Rapoport Luebering shuttle
- binds to site on haemogloblin distant from haem groups and stabilises the structure, lowering the haemoglobins affinity for oxygen - thus causes it to have sigmoidal dissociation curve
H+ (released from formation of lactate which replenishes NAD+ stores) and CO2 (formed from decarboxylation of pyruvate)
- bind to sites away from haem groups and lower affinity for oxygen
- BOHR effect
- so a decrease in pH of blood will mean more O2 is released into tissues
What is Absorbance
A = log 10
= the fraction of light transmitted through a blank solution/test solution
(So If solution has absorbance of 1.0, 10 percent of light is transited and 90 percent is absorbed)
What is the beer lambert law
Absorbance = the extinction coefficient x the concentration of the absorbing substance x the path length
describe the role of myoglobin and how it’s properties allow it to carry out this role
It is an oxygen binding molecule found in muscle, with one name group
It’s high affinity for o2 (higher than haemoglobin) allows it to carry out this role
But it’s lack of cooperativity means that it is poor at releasing o2