Biosci 107 - blood and immune

What is the average human blood volume?

5 litres

What does blood pressure ensure?

- Even and efficient flow through capillaries
- Low enough pressure to prevent capillary leakage but high enough pressure to avoid coagulation (clotting)

What does blood provide?

A one way pressurised system for transport

What does blood transport?

Oxygen, proteins, glucose, lipids and essential oils which are required for normal cell function

How is arterial pressure maintained?

Maintained by elastic vessel walls containing abundance of smooth muscle

Why is venous pressure lower than arterial pressure?

As the veins contain less smooth muscle where one way valves are required to prevent back flow

Why does blood volume need to be maintained?

So that pressure can be retained

How much blood loss is fatal and why?

When over 20% of blood is lost it can be fatal as pressure and flow is impaired and so tissue is starved of oxygen and other nutrients

How is high pressure caused?

Hypertension also known as high pressure is caused by the narrowing or hardening of arteries.

What does high pressure result in?

Reduced blood flow and occult coagulation (clotting) that can lead to blood clots in the brain and stroke

How is oxygen carried between the lungs and tissues?

Carried by haemoglobin (oxyhaemaglobin) which is the major protein in red blood cells

How much of the total blood volume do red blood cells make up?

About 45%

What is systolic pressure?

When the blood is fully compressed. So the left ventricle is squeezed at its tightest and the artery is expanded to its greatest.

How much of the red blood cells dry weight does haemoglobin constitute?

About 96%

What does each haemoglobin molecule contain?

Contains 4 haem molecules each containing 1 iron atom in the ferrous form (Fe2+)

Why does oxygen bind to haemoglobin rather than simply dissolving in blood?

Red blood cells bind oxygen with 70X greater capacity than if O2 was simply dissolved in blood

What is the partial pressure (pO2) of the lungs? And what does diatomic oxygen do under this pressure?

~100 mm Hg and under this pressure diatomic oxygen freely associated with Fe2+

What happens when the partial pressure of the lungs drops in the tissue?

O2 dissociates and is replaced by increased concentration of CO2 which is a by product of respiration

What compounds bind Fe2+ better than oxygen?

Carbon monoxide (CO) and cyanide (CN)

How does cyanide stop heart muscle activity?

Cyanide targets the Fe2+ containing mitochondrial cytochrome C oxidase which is essential for respiration

What is the colour of normal oxygenated blood containing oxyhaemaglobin?

Bright red (contains O2)

What is the colour of venous blood containing carbamihaemaglobin?

Dark red (contains CO2)

What is the colour of carbon monoxide poisoned blood containing carboxyhaemaglobin?

Cherry red (contains CO)

What colour is cyanide poisoned blood containing cyanohaemaglobin?

Pink (containing CN)

Why is blood homeostasis important?

Maintaining a stable blood acid/base balance is very important. Normally the pH is 7.4 and if there is a pH variance of 0.2 either way or more results in stress. Also known as acidosis and alkalosis

What is acidosis?

Increased acidity in the blood and other tissues

What is alkalosis?

Excessive blood alkalinity

What effectively buffers blood?

Buffered by albumin, phosphate, bicarbonate, creatinine and other compounds

What 3 compounds does blood separate into upon low speed centrifugation?

1. Packed red cells (40%)
2. Buffy coat (10%) containing white cells
3. Plasma (50%) contains soluble proteins, lipids and platelets

What is plasma?

It is the liquid fraction of uncoagulated blood and it is very viscous

What remains after blood has been coagulated?

Serum remains and it is normally a straw yellow colour but can be cream colour if you've had a fatty meal.

What is fibrinogen?

Fibrinogen is a glycoprotein that helps in the formation of blood clots. Fibrinogen is absent from serum as it had formed the insoluble fibrin clot.

How is blood separated (other than centrifugation)?

Blood can be separated by electrophoresis where serum is separated in an electric field into 5 protein fractions - albumin, a 1, a 1, B and y

What are the major proteins of blood?

Albumin, fibrinogen, immunoglobulins, complement (C') proteins and coagulation proteins

What is albumin?

A protein that makes up 50% of total blood protein.

What is the primary function of albumin?

maintaining colloidal osmotic pressure but also binding and transporting many small molecules and proteins. Also a major binder of pharmaceutical drugs

What is fibrinogen protein?

