2. Methods of Disease Flashcards
What are the 3 types of cell injury?
Reversible cell injury = the cell can return to full function once the cause of injury is stopped e.g. hypoxia, radiation, drugs
Irreversible cell injury = If the injury is prolonged, then the cell will die.
Ischaemic/reperfusion injury = cells that have been oxygen deprived (ischaemic) are damaged even more when blood supply resumes (reperfusion).
What is necrosis?
Unregulated cell death.
severe cell swelling followed by rupture.
What is apoptosis?
Programmed cell death.
What is oncosis?
A series of reactions after cell injury which leads to its death.
(NOT the same pathway as apoptosis)
How can oxygen derived free radicals cause cell injury?
They bind to the lipid membrane of a cell and destroy it.
What type of cell injury has these characteristics?
Mitochondrial swelling, lysosome swelling, membrane damage, leakage of enzymes
Irreversible cell injury
What type of cell injury has these characteristics?
Cell swelling, pallor, hydropic change (water build up), vacuolar degeneration
Reversible cell injury
What causes cellular swelling in reversible cell injury?
Na+ build up due to a lack of ATP (only glycolysis occurs).
This causes water to move in by osmosis.
In irreversible cell injury, there is membrane damage to lysosomes, cell membrane and mitochondria.
How does damage to these lead to cell death?
Lysosome - lysozyme enzymes leak and degrade cell.
Cell membrane - calcium ions flood the cell which activate Caspaces (pathways leading to apoptosis) and other enzymes which degrade the cell.
Mitochondria = Cyt C leaks which activates Caspaces.
Autophagy is when your body recycles its cells as a source of nutrients and energy.
Does this process induce an inflammatory response?
No
What are the main differences between necrosis and apoptosis?
Necrosis =
- Unregulated / ‘accidental’
- Affects large areas of cells in clumps
- Cells swell, rupture and spill contents
- Inflammation
Apoptosis =
- Programmed
- Affects specific cells in different areas
- Cells shrink and form apoptotic bodies which are phagocytosed
- No inflammation
What is the most common form of necrosis?
Coagulative necrosis.
Occurs in most organs but mainly in myocardium
What is liquefactive necrosis and where is it seen?
Tissue turns to liquid.
Seen in the brain.
What does gangrenous necrosis look like and what is its main cause?
Tissue rots into a black colour, usually on hands and feet.
(3 types - wet, dry, gas).
Mainly caused by infection.
What does caseous necrosis look like and what is its main cause?
Structureless dead pink tissue.
Mainly caused by tuberculosis (you can actually see the this as dark bits inside the cells on a microscope as the tuberculosis cant be destroyed).
What does fat necrosis look like and what causes it?
Loss of cell structure, looks white due to lots of vacuoles.
Caused by trauma to fatty area or enzyme action.
What does fibrinoid necrosis look like and where does it occur?
It is seen in what 2 conditions?
Occurs in blood vessels.
The wall of the artery is bright pink.
Seen in malignant hypertension and autoimmune diseases.
What is neoplasia?
Abnormal and excessive tissue growth
What do these prefixes mean? Ana- Dys- Hyper- Hypo- Meta-
Ana = Absence (anaplasia) Dys = Disordered (dysplasia) Hyper = Excess (hyperthyroidism) Hypo = Deficiency (hypothyroidism) Meta = Change from one state to another (metaplasia)
What do these suffixes mean?
- itis
- oma
- osis
- oid
- penia
- itis = Inflammatory process (appendicitis)
- oma = Tumour (carcinoma)
- osis = State / Condition (osteoarthrosis)
- oid = Bearing a resemblance to (rheumatoid disease)
- penia = Lack of (thrombocytopenia)
What do these suffixes mean?
- cytosis
- ectasis
- plasia
- opathy
- cytosis = Increased number of cells (leukocytosis)
- ectasis = Dilation (bronchiectasis)
- plasia = Disorder of growth (hyperplasia)
- opathy = Abnormal state lacking specific characteristics (lymphadenopathy)
What does ‘sequela’ mean?
A condition which is a consequence of a previous disease/injury
What is the difference between ‘aetiology’ and ‘pathogenesis’?
Aetiology = cause of disease Pathogenesis = progression of disease
What is ‘epidemiology’?
Distribution of disease in a population
Identify the two main components of the immune system.
Adaptive immunity
Innate immunity
What is the single biggest preventable risk factor for autoimmune disease?
