Immune system L2 Flashcards
why do we need an immune system
protect against infection
crucial to human survival
what classes of pathogen does the immune system protect against
bacteria
viruses
fungi
parasites (protozoa, worms)
what diseases does bacteria casue
food poisoning
tuberculosis
what diseases do viruses cause
small pox
AIDS
what disease does fungi cause
thrush
ringworm
what diseases do parasites cause
malaria
sleeping sickness
what pathogens are the largest –> smallest
worms protozoa fungi bacteria viruses
what is the microbiome
microbial communities of tissues (skin, oral mucosa, gastrointestinal tract)
immune system and pathogenic vs commensals
Immune system must be able to recognise difference
whether they cause damage or not
what do commensals cause on host
cause no damage to host, can perform important functions
can become pathogens if they are in the wrong location
if the immune system has a diverse nature of pathogens what is the response
range of defence mechanisms
if the immune system has a vast range of pathogens what is the response
vast range of antigen receptors
if the immune system has a rapid growth of microbes what is the response
rapid inflammatory response
if the immune system minimises damage to host what is the response
regulatory mechanisms
why must the immune system respond quickly
- no damage to host
- immune system must have regulatory systems to control response
what is recognition in immune response to infection
locate and identify pathogen
what is defence in immune response to infection
repel or destroy pathogen
what are the cardinal features of immune system
specificity
memory - immune cells
self-discrimination – all different cells in body, what is self and what is not self
what are the levels of defence against pathogens
physicalbarriers
then innate immune system adaptive immune system
how do innate and adaptive immune responses link
feedback between the two
what happens when the pathogen penetrates physical barriers
engaged by cells and soluble factors of innate immune system
what does the skin and mucosal provide as a physical barrier
tough impenetrable barrier but when it is breached by physical damage (such as wounds or burns) it exposes soft tissue and renders them vulnerable to infection
which barriers are stronger
skin
which barrier are more vulnerable
mainly mucosal membranes
what routes of entry can infect via mucosal surfaces
airway
GI tract
reproductive tract
what routes of entry can infect via external epithelial surfaces
external surfaces
wounds and abrasions
insect bites
what must pathogens be like to be transmitted via airway
light enough to be airbourne
what are the two types of immune response
innate
adaptive
where is the innate immunity
peripheral organs
what does the innate immunity detect
infectiousagents
what does innate immunity do
- containment/elimination of infectious agent using non-specific mechanisms
- alert the acquired immune system regarding the nature of the infection
where is the adaptive immunity
lymphoid organs
then peripheral
what does the adaptive immunity do
control/eliminate infectious agent using newly generated tools, specific for the infectious agent
how does the innate immunity work
‘recognising non-self’
pathogens are foreign
presence of cell wall is foregin
what is the innate immune response
cellular involvement
e.g. phagocytosis
what are neutrophils
phagocytic cells, also classified as granulocytes as contain granules in cytoplasm
what are the granules like in neutrophils
are very toxic to bacteria and fungi, and cause them to stop proliferating or die on contact
what aremacrophages
efficient phagocytic cells
what do macrophages do
ability to roam outside of the circulatory system is important, because it allows macrophages to hunt pathogens with less limits
macrophages can also release cytokines in order to signal and recruit other cells to an area with pathogens
what are mast cells function
the activation of these cells by complement, which causes the mast cells to degranulate, and leads to the release of inflammatory mediators such as histimine
what happens in the recognition process for innate immunity
bacterial cell surface induces cleavage and activation of complement
complement covalently bonds to bacterium, other attracts effector
complement receptor on effector cell binds to complement fragment on bacterium
effector cell engulfs bacterium kills it
what happens in the innate immune recognition
pattern recognition receptors contain toll like receptors
TLRs, some on the surface, some inside
viruses quite often invade straight into cells, need substance inside cell to detect it to defend against
PRRs recognize pathogen associated molecular patterns (on bacteria surface)
how many pattern recognition receptors are there
several receptors expressed by the same cell
what is the structure of pattern recognition receptors
multiple domain structures
broad binding specificity
where are the pattern recognition receptors present
plasma membrane, endosomes and cytosol
what response is caused at pattern recognition receptors
Immediate response
what is involved in adaptive immunity
T lymphocytes
B lymphocytes
what do T lymphocytes express
T cell receptors
what do T lymphocytes do
interact with other cells
can kill cells, or facilitate immune responses by other cells
where are the T cells generated
thymus
where are the B cells generated
bone marrow
what cells are linked to the T lymphocytes
Killer T cells (CD8+), Helper T cells and regulatory T cells (CD4+)
what do B lymphocytes do
make antibodies (immunoglobulins)-cell surface and secreted
Can improve the antibodies made over time
protection against extracellular pathogens & toxins
how many specificity is there per receptor of cell
one specificity
what happens when the B cell receptor antigen binds
resembles antibody attached to cell surface
specific ligand, mediates the activation of the B cell
where are lymphocytes generated
primary lymphoid organs
what is in the primary lymphoid organs
bone marrow
thymus
what happens in secondary lymphoid organs
mature naïve lymphocytes are maintained and adaptive immune response initiated
what is in the secondary lymphoid organs
lymph nodes, tonsils, spleen, Peyer’s patches, mucosa associate lymphoid tissue (MALT)
what do lymphocytes do
circulate in the blood and lymph
where are lymphocytes found
found in large numbers in lymphoid tissue or organs
which cells are innate immunity
neutrophil
eosinophil
basophil
monocyte
which cells are both innate and adaptive immunity
dendritic
which cells are adaptive immunity
B cells
T cells
how long is the innate response
rapid (hours)
how long is the adaptive immunity response
slow (days to weeks)
what is the innate immune response like
fixed
what is the adaptive immune response like
variable
what is the specificities of the innate immune response
limited number
what is the specificities of the adaptive immune response
numerous, highly selective
what is the innate immune response like during
constant
what is the adaptive immune response like during
improve during response
what are the stages of an immune response - innate (immediate 0-4hrs)
infection
recognition by non-specific effectors
remove infectious agent
what are the stages of an immune response - early induced (early 4-96hrs)
infection
recognition by non-specific effectors
inflammation recruitment and effector cell activation
remove infectious agent
what are the stages of an immune response - adaptive (late > 96hrs)
infection transport of antigen to lymphoid organs recognition by naive B an T cells clonal expression and differentiation to effector cells remove infectious agent
why do vaccines work
due to immunological memory
what does yersinia pseudotuberculosis cause
mimics acute appendicitis
what does Yersinia pseudotuberculosis
do
interact with immune system is very different
