ICS Flashcards
Define inflammation.
A local physiological response to tissue injury.
Give a benefit of inflammation.
Inflammation can destroy invading micro-organisms and can prevent the spread of infection.
Give a disadvantage of inflammation.
Inflammation can produce disease and can lead to distorted tissues with permanently altered function.
Define exudate.
A protein rich fluid that leaks out of vessel walls due to increased vascular permeability.
What are the 5 cardinal signs of inflammation?
Rubor - redness - due to dilation of small BV
Dolor - pain - from stretching and distortion of tissues due to inflammatory oedema and pus putting pressure in an abscess cavity
Calor - heat - due to increased blood flow (hyperaemia) and systemic fever
Tumor - swelling - resulting from oedema and to a lesser extent the inflammatory cells migrating into the area
Loss of function
What are the stages of acute inflammation?
Increase vessel calibre - inflammatory cytokines and endogenous chemical mediators (bradykinin, prostcyclin and NO) mediate vasodilation.
Fluid exudate - Vessels become leaky and protein rich fluid is forced out of the vessel leading to swelling
Cellular exudate - neutrophils become abundant in this exudate
What is neutrophil action in acute inflammation?
- Margination - Due to increase in plasma viscosity and slowing of flow due to injury, neutrophils migrate to plasmatic zone
- Adhesion - selectins bind to neutrophil and cause rolling along the blood vessel margin
- Emigration and diapedesis - Movement of neutrophils out of the blood vessel through or in between the endothelium and basal lamina (other inflammatory cells follow)
- Chemotaxis - movement towards site of inflammation along chemical gradients
What is the action of neutrophils at the site of inflammation?
Bind to the pathogen and start phagocytosis
Lysosomes move to fuse with the neutrophil to form the phagolysosome
This releases lytic enzymes to kill the pathogen.
Macrophages then clear the debris
What are the outcomes of acute inflammation?
Resolution - initiating factor is removed and the tissue can return to normal structure and function
Suppuration - formation of pus (collection of leukocytes) surrounded by a pyogenic membrane to start the healing process (leads to scarring)
Organisation - Granulation tissue forms and you get the development of fibrosis
Progression - Excessive recurrent inflammation can become chronic and you get fibrotic tissue forming.
What are granulomas?
Aggregates of epitheliod histocytes (mainly macrophages) at the site of inflammation to contain the pathogen
How can acute inflammation be diagnosed histologically?
By looking for the presence of neutrophil polymorphs.
Give 3 endogenous chemical mediators of acute inflammation.
- Bradykinin.
- Histamine.
- Nitric Oxide.
What are 4 systemic effects of acute inflammation?
- Fever.
- Feeling unwell.
- Weight loss.
- Reactive hyperplasia of the reticuloendothelial system.
Give 6 causes of acute inflammation.
- Microbial infections (bacteria and viruses).
- Chemicals (corrosives, acids/alkalis).
- Physical agents (trauma, burns, frost bite).
- Hypersensitivity reactions (TB).
- Bacterial toxins.
- Tissue necrosis.
What cells are involved in chronic inflammation?
Macrophages and plasma cells (B and T lymphocytes).
What cell can form when several macrophages try to ingest the same particle?
Multinucleate giant cell.
Give 4 causes of chronic inflammation.
- Primary chronic inflammation.
- Transplant rejection.
- Recurrent acute inflammation.
- Progression from acute inflammation.
What can cause primary chronic inflammation?
- Infective substances having resistance to phagocytosis e.g. TB, leprosy.
- Endogenous materials e.g. uric acid crystals. necrotic tissue
- Exogenous materials e.g. asbestos.
- Autoimmune diseases e.g. chronic gastritis, rheumatoid arthritis etc.
- Other chronic inflammatory diseases e.g. chronic inflammatory bowel disease.
What are some macroscopic features of chronic inflammation?
- Chronic ulcer.
- Chronic abscess cavity.
- Granulomatous inflammation.
- Fibrosis.
What is granulation tissue?
Granulation tissue is composed of small blood vessels in a connective tissue matrix with myofibroblasts.
It is important in healing and repair of chronic inflammation
What condition causes granulomas with central necrosis?
Caseous granuloma (soft cheese like)
Caused by TB
What conditions cause granulomatous inflammation without central necrosis?