The second most abundant protein of blood. It is cleaved by the protease thrombin to form small cross linked fibrin that forms blood clots

What are immunoglobulins?

Proteins found in the y fraction and are responsible for humoral immunity (portion of immunity mediated by macromolecules). They constitute ~10% of total blood protein.

How are immunoglobulins produced?

By plasma cells which are a form of end-stage B lymphocytes

In what kind of disease are immunoglobulins elevated?

multiple myeloma which is a cancer in plasma cells

What are complement (C') proteins?

A group of zymogens essential for phagocytosis. The most abundant is C3 but there are C1-C9 components. Complement proteins are stable as zymogens but are unstable when cleaved and break down rapidly

What are coagulation proteins?

A set of 13 proteins that initiate the cleavage of fibrinogen to fibrin and cross linking to form the clot. Thrombin is the central enzyme that cleaved fibrinogen

What are the types of blood cells and what are their functions?

1. Erythrocytes (most abundant) -carry oxygen
2. Leukocytes (least abundant) -essential for immunity
3. Platelets (second most abundant) -coagulation and tissue repair

What are erythrocytes?

Red blood cells that are solely for oxygen transport. They don't have a nucleus so survive radiotherapy much better because there is no DNA

What are myeloid cells?

Myeloid cells include monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, dendritic cells, and megakaryocytes or platelets. .

What do myeloid cells provide?

innate immunity and phagocytosis is a key mechanism

What do myeloid cells have?

complement receptors and Fc receptors that bind immune complexes.

Microbes cannot be phagocytised until....?

they have been opsonised ("buttered") with complement proteins

What are all the types of myeloid cells?

1. Neutrophils
2. Monocytes (macrophage)
3. Basophils
4. Eosinophils

What are the types of lymphoid cells?

1. B lymphocytes (antibodies -adaptive immunity)
2. T lymphocytes (cellular - adaptive immunity)

What is haematopoiesis?

Also known as haemopoiesis which is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells/pluripotent (capable of giving rise to several different cell types) human stem cell (HSC) found mainly in the bone marrow.

What is haematopoiesis characterized by?

by the CD34 marker antigen. About 1 in 10,000 white cells are CD34+. They are more abundant in placental cord blood.

In medicine what are human stem cells used for?

They are used to re-populate leukaemia patients after autologous bone marrow transplant. They are selectively removed with an anti-CD33 antibody from the patient prior to radio-ablation, then given back along with stimulating factors like GM-CSF, G-CSF to speed up re-population of white blood cells which are critical to prevent infection

What two multi potent stem cells do CD34+ HSC give rise to?

Myeloid and lymphoid progenitors

What cells do myeloid progenitors give rise to?

Mast cells, megakaryocytes, myeloblasts and erythrocytes

What cells do lymphoid progenitors give rise to?

B lymphocytes and T lymphocytes

What do T lymphocytes give rise to?

CD4 and CD8

What do myeloblasts differentiate into?

Monocytes, eosinophils, neutrophils and basophils

What is complement?

A set of 9 major plasma proteins that leads to opsonisation and phagocytosis of foreign organisms. There are 3 pathways to activate complement.

What is the third pathway to activate complement?

3) lectins - lectins are carbohydrates binding proteins that bind to unusual carbohydrates unique to the microbe. This activates a similar convertase to the classical pathway

What is the first pathway to activate complement?

1) classical pathway - antibody (IgM or IgG) binds to the surface of microbe. C1q binds to Fc region of the bound antibodies activating C2, C4 and C3 to form a covalently bound C3 concertise on the microbe surface.

What is the second pathway to activate complement?

2) alternative pathway - complement C3 is activated just by being close to the surface. This activates another type of C3 convertase

What is the end stage complement?

When the surface bound convertases activate complement C5 that forms a pore with C6, 7, 8 and 9. This pore inserts into some bacterial membranes to cause lysis. This is called MAC or membrane attack complex

What is the membrane attack complex (MAC) also known as terminal complement complex (TCC)?

It is a structure typically formed on the surface of pathogenic bacterial cells as a result of the activation of the host's alternative pathway, classical pathway, or lectin pathway of the complement system, and it is one of the effector proteins of the immune system.

What does MAC form?

transmembrane channels. These channels/pores insert into some bacterial membranes/disrupt the cell membrane of target cells, leading to cell lysis and death.

