innate immune response Flashcards
what are barriers to pathogens
anatomical and chemical barriers;
e.g skin, IgA in secretions, stomach acid
intrinsic immunity:
apoptosis of infected cell
innate immunity+ acquired immunity
describe innate immune response
rapid initial response, it is nonspecific (responds to many different pathogens)
uses phagocytes, NK cells, interferons, antimicrobial peptides
causes acute inflammatory response
function is phagocytosis, infalmmation and cytotoxicity
what is involved in intrinsic immune response
always present in uninfected cells
processes such as apoptosis, autophagy, RNA silencing and antiviral proteins
what is first line of defence against viral pathogens
cellular proteins that inhibit viral replication, cells without viral restriction factors are more permissive to viruses
what are soluble factors of innate immunity
antimicrobial enzymes ( lysozyme)
antimicrobial proteins (defensins, histatins, cathelicidins)
complement, cytokines and acute phase proteins
what are defensins
kill bacteria, fungi and some viruses
they are small cationic antimicrobial peptides which form ion channels on microbes thus disrupting ion concentration
widely expressed, 2 main families; alpha defensins and beta defensins
alpha defensins are constitutively expressed
some beta are constitutive some are induced
what are pattern recognition receptors
receptors which recognise the differences between pathogenic agents from self antigens and environmental antigens
they recognise associated molecular patterns (PAMPs) and host damage associated molecular patterns (DAMPs)
PPRs are located on the cell surface and in cytoplasm, they are also secreted
each protein is individually encoded and there is low polymorphism
each individual will have between 10s-100s of PPRs
what is MHC
major histocompatability complex, located on cell surface, each MHC variant can bind and recognise different peptide sequences
there are 12 classical MHCs, each protein is individually encoded and very polymorphic
what are TCRs
t cell receptors, located on cell surface
recognise highly specific peptide-MHC