Sarcoidosis, leprosy, vasculitis, chrons disease
What blood marker is released from granulomas?
ACE
What is the difference between resolution and repair?
Resolution is when the initiating factor is removed and the tissue is able to regenerate. In repair, the initiating factor is still present and the tissue is unable to regenerate.
Name 5 types of cells capable of regeneration.
- Hepatocytes.
- Osteocytes.
- Pneumocytes.
- Blood cells.
- Gut and skin epithelial cells.
Name 2 types of cells that cannot regenerate.
Myocardial cells
Neurons
Define abscess.
Acute inflammation with a fibrotic wall.
Define thrombosis.
Formation of a solid mass from blood constituents in an intact vessel in the living.
Give 2 reasons why thrombosis formation is uncommon.
Laminar flow of blood
Endothelium is non-sticky
What are the 3 factors that can lead to thrombosis formation (virchow’s Triad)
- Change in vessel wall. (endothelial injury)
- Change in blood constituents. (platelet aggregation, thrombus formation or fibrin deposition)
- Change in blood flow. (stasis of blood flow)
Define embolus.
A mass of material (often a thrombus) that is carried in the vascular system that is able to become lodged in a vessel and block it.
Define ischaemia.
Decreased blood flow to tissues w/o other complications
Define infarction.
Decreased blood flow to a tissue that results in subsequent cell death.
Define Acute inflammation
Initial Response to tissue injury
Inflammation that is:
sudden onset,
lasts for a short duration and usually resolves
Involves Neutrophils and Monocytes
How do bacteria and viruses cause harm?
Bacteria - release exo/endotoxins that initiate the inflammatory pathways
Viruses - Intracellular replication causes cell death
What processes do the endogenous chemical mediators lead to?
Vasodilation
chemotaxis
increased vascular permeability
itching and pain
What are the main cell types in acute inflammation?
Neutrophil polymorphs
Macrophages
Fibroblasts
Endothelial cells
Lymphocytes
What are the main cell types in chronic inflammation?
Macrophages
Lymphocytes
Plasma cells
What is a multinucleated giant cell?
The cell that forms when several macrophages try to ingest the same pathogen and end up fusing together.
What are some differences between acute and chronic inflammation?
Chronic is persistent and the causative agent is often not removed
There tends to be less swelling
Inflammation and repair occurs at the same time
Fibrosis is a key feature
What is resolution?
Tissue restored to normal pre injury state tissue architecture is undamaged
tissue initiating factor is removed
What is lobar pneumonia
A bacterial infection caused by strep pneumonia one lobe of the lungs filled with pus and neutral polymorphs fill alveoli of the lungs this is resolved through antibiotics
What is healing by first intention?
- Edges of incision are brought together using stitches?
- The incision wound fills up with blood and a thrombus forms
- Exudation of fibrinogen causes the formation of weak fibrin.
- Epidermal growth, and collagen synthesis leads to a strong collagenous joint.
- Epidermis grows over the top.
What is healing by second intention?
When there is a gap or whole in the skin and there is tissue loss.
1. small blood vessels move in from the edges of the gap
2. fibroblasts enter the site of trauma and make collagen - granulation tissue
3. fibroblasts organise tissue to form organised collagen fibrils
4. early thrombus scar forms
5. Epidermis grows over the top and leaves a scar.
What are the constituents of a thrombus?
Platelets. Red blood cells, fibrin.
What are the stages of thrombosis?
Vasospasm
Platelet aggregation - VWF binds exposed collagen and platletes bind to this via GP1b. Then platelets aggregate by binding to each other through GP2a/3b
Clotting cascade.
What stimulates platelet aggregation?
Endothelial damage changes localised blood flow from laminar to turbulent.
Platelets come into contact with the endothelium and stick.
What are the different types of thrombosis and what causes them?
Arterial thrombosis - atherogenesis
Venous thrombosis - venous stasis
How would you treat an arterial and venous thrombosis?
Arterial thrombosis - Antiplatelets
Venous Thrombosis - Anticoagulants
What are the fates of a thrombosis?
Resolution - thrombus degrades and returns to normal
Organisation - Leaves scar tissue behind
Embolism - fragments of thrombi break off and get lodged in the circulation
Define embolism.
A solid mass in the blood vessel which causes a blockage to the vasculature.