Smoking
Women have a stronger immune system than men, but are more susceptible to autoimmune diseases.
Why is this?
Women have two X chromosomes, therefore double the genes.
Resulting in a more potent immune response than men.
Which of these are responsible for inflammatory cytokine production?
- Autoreactive B cells
- Autoantibodies
- Autoreactive T cells
Autoreactive T cells
Any cell in the body can be subject to an autoimmune response.
True or False?
TRUE
What is the difference between ‘organ specific’ and ‘systemic’ autoimmune diseases?
Organ specific = Affects a single organ
e.g. autoimmune thyroid disease
Systemic = Affects several organs simultaneously
e.g. Connective tissue diseases
What is Hashimoto’s thyroiditis?
Autoimmune disease which gradually destroys the thyroid, leading to hypothyroidism
What is Grave’s disease?
Autoimmune disease where autoantibodies bind to TSH receptors, overstimulating them and leading to hyperthyroidism
What autoimmune disease is associated with ‘butterfly rash’?
Systemic lupus erythematosus (SLE)
or more simply…
Lupus
Immune complexes are more likely to cause problems where circulation is slow and there is a rich capillary network.
Why?
Greater chance of precipitating out and causing local inflammation.
Which of these is not a connective tissue disease?
- Systemic lupus erythematosus
- Scleroderma
- Hashimoto’s thyroiditis
- Polymyositis
- Sjogren’s syndrome
Hashimoto’s thyroiditis
What is the main advantage of testing for autoantibodies in diagnosis?
Early diagnosis.
You can detect autoantibodies years before someone develops an autoimmune disease.
What is immunosuppression?
A natural/artificial process of switching off the immune response partially or fully.
Can be accidental or on purpose.
Can result in immunodeficiency - susceptible to infections
What is the difference between primary and secondary immunodeficiency?
Give examples.
Primary = genetic (rare)
child who keeps getting infection suggests an immunological problem
Secondary = acquired (much more common)
e.g. transient, stress, surgery, malnutrition, drugs, infection
What is Severe Combined Immunodeficiency (SCID) a result of and how is it treated?
Defective T cells and B cells.
Bone marrow transplant
Gene therapy
Define allergy.
A damaging immune response by the body to a substance it has become hypersensitive to
What is the function of dendritic cells?
Engulf cells and present protein antigens on their cell surface.
What are antibodies?
Proteins produced by the body which identify and neutralise foreign objects.
What are macrophages?
Large phagocytes which engulf and destroy pathogens/apoptotic cells.
What is the immunopathogenesis for Type 1 hypersensitivity (how does the immune system respond)?
What are its clinical features?
Mast cells and basophils are degranulated when antigens bind to IgE antibodies on their cell surface, forming crosslinks.
Preformed inflammatory chemicals are released (histamine, proteases, prostaglandin, leukotrienes).
Clinical features:
- Fast onset (15-30mins)
- Wheal and flare
Identify 4 symptoms of allergy.
- Increased heart rate
- Swelling + inflammation
- Blood clots
- Bronchoconstriction
- Blood vessels dilate
- Increased permeability of capillaries
- Gastric acid secretion
- Adrenaline release
What is anaphylaxis?
An acute life-threatening, IgE mediated systemic hypersensitivity reaction.
(severe allergic reaction)
Identify 4 clinical symptoms of anaphylaxis.
- Swelling of tongue/neck
- Low pressure
- Difficulty breathing
- Dizziness, loss of consciousness
- Urticaria and angioedema
- Severe abdominal pain, vomiting, diarrhoea
How are we sensitised to an allergen (immunopathologically)?
- Dendritic cell presents the allergen to a naïve T cell.
- This differentiates and activates naïve B cells.
- Memory B cells with specific IgE for the allergen are formed which recognise the allergen on re-exposure.
What does the ‘Dual allergen exposure hypothesis’ suggest about allergic sensitisation and allergen tolerance?
Early exposure to a food protein through a disrupted skin barrier e.g. eczema leads to allergic sensitisation.
Early oral exposure (eating) to food allergen induces tolerance (less likely to be allergic).
Allergic responses are inherited conditions.
True or False?
FALSE
you might be more susceptible to an allergy, but you don’t inherit it.
What are the 2 most common food allergies in children?
- Milk
2 Egg
Food allergies are more common in adults than children.
True or False?
FALSE
How are allergies diagnosed?
Skin prick test
How is rhinitis treated?
(hay fever)
Nasal steroids + Antihistamines
Can aero-allergic stimuli such as house dust mite make asthma worse?
