Immunity Flashcards
How does the skin provide a physical defence against pathogens?
Sweat glands and sebaceous glands secrete fatty acids which inhibit bacteria growing on the skin
What is the role of the mucociliary escalator?
Provides a physical defence against pathogens entering the lungs
Explain the defence provided by the mucociliary escalator to the lungs:
Ciliated cells ‘beat’ to push a watery saline layer of mucus towards the pharynx, on top of this watery layer is a thicker layer with dust and pathogens in.
What may damage the mucociliary escalator?
Smoking or Some general anaesthetics
What is meant by autoimmune disease?
Where the body begins to attack itself, the immune system is faulty
The immune system recognises materials as ‘self’ or ‘non-self’ and attacks the latter, what must happen to reduce the risk of attacking an organ when it has been transplanted?
Immunosuppressive medication is required
What are the main two parts of the immune system?
Innate immunity
Acquired (adoptive) immunity
What is innate immunity?
A defence present from birth, it works fast and is non-specific
What is acquired immunity?
(An acquired) defence which builds over time, it acts slowly but specifically and has memory to remember prior infections
What are the 4 cardinal signs of inflammation?
Heat
Redness
Swelling
Pain
Mast cells are attracted to sites of injury, what happens when the cells reach the injury?
They release histamine which diffuses into the blood vessels
What does histamine do when it enters the blood?
It causes vessels to dilate and therefore become ‘leaky’, this allows complement proteins to leave the vessels and attract phagocytes
Describe the process of inflammation following tissue injury:
Release of chemical mediators (histamine) Increased vasodilation (heat / redness) Increased permeability (swelling / pain) Attracted WBCs (phagocytosis)
What causes inflammation to appear red?
Histamines dilate the vessels around the damage meaning more blood flows to the area, causing it to appear redder
What causes inflammation to appear swollen?
Proteins leave the bloodstream as histamine makes vessels ‘leaky’, this decreases the pull of water into the vessels causing it to fill the space around the injury
What causes inflammation to appear hot?
Histamines dilate the vessels around the damage meaning more blood flows to the area, causing it to be hotter as blood is warmer than the outside of the body
What causes inflammation to be painful?
Pain receptors are triggered during the inflammatory response
Why is it beneficial that an inflammation is hot?
Increases the metabolic rate of cells causing quicker healing
The slowing of blood flow during inflammation allows margination and consequently diapedesis, what are these terms?
Margination - Leukocytes clinging to capillary walls
Diapedesis - Leukocytes passing through capillary walls
What is the thermoregulatory centre?
Hypothalamus
What is the body’s set temperature?
36.9 degrees celcius
What substance acts on the brain to cause a fever (elevated temperature)?
Pyrogen
Why does a fever cause people to shiver even when their temperature is higher than normal?
Pyrogen acts on the hypothalamus to alter the ‘default’ body temperature higher, so even when the temp dips below this you still feel cold and start to shiver
What are antipyretics such as paracetamol used for?
They produce cyclooxygenase (cox) which reduces the effect of pyrogen on the hypothalamus, decreasing the effects of a fever
What are the benefits of a fever (increased temperature)?
Leukocytes work better under a higher temperature
Bacteria we may want to kill are less effective
What are the costs of a fever (increased temperature)?
Brain damage can occur if temp goes above 42 degrees (rare)
Also feel unwell
What cells are involved in non-specific phagocytosis?
Macrophages
Neutrophils
Dendritic cells
Simply, what is phagocytosis
Engulfing an entire cell / pathogen etc
How does a phagocytosing cell know what to engulf?
Inside the cell there is a pattern recognition receptor (PRR) which recognises pathogen associated molecular markers (PAMP) on specific pathogens
What initiates phagocytosis?
The binding of the pattern recognition receptor (PRR) to the pathogen associated molecular markers (PAMP)
Explain the process of non-specific phagocytosis:
PRR binds to PAMP
Cytokines and cytotoxins released
Pathogen engulfed and digested
All nucleated cells contain MHC’s, what are these?
Major Histocompatibility Complex, they are specific to an individual so cells can recognise local and foreign cells
What are natural killer cells?
A non-specific type of lymphocyte which recognise cells which lack MHC’s (foreign cells)
Some viruses or cancers can cause cells to lose / alter their MHC’s, what effect can this have?
The affected cells are destroyed by apoptosis
What stops a natural killer cell from attacking any cell it comes across?
The Major Histocompatibility Complex is specific to an individual, therefore a killer cell recognises a cells which belong
Explain apoptosis:
Natural killer cells recognise a cell without a MHC and release perforins and granzymes to destroy the cell
What effect do perforins have on a cell?
Make pores in the cell membranes
What effect do granzymes have on a cell?
They digest the cell from within
Define the complement process:
A non-cellular mechanism comprising of a cascade (25) of plasma proteins
What is produced by a complement and what does it do?
A membrane attack complex (MAC) which ruptures a pathogen
What are the 5 strategies used by the innate immune system to respond to infection?
Inflammation Fever Non-specific phagocytosis Natural killer cells Complement
How many plasma proteins are involved in the complement process?
25 different proteins, all initiated by another
Where can lysozymes be found?
Tears
Saliva
Nasal secretions
Sweat
What is the function of lysozymes?
Cell lysis; the breakdown of the membrane
Where can acid secretions be found?
Sebum (in skin) Hydrochloric acid (in stomach)
What is the function of acid secretions?
Prevent microbial growth and kill microorganisms
What is the function of mucus?
Traps microorganisms (and dust) so they cannot be released
What is an interferon?
A protein produced by mast cells which interfere with virus production and infection
What chemicals are involved in innate immunity?
Surface chemicals (lysozomes, acids) Histamine Kinins Interferon Complement Prostaglandins Leukotrienes Pyrogens
What are kinins?
Proteins derived from plasma proteins, they cause vasodilation, increase permeability and stimulate pain receptors whilst attracting neutrophils
What are pyrogens?
Chemicals released by neutrophils, monocytes and other cells which stimulates fever production
What are the two categories of adaptive immunity?
Humoral (antibody-mediated)
Cell-mediated
What is responsible for the mediation of the humoral response?
B lymphocytes
What is responsible for the mediation of the cell-mediated response?
T lymphocytes
Where do B lymphocytes originate?
Bone marrow
Where do T lymphocytes originate?
Bone marrow
Where do lymphocytes mature in the humoral response?
Bone marrow
Where do lymphocytes mature in the cell-mediated response?
Thymus
What type of receptor do lymphocytes have in the humoral response?
Antibody
What type of receptor do lymphocytes have in the cell-mediated response?
T-cell receptors
What is an antigen?
A biomolecule which binds to a specific antibody to stimulate an immune response
Which type of pathogens does the humoral response fight?
Pathogens free in the bodily fluids
What is responsible for detecting a pathogen in the humoral response?
Antigens in the fluid to detect pathogens
Activation of B cell receptors results in the formation of what?
Plasma cells and memory cells
Non specific host defence that exists prior to exposure to an antigen is called what?
Innate immunity
What is the name for temperature rising chemicals?
Pyrogens