What happens to an embolus if it enters the venous system?
- Filtered by the lungs
- Travels through the vena cava, though the right hand side of the heart and lodge somewhere in the lungs depending on size
- Blood vessels in the lung split down to capillary size so act as a sieve
What happens to an embolus if it enters the arterial system?
It will travel anywhere downstream of its entry point
Where may an infarct have a reduced impact?
on areas with a dual blood supply
Brain,
Liver
Lungs
what is an atheroma?
Focal thickening of the tunica intima arteries produced through the movement of ldls from the lumen.
How is an atheroma formed?
The ldls caused a cascade of events which, mediated through inflammatory response and smooth muscle cells proliferation leads to the development of obstructive fibrolipid plaque.
What is atherosclerosis?
Atheromas are plaque build-ups which obstruct that flow of blood. Atherosclerosis is the condition caused by atheromas, marked by arteries narrowed with and hardened by plaque causing CV complications, such as angina, myocardial/ cerebral infarction
What is an atherosclerotic plaque made up of?
Fibrous tissue
Lipid component - Cholesterol
Lymphocytes
FOAM cells
What are the stages of atherosclerotic plaque formation?
- Endothelial cell dysfunction
- Lots of cholesterol damages wall
- Endothelial cells directly injured
- High levels of LDL in the blood
- Can freely pass in + out of the wall
- At high concentration LDLs accumulate in the arterial wall and undergo oxidation
- Oxidised LDLs active the endothelial cells to:
- Release cytokines and growth factors
- Express adhesion molecule for leukocytes
- Attract macrophages + T helper cells
- Take up LDLs
- Macrophages
- Engluf oxidised LDLs to form foam cells (inflammatory response)
- Foam cells promote migration of smooth muscle cells from tunica media to tunica intima
- Increased population of smooth muscle cells leads to the increased sythesis of collagen (VIII) → hardened fibrous cap
- When foam cells die their lipid content is released, causing the formation of a collagenous lipid plaque
- Plaque occludes the lumen → leads to angina
- Eventually the plaque ruptures → leads to thrombosis and complete occusion of the vessel lumen
How does Atherosclerosis compare in a high and low-pressure vessel?
Atherosclerosis is never present in low pressure systems (pulmonary circulation) -but will form in high pressure vessels such as the systemic circulation
Name some system specific complications of atherosclerosis.
- Obstruction/ occlusion of arteries in the head and neck = cerebral infarction
- Obstruction/ occlusion of coronary artery = myocardial infarction
- Obstruction/ occlusion of artery in the limbs = peripheral vascular disease or gangrene
- Obstruction/ occlusion og renal arteries = increased renin release → increased blood pressure
- Atherosclerosis in the aorta can cause an aortic aneurysm, a result of excessive dilation of the aorta to the point that it rupture. Results in sudden death
why does aspirin help a patient if they have atherosclerosis?
Aspirin inhibits platelet aggregation, therefore reducing plaque formation.
What are the risk factors for atherosclerosis?
Age
gender
FHx
smoking
sedentary lifestyle
High cholesterol
Hyperlipidaemia
Hypertension
Diabetes
Define apoptosis
Non inflammatory programmed cell controlled death.
What are the steps of apoptosis?
Pyknosis - nucleus condenses
Blebs form - cell membrane becomes irregular
Apoptotic bodies form
cell membrane breaks off into fragments for easy phagocytosis
What are the mediators of apoptosis?
Caspases
What regulates the activity of caspases?
Intrinsic:
Bcl2 family of enzymes:
Bcl2 - inhibits apoptosis
Bax - promotes apoptosis
Extrinsic:
Fas
Binding of Fas ligand to the fas receptor induces apoptosis
What is necrosis?
Inflammatory unprogrammed traumatic cell death that induces inflammation and repair.
Define genetic disease.
A genetic disease is one that occurs primarily from a genetic abnormality.
Define congenital disease.
A disease which is present at birth.
Define inherited disease.
Caused by inherited genetic abnormality, it may not manifest itself until later life.
Define an acquired disease.
Caused by non genetic environmental factors that usually occurs after birth.
Define atrophy.
Decrease in tissue size caused by the decreased in number of constituent cells or a decrease in their size.
Define hypertrophy.