What is opsonisation?

an immune process where particles such as bacteria are targeted for destruction by an immune cell known as a phagocyte . The process of opsonization is a means of identifying the invading particle to the phagocyte.

Large vessles....

high volume/low flow

Small vessels....

low volume/high flow

Blood pressure ensures....

1. Even and efficient flow through the small capillaries.
2. Low enough to prevent capillary leakage but high enough
to avoid coagulation.

What are the major components of blood?

1. Cells -erythroid, myeloid and lymphoid.
2. Proteins - albumin, haemoglobin, fibrinogen,
immunoglobulins are the major plus many others.
3. Lipids bound in lipoproteins HDL, LDL, VLDL
4. Electrolytes, salts and minerals (HCO3
-, Na+, Cl-,
Ca++, Mg++, K+
, creatine, creatinine).
5. Vitamins, hormones.
6. Glucose.

What is CD34?

CD34 is a surface antigen marker on HSCs. An
anti-CD34 antibody can select and concentrate
HSCs from blood prior to a bone marrow
transplant.

Adaptive immunity is given by?

-B lymphocytes
-T lymphocytes

What is innate immunity?

Neutrophils, monocytes (macrophages), basohpils and eosionophils

GM-CSF (Granulocyte macrophage
colony-stimulating factor) is one of the important drivers for haematopoiesis. What is it?

-Produced by macrophages, T
cells, endothelial cells and
fibroblasts.
-Stimulates production of
neutrophils, eosinophils,
basophils and monocytes.

EPO (erythroprotein) is one of the major drivers of haematopoiesis. What does it do?

-Drives production of
erythrocytes
-Produced mainly by the
kidney during adulthood and
liver in perinatal.

G-CSF
Granulocyte colony-stimulating
factor is one of the major drivers of haematopoiesis. What does it do?

-Produced by many different cells.
-Stimulates production of
granulocytes but also acts to
mature neutrophils

Complement is......

a proteolytic activation cascade and is essential for innate immunity. It tags invading organisms so that they can be phagocytosed.

What is the most abundant complement component in serum.

C3

How can complement be activated?

By 3 diff pathways. The classical pathway is mediated by antibodies IgM or IgG binding to a microbe surface which is then bound by complement C1.

What is the deposition of the complement on microbes essential for?

Phagocytosis - called opsonisation

What are deposited complexes called?

Convertases. These activate more complement that then
deposits to coat the surface.

How are convertases irreversibly bound?

Via a covalent bound

What does cleavage of C3, C4 AND C5 produce?

small fragments (C3a, C4a and C5a) that are
powerful chemoattractants called anaphylotoxins that attract and activate neutrophils.

What are people with deficiencies in a complement component susceptible to?

Chronic infections

What kind of proteins do microbes produce?

virulence factors that inhibit the complement cascade.

What are two pathways for activation in coagulation?

• Intrinsic caused by contact with surfaces
• Extrinsic caused by tissue damage.

What is factor X?

the key enzyme common to both these pathways

Why calcium essential?

Remove calcium and blood does not clot.

What do many parasites and other microbes that rely on blood flow produce?

powerful anticoagulants
that typically target the thrombin step.

What is plasminogen?

It is converted to active plasmin and dissolves the clot (thrombolysis).

What is thrombin?

an enzyme that cleaves fibrinogen to fibrin which cross links to form a blood clot

What does plasmin do?

Cleave the fibrin clot, resulting in thrombolysis

What are the anti-coagulants that block thrombin?

Heparin and warfarin are anti-coagulants that are used in med and many insects and parasites that rely on blood for food

What do all living things have the ability to do?

Discriminate between self and non-self

What kind of response does our innate immunity provide?

First-line or immediate response to pathogen invasion

Innate immunity is what compared to adaptive immunity?

More primordial (occurred 500 million years ago)

In mammals, innate immunity is highly developed with 3 interlinked processes, what are they?

-Complement
-Myeloid cells and phagocytosis (neutrophils)
-Pattern recognition receptors (PRR)

Describe the memory of the innate response

Innate response has no memory

What is in the cellular innate system?

Cells - eosinophils, neutrophils, macrophages, mast cells, natural killer cells, dendritic cells

What is the humoral innate system made of?

Soluble factors - antimicrobial peptides and anitbodies