Yes
What is the ‘Atopic triad’?
Asthma
Rhinitis
Eczema
What is the mechanism for Type II (cytotoxic) hypersensitivity?
What are its clinical features?
Common antigen?
Diseases resulting in this hypersensitivity?
IgG/IgM antibodies bind to self or foreign antigens on the cell surface.
The target cell is then destroyed via:
1. Complement activation
2. Phagocytosis
3. ADCC (antibody dependent cell-mediated cytotoxicity)
Clinical features:
Onset = minutes - hours
Cell lysis + necrosis (damage + death)
Common antigen = penicillin
Diseases:
- Goodpasture’s nephritis
- Blood transfusion reaction
In a blood transfusion, what happens if incorrectly matched blood is given to a patient?
Type II hypersensitivity reaction.
- Patient’s antigen presenting cells detect and display foreign antigens to B cells to produce antibodies.
- Complement is activated and a MAC attack complex is formed which makes a hole in the cell and kills it.
The classic pathway of Complement is triggered by bacteria.
True or False?
FALSE
Bacteria trigger alternative pathway.
Immune complexes e.g. IgM, IgG, MBL trigger classical pathway.
What is the mechanism for Type III hypersensitivity?
What are the clinical features?
Traditional caused by?
Disease with this hypersensitivity?
IgG/IgM antibodies bind to SOLUBLE antigens, forming immune complexes which deposit onto tissue (e.g. endothelium of blood vessel wall).
Complement is activated which then damages/destroys these tissues.
Clinical features:
Onset = 3-8hours
Vasculitis (inflammation of blood vessels)
Serum sickness (allergic reaction to an injection)
Disease: SLE (lupus)
In a blood test, which components of Complement are unusually low in SLE (lupus)?
C3 + C4
What type of hypersensitivity reaction is associated with vasculitis?
Which parts of the body are particularly susceptible to this?
Type III
Activation of Complement leads to damage and destruction of blood vessel walls and fluid leaks out (oedema).
Kidneys + Joints + Skin
What is the mechanism for Type IV (delayed) hypersensitivity?
What are the clinical features?
What are the common antigens?
Disease associated with this hypersensitivity?
T-cell mediated cytotoxicity.
Antigen-presenting cells present a foreign body to T-cells which mediate inflammation and tissue damage.
Clinical features:
Delayed onset 48-72hours
Erythema induration (redness and hardening)
- Metals e.g. nickel
- Tuberculin test (prick skin with TB, causes reaction if previously encountered)
- Poison ivy
Disease: Contact dermatitis (inflammation of the skin due to an allergen/irritant)
Which antibody mediates Type I hypersensitivity?
IgE
What is the key difference between Type II and Type III hypersensitivity?
Type II is targets cells, Type III targets soluble antigens
SLE is an example of which type of hypersensitivity?
Type III
Which antibodies mediate Type III hypersensitivity?
IgG and IgM
Name 3 chemical mediators produced by a mast cell.
- Prostaglandins
- Histamines
- Leukotrienes
- Proteases
- Chemotactic factors
What is the first step in the healing process after an injury?
Acute inflammation
Allows immune system to enter damaged area.
Protects against infection.
What are the 2 possible healing outcomes following injury and how do they differ?
- Regeneration =
Cells regrow and tissue is restored to normal structure and specialised function. - Repair =
Cells cannot regrow so a scar is formed instead, loss of specialised function.
What are the 3 characteristics of ‘Labile cell populations’?
Give an example.
- High cell turnover
- Active stem cell population
- Excellent regenerative capacity
Epithelia (e.g. in skin + gut)
What are the characteristics of ‘Stable (quiescent) cell populations’?
Give an example.
- Low normal cell turnover HOWEVER this turnover can increase massively if needed
- Good regenerative capacity
Liver, renal tubules
What are the characteristics of ‘Permanent cell populations’?
Give an example.
- No physiological turnover (cant be replaced once they die)
- Long life cells
- No regenerative capacity
Neurons, striated muscle (e.g. heart muscle)
Labile cells and stable cells continuously go through the cell cycle.
True or False?
FALSE.
Only labile cells continuously go through the cycle.
Stable cells leave the cell cycle and re-enter it depending on need.
(permanent cells do not undergo cell cycle at all)
The liver and renal tubules are examples of which type of cell population?
Stable (quiescent)
Neurones in the brain and cardiac muscle are examples of which type of cell population?
Permanent