Increase in tissue size caused by an increase in the size of the constituent cells.
Define hyperplasia.
Increase in tissue size caused by an increase in the number of the constituent cells.
Define metaplasia.
Change in differentiation of a cell from one fully differentiated type to a different fully differentiated type.
Define dysplaysia.
Morphological changes seen in cells in the progression to becoming cancer.
Define carcinogenesis
The transformation of normal cells to neoplastic cells through permanent genetic alterations or mutations
This is a multistep process
What is a carcinogen?
A mutagenic agent known to cause cancer
Define carcinogenic?
Cancer causing
Define Oncogenic?
Tumour causing
Define oncogenesis?
The process by which normal cells transform into neoplastic cells
What is a neoplasm?
An autonomous abnormal persistent new growth that continues to grow after the initial growth stimulus has been removed.
What can neoplasms arise from?
They can only arise from nucleated cells
(eg. not RBCs but could arise from their precursors)
What is a tumour?
Any abnormal swelling
What percentage of cancer risk is environmental?
85%
What host risk factors will increase the risk of cancer?
Race
Diet
Sex
Age
Inherited predisposition
premalignant conditions
Transplacental exposure
Give examples of how race can affect cancer risk?
Oral cancer increase risk in SE asia releated to chewing betal nut and reverse smoking
Skin cancer risk is decreased in people with black skin as an increase in melanin is protective against UV.
Give some examples of inherited predispositions that will increase cancer risk?
Familial polyposis coli - increase risk of bowel cancer
Give some examples of premalignant conditions that will increase the risk of cancer?
Colonic polyps
Ulcerative colitis
Undescended Testis
Give an example of how transplacental exposure increased the risk of cancer
The daughters of mothers who took diethylstilboestrol for morning sickness had and increased risk of developing vaginal cancer
Name 5 different categories of carcinogens?
Viral
Chemical
Ionising and non-ionising radiation
Hormones, parasites and mycotoxins
Miscellaneous
Give some examples of viruses that cause cancer?
Hepatitis B anda C - HCC
HHV8 (human herpes virus 8) - kaposi sarcoma
HPV - Squamous cell carcinoma
EBV - Burkitts Lymphoma
HIV - cerebral lymphoma
How can hormones cause cancer?
increase in oestrogen can cause endometrial cancer
What parasite can cause cancer?
Shistosoma causes bladder cancer
What miscellaneous materials can cause cancer?
Asbestos
Metals - arsenic
What type of cancer do polyaromatic hydrocarbons cause and what exposes people to these?
Lung and skin cancer
Smoking and mineral oils
What cancer do aromatic amines cause?
bladder cancer
People who work with dye or rubber
What cancer do nitrosamine cause?
Gut cancer
What type of cancer do alkylating agents cause?
Leukaemias
Define Neoplasia?
A lesion resulting from new and abnormal tissue growth which persists independent of its initiating stimulus.
What are the two types of neoplasia?
Benign and malignant
How can neoplasias be classified?
By behaviour
By histogenesis
What are the features of a benign tumour?
Slow growing - low mitotic activity
Well circimuscribed - no invasion to surrounding tissue
Resemble cell origin - rarely necrose or ulcerate
Exophytic - grow outwards
what are some long-term effects of benign tumours?
Pressure on adjacent tissues
Obstruction of ducts/hollow organs
produce hormones
Can be pre-malignant
Anxiety
What are the features of a malignant tumour?
Fast growing - high mitotic activity and division rate
Poorly defined, irregular infiltrative borders - invasion of surrounding tissues (metastasis)
Variable resemblance to cell of origin - commonly necrosing or ulcerating
Endophytic growth - grow inwards.
What are some complications of malignant tumours?
Pressure on adjacent structures
form secondary tumours
Obstructory
very painful
blood loss
What is the structure of a neoplasm?
Neoplastic cell
Stroma
What are the features of neoplastic cells?
Always derived from nucleated cells
Usually monoclonal
Growth pattern related to parent cell
Synthetic activity related to parent cell - eg. hormone producing.
What is the stroma of a neoplasm?
Supported by connective tissue framework that provides mechanical and nutritional support. usually blood vessels.
What factors promote angiogenesis?
VEGF
Fibrobalst growth factor
What is the behavioural classification of neoplasms?
