Immune System Flashcards
what is the purpose of the immune system
to protect organisms against harmful pathgens or in response to other physical attacks in a nuber of ways
3 lines of defence
physical
general cellular/protein
specific/targeted
3 broad phases which are from convergent or parallel evolution in different species
recognition phase
activating phase
effector phase
recognition phase
has to be able to tell the difference between self and non-self
pattern recognition receptors on the surface of cells detect the general feature so fgroups of micro-organisms and pthogens (Microbe associaed molecular patterns, or pathogen associated molecular patterns)
patterns are specific to the microorganisms and are different to the host, and can be used to recognise non-self cells
activating phase
mobilisation of cells and molecules to fight an invader
binding of Microbe associated molecular patterns to pattern recognition proteins causes the activation of this phase
can include:
defensins (antimicrobial peptides)
cytokine signal production, resulting in further immune responses
effector phase
mobilised cells or molecules destroy the invading microorganisms
defensins disrupt pathogen membranes leading to cell deth
macrophages
destroy pathogens through phagocytosis
also causes regulated cell death
how to macrophages work?
destroy pathogens through phagocytosis
engulf pathogens and encase it in a vacuole
lysosomes fuse with the vacuole and digest the bacterium
the antigens from the bacterium are presented on teh cell surface
T cells can use antigens to further fight infection
How does regulated cell death occur?
disruption of membranes and lysis of the cell itself
examples found in fungi
apoptosis-like death (apoptosis bodies)
heterokaryon incompatability-induced death (membrane disruption)
ferroptosis (lipid peroxidation)
what is the innate immune system
first line of defence
skin and associated mucus
physical and chemical barriers
all organisms have an innate immune ststem
it is quick
it is indescriminate
second line of defence?
when the first line is corrupted, the second line kicks in
macrophages and mast cells mount an inflammatory response to prevent infection
third line of defence
adaptive
lymphocytes destroy the infectious agents themselves or through circulating antibodies
in order for this to occur, it must have previously encountered the pathogen, forming a memory to produce a stronger attack
what is acquired immunity
higher order animals like mammals
lacking in plants
more targeted
slower
replication of specific immune cells which act as memory in case the pathogen is reincountered
What is inflammation?
second line of defence
non-specific but effective
isolates the damaged area to stop the spread of damage
recruits molecules and cells to promote the destruction of the damage and promote healing
it is lead by mast cells in invertebrates
- secretes cytokines to activate immune cells
- increase of blood flow and permeability of blood cells
- blood clotting
Plants innate defenses
structural defences
- epidermis
- thorns
- hairs
- chemicals to deter plant eating animals
membrane bound receptors recognise molecular patterns that signal pathogen prescence
triggers a signalling cascade, triggering the immune response including
- closing of the stomata
- strengthening of the cell wall
- secretion of antimicrobial agents
what is the hypersensitive response?
some pathogens try to overcome the plants innate immune system, and plants have developed resistance proteins that detect effector proteins
these proteins trigger another cascade that results in the expression of pathogenesis genes that trigger the hypersensitive response
- rapid programmed cell death
- rapidly limits the spread of the pathogen by reinforcing the cell walls of other cells and systemic acquired resistance
what is systemic acquired resistance?
long term resistance for parts of the plants that are removed from the initial site of infection
what is teh adaptive cell-mediated response?
innate immune system actives the adaptive immune system
phagoytic cells of the innate immune system such as macrophages and dendritic cells
major histocompatability complex (MHC) proteins bind to the antigens of foreign bodies and protrude from the phagocyte
the MHC-antigen complex activates cells of the adaptive immune system
T cells as the cell mediated immune response
main cellular response of the adaptive immune ststem
only set into action by single specific antigen
memory T cells will only activate when this particular antigen is reencountered
the more antigens an organism encounters in its life, the larger its arsenal of T cells
A type of WBC
rapidly multiples to produce specialised cells
what is cell mediated immunity
adapted cellular response to prevent infection
How to antigen presenting cells work?
macrophages engulf and digest harmful pathogens through phagocytosis
the pathogen antigen is fragmented by a phagolysosome and transported to the macrophages surface
antigen is then presented on the surface
major histocompatability class moelcule embed the fragments for presentation on teh surface on APC
these can then be detected by T cells
helper t cells
secrete chemicals to stimulate growth and differentiation of cytotoxic t cells
cytotoxic t cells
kills damaged cells
memory t cells
remsin in the host after the infection is cleared, just in case there is reinfection
suppressor t cells
inhibit the immune ststem to prevent further destruction to the host tissues
what is the adaptive humoral immune response?
also known as antibody-mediated immune response
targets pathogens circulating in the ‘humors’ or extracellular fluids, such as blood and lymph
antibodies target invading pathogens for destruction
what are the 3 ways antibodies target invading pathogens
neutralisation
opsonisation
activation of the complement system
neutralisation
antibodies neutralise a pathogen by interfering with its ability to infect host cells
not able to bond to host cells and enter etc.
opsonisation
antibodies function as opsonins, which tag pathogens for destruction
the formation of the antigen antibody complex attracts and stimulates phagocytic cells that engulf and destroy the pathogen
complement cascade
sequential cascade of more then 30 proteins
proteins opsonise pathogens for destruction of macrophages and neutrophils, induce the inflammatory response with the recruitment of immune cells and promote lysis of the pethogen