Benign
Borderline - defy precise classification
Malignant
What are the main histological classifications of tumours?
epithelial
Connective tissue
Lymphoid
Haematopoietic
What cancer does not have a stroma?
Leukaemia
What is a benign non-glandular eplithelial neoplasm called?
Papilloma
What is a benign glandular epithelial neoplasm called?
Adenoma
What is a malignant epithelial neoplasm?
Carcinoma
What is a carcinoma?
A malignant epithelial neoplasm
What is the suffix for malignant connective tissue neoplasms?
Sarcoma
What is a benign neoplasm of adipocytes?
Lipoma
What is a benign neoplasm of adipocytes?
Lipoma
What is a benign neoplasm of Cartilage?
Chondroma
What is a benign neoplasm of bone
Osteoma
What is a benign neoplasm of vasculature?
Angioma
What is a benign neoplasm of striated muscle
Rhabdomyoma
What is a benign neoplasm of smooth muscle
Leiomyoma
What is a benign neoplasm of nerves
Neuroma
What is a well-differentiated tumour?
A tumour that closely resembles normal tissue.
These have a lower grade and tend to have a better prognosis.
If a neoplasm doesnt resemble normal tissue what is it said to be?
Poorly differentiated
higher grade and would carry a worse prognosis
What does the term anaplastic mean?
When the cell type of origin is unknown the tumour is anaplastic
What is a melanoma?
A malignant neoplasm of melanocytes
What is a mesothelioma?
A malignant neoplasm of mesothelial cells
What is a lymphoma?
A malignant neoplasm of lymphoid cells
What is burkitts lymphoma?
A B cell malignancy caused by EBV
What is kaposi sarcoma?
A vascular endothelial malignancy caused by Human herpes virus 8 and related to HIV
What is ewings sarcoma?
A bone malignancy
is a teratoma?
A cancer of all 3 embryonic germ layers
What is a blastoma?
A tumour of an embryo
What is the pathway of metastasis?
- Detachment from primary tumour
- Invasion of surrounding connective tissue
- Intravasation into the lumen of blood vessels
- Evasion of host defence
- Adherence to blood vessel wall
- Extravasation to a distant site
- Proliferation of cells in new site/environment
What are the different methods of spread of a metastasis?
Haematogenous - via blood
Lymphatic - secondary formation in the lymph nodes
Transcoelomic - via exudative fluid accumulation across a body cavity. spread through pleural, pericardial and peritoneal effusions.
along nerves
Iatrogenic
What are the characteristics of a neoplastic cell?
Autocrine growth stimulation - overexpression of GF and mutations of tumour suppressor genes (p53)
Evasion of apoptosis
Telomerase - prevents telomeres shortening with each replication
Sustained angiogenesis - provides nutritional support.
What cancers commonly spread to bone?
BLT KP
Bladder
Lung
Thyroid
Kidney
Prostate
What is a neoplasm in situ?
When a neoplasm has proliferated but has not broken through the basement membrane to other tissues
When is a cancer considered to be invasive?
When it has breached its own tissue type into another area
What is a micro-invasive carcinoma?
A carcinoma that has only just broken through the basement membrane
What is invasion of a cancer dependent on?
Decreased cellular adhesion
abnormal increased cellular motility
Production of lytic enzymes to breakdown surrounding tissue
Define metastasis
The process by which a malignant neoplasm spreads from its primary site to produce secondary neoplasms at distant sites.
How do tumours invade surrounding tissues?
Proteases break down tissue surrounding neoplasm
tumour cell derived motility factors allow it to invade
How do tumours enter and exit blood vessels
(intravasion)
Collagenases break down the blood vessel wall and allow the neoplasm to enter
Adhesion receptors allow the tumour to stick to a specific area. collagenases again break the BV wall so the tumour can exit
How do neoplasms evade host defenses?
Aggregation with platelets
Shedding of surface antigens
Adhesion to other tumour cells
Why do malignant tumours often have a necrotic centre?
If neoplasms become too big and are too fast growing then they will outgrow the blood supply and so the centre of the tumour does not get enough nutrition and hence it will necrose.
What are some angiogenesis inhibitors?
Angiostatin
Endostatin
Vasculostatin
Describe the process for metastasis to the lung?
- If the carcinoma enters the venous system, it will travel through the blood vessels to the vena cava, right atrium, right ventricle and onto the pulmonary circulation
- From there, as the lung blood vessels act as a sieve, it will get stuck at some point (same process as thrombosis)
- If this new neoplasm site then grows into the venous system of the pulmonary circulation, it can travel anywhere in the body
Describe the process for metastasis to the liver?
- Liver receives 100% of blood from colorectal (remember first pass metabolism)
- Neoplasm may break off from digestive system and travel in the blood stream to the liver through the portal venous system
- Again, the liver blood vessels act as a sieve as they go down to capillary level
- Neoplasm will imbed at some point in the vasculature tree.
What cancers are screened for in the UK?
Cervical
Breast
Colorectal
Eosinophillic granulomas would be an indication of what?
Parasitic infection
What clotting facotrs make up the intrinsic, extrinsic and common coagulation cascade?
Intrinsic - 12, 11, 9, 8
Extrinsic - 3, 7
Common - 10 , 5, 2, 1
What cells are polymorphonuclear leukocytes?
Neutrophils
Eosinophils
Basophils
What cells are the mononuclear leukocytes?
Monocytes
T cells
B cells
Where is complement secreted from?
The liver
What are the 3 modes of action for complement?
Direct lysis - MAC
Chemotaxis - attract more leukocytes
Opsonisation - coat invading organisms
How can antibodies circulate in the blood
Bound to B cells
Free in plasma
Which part of the strucutre of an antibody is responsible for antigen binding?
FAB regions
Variable in sequence
Bind to specific antigens
What part of the structure of an antibody is responsible for antigen elimination?
Fc region
Constant sequence
binds to complement, Fc receptors on phagocytes or NK cells
What are the 5 classes of antibodies?
IgG
IgM
IgA
IgE
IgD
What is the structure, where it is found and its function for the IgG class of antibody?
Monomer - 2 heavy and 2 light chains
Most abundant in serum and tissues
Main Ab involved in adaptive immune response for secondary and memory responses.
Can cross the placenta
What is the structure, where it is found and its function for the IgM class of antibody?
Pentamer - dependent on J chain
Mainly found in the blood as they are too big to cross the vascular endothelium
Initial contact with Ag for immune response
High affinity low specificity Ab
What is the structure, where it is found and its function for the IgA class of antibody?
Dimer
Found at mucosal surfaces (secretory Ig)
also found in serum
Most abundant antibody in the total body
First line of defence
What is the structure, where it is found and its function for the IgE class of antibody?
50% found in blood. the rest bound to mast cells or basophils
Responsible for hypersenitivity reactions and anaphylaxis.
Important in parasitic infections
What is the structure, where it is found and its function for the IgD class of antibody?
Found on mature B cells
No effector functions identified
What are the different mechanisms of action of antibodies?
Agglutination - bind together in a clump
Neutralisation - antibodies cover the toxic sites of Ag to stop it binding
Lysis - Some antibodies can attack the cell membrane directly to rupture it.
Activate the classical complement pathway
What are cytokines?
Proteins secreted by immune and non-immune cells
What do interferons do?
Induce a state of viral resistance in uninfected cells and limit the spread of viral infection
What are the 3 types of interferons and which cells secrete them?
IFN alpha and beta
produced by virus-infected cells
IFN gamma
Produced by activated Th1 cells and this activates Macrophages
What do interleukins do?
Can be proinflammatory or anti-inflammatory
Cause cells to divide, differentiate and secrete factors
What do colony stimulating factors do?
Direct the division and differentiation of bone marrow stem cells
what do tumour necrosis factors do?
TNF alpha and beta
Mediate inflammation and cytotoxic reactions
What are chemokines?
proteins that direct the movement of cells from the blood stream to the tissues.
What is a foam cell?
Where a macrophage has phagocytosed LDL
What is innate immunity
Primitive
non-specific
rapid response
no memory is used or produced
Typically involves neutrophils and macrophages and complement activation along with physical and chemical barriers
What physical and chemical barriers are involved in the innate immune response
Physical barriers - skin, mucus, cilia
Chemical barriers - lysozymes in tears, stomach acid
What are pattern recognition receptors?
Receptors on immune cells that detect the presence of PAMPs
PAMPS and DAMPS?
Pattern-associated molecular patterns
Damage associated molecular patterns
What are Toll-like receptors?
A type of PRR that recognise structurally conserved molecules derived from microbes.
What components make up the innate immunity?
Physical and chemical barriers
Phagocytic cells -neutrophils, macrophages
Blood proteins - complement, acute phase proteins.
How can physical barriers be breached for allowing pathogens to entre the body?
Tissue trauma
Infection
What are the steps to the whole inflammatory response?
- Bleeding - acts to flush bacteria out of the site
- Coagulation - plugs the site to stop further antigens entering the system
- Acute inflammation - leukocyte recruitment
- Kill pathogens, neutralise toxins, limit pathogen spread
- Phagocytosis - clear debris
- Proliferation of cells to repair damage
- Remove thrombus - remodel extracellular matrix
- Re-establish normal function/structure of the tissue
What are 3 features of inflammation?
Increased blood supply
Increased Vascular permeability
Increased leukocyte extravasation
What cells detect presence of antigens in the blood?
Monocytes
neutrophils
What cells detect the presence of antigens in the tissues?
Macrophages
DCs
What are the 3 activation pathways for the complement system?
Classical - antibody binds to microbe
Alternative - C’ binds to microbe
Lectin - activated by mannose-binding lectin bound to a microbe.
What are the 3 mechanisms of action of complement?
Direct lysis - Membrane attack complex (MAC)
Chemotaxis - C3a and C5a
Opsonisation - coat microbes to make them easier to phagocytose (C3b)
Describe the process of Extravasation of neutrophils in acute inflammation
- E-selectin (an adhesion molecule on the capillary endothelium), is activated by IL-1 and TNF-α from damaged cells and binds to the glycoprotein CD15 on neutrophils in blood.
- This causes neutrophils in the blood to slow down and roll along the endothelium lining.
- ICAM-1 on endothelium (induced by LPS, IL-1, TNF-α) binds to integrin on neutrophil; the neutrophil stops.
- Diapedesis: neutrophil squeezes through endothelium (holes caused by C3a, C5a, chemokines, histamines, prostaglandins, leukotrienes (causing smooth muscle contractions in the bronchioles))
What are 3 ways phagocytosis can be initiated?
Antibodies bound to antigens on microbes
C3b opsonised on microbes binds to complement receptor
Mannose receptor binds to carbohydrates on bacterial wall
What are the main steps in phagocytosis?
Binding
Engulfment (phagosome)
Phagolysosome
bacterial killing
clear debris
What are the 2 pathways that neutrophils and macrophages use to kill microbes?
Oxygen dependent
Oxygen independent
What is oxygen dependent killing of microbes?
Uses ROI (reactive oxygen intermediates)
Superoxide ions are converted to H2O2 and then to a hydroxide free radical
What is the oxygen independent mechanism of killing microbes?
Enzymes - lysozymes
proteins - defensins
pH
TNF
What are the 3 outcomes of phagocytosis?
Debris gets secreted by the phagocytic cell
cell components are converted to energy
Antigens are presented on cell surface via MHC II
What cells are APCs (antigen presenting cells)?
Dendritic cells
Macrophages
B cells
What is the function of a neutrophil?
70% of all WBC
key mediator of acute inflammation
Follow chemotaxic gradients of IL-8 (CXCL8)
Will eat and kill microbes
What is the function of macrophages?
Activated by IFN-y from Th1
Will phagocytes microbes and debris to remove them.
Secrete TNF-a, IL-1 and IL-2
Can act as APCs
Can either be circulating or resident to tissues
What is the function of eosinophils?
Contain MBP
Often in response to a parasitic infection.
What is the function of Basophils and mast cells?
IgE binding and upon re-exposure IgE crosslinking via FceR1
Degranulate to release histamine in Type 1 hypersensitivity reactions,
Mast cells are fixed at tissues
Basophils circulate in the blood.
What is the function of a natural killer cell?
NKs cells are a key role in viral cell killing
CD16 Fc receptors
When activated they release perforin to kill infected cells or malignant cells.
What is the function of a dendritic cell?
These cells act as APCs and provide an interface between the innate and adaptive immune system.
What are the 3 conditions that must be met to enable antigen presenting to function?
Primary receptor binding
co-stimulation molecules
Cytokine release
What does TLR 1 detect?
Gram positive bacteria
What does TLR 2 detect?
Gram positive bacteria such as lipopeptides, lipoteichoic acid
What does TLR 3 detect?
Endogenous viral infection and tissue necrosis
Responds to ds RNA
What does TLR 4 detect?
Gram Netagive Bacteria
detects endotoxin such as LPS
What does TLR 5 detect?
Flagellin
What does TLR 7 detect?
Single stranded RNA
What does TLR 8 detect?
Viral and bacterial pathogens
Important for detecting pyogenic bacteria
What does TLR 9 detect?
Non-methylated DNA
What is the adaptive immune response?
Specific and slower response
Needs to be activated first but then the second exposure has a much larger response
Provides immunological memory
Killing is usually antibody-mediated
Involves T and B lymphocytes.
Why do we need an adaptive immune response?
Microbes can evade innate immune responses
Intracellular viruses and bacteria hide from the innate immune system
Memory to specific antigens allows a faster response upon subsequent exposure to clear infection more effectively.
Which part of the adaptive immune system deals with intracellular and extracellular microbe
B cell (humoral - antibody) - extracellular
T cell (cell-mediated) - Intracellular
To recognise self from non-self what is required?
MHC proteins
What do T lymphocytes respond to?
Intracellular presented antigens
Where do T cells mature?
In the thymus
Where do B cells mature?
In the bone marrow
What is Thymic central tolerance?
Where T cells are tested to see if they recognise self antigens . if they produce an immune response they they are selected against and killed by T regulatory (Treg) cells
Where is MHC I found?
On all nucleated cells
Where is MHC II found?
On APCs Only
For intrinsic antigens (i.e. virus): which MHC class presents them, where is the MHC expressed, which T cells bind, what is the function of this T cell?
- MHC Class I
- All cells express MHC Class I (except for red blood cells) (everyone expresses MHC Class one
- Tcytotoxic (CD8) cells
- Kill infected cell with intracellular pathogen directly
For extrinsic pathogens (i.e. extracellular pathogen): which MHC class presents them, where is the MHC expressed, which T cells bind, what is the function of this T cell?
- MHC Class II
- Only antigen presenting cells express MHC Class II
- Th (CD4) cells
- Help B cells make antibodies to extracellular pathogen and can help directly kill pathogen
What is required for full T cell activation?
Co-stimulatory molecules CD28 on the T cell binds to CD80/CD86 on the APC to fully activate the T cell
What is secreted from an activated T cell?
IL2
binds to the T cell receptor (autocrine)
What does T cell activation lead to?
Division
Differentiation (to CD4 or CD8)
Effector functions
Memory
What determines whether a T cell will differentiate into a Th1 or Th2 CD4 T cell?
Levels of IL-12
High IL-12 = Th1
Low IL-12 = Th2
What is the function of a Th1 CD4 T cell?
Travel to secondary lymphoid tissue
Secrete IFN gamma to help kill intracellular antigens
What is the function of a Th2 CD4 T-cell?
Binds to a B cell presenting an antigen and stimulates B cell divide (clonal expansion) and differentiation
Secretes IL-4 to stimulate differentiation
What is the function of a Cytotoxic CD8 T cell?
Kills cell directly.
Formation of perforin and granulysin which induce apoptosis in infected cells,
Secrete IFN gamma to inhibit viral invasion of neighboring cells to prevent viral spread
Secretion of chemokines to recruit more immune cells.
Express Fas-ligand to initiate apoptosis
Which membrane bound antibodies do B cells Express?
IgM or IgD monomers
How many types of antibodies can an individual B cell make?
1 Antibody specific to 1 antigen.
What happens if a B cell recognises self?
The B cell is killed in the bone marrow
How do B cells act as APCs?
Phagocytose the pathogen
Present the epitope on MHC II
Tcell binds to MHC II
lots of costimulatory molecules required such as CD80 and CD86
How is a B cell activated?
Th2 T cell binds to antigen presented via MHC class II
Co-stimulatory molecules bind CD80/CD86
T cell releases IL-4 and IL6
IL-4 induces B cell proliferation (clonal expansion)
IL-6 induces B cell differentiation into a plasma cell or memory cell
What is B cell somatic hypermutation?
A cellular mechanism where the immune system adapts to new foreign elements that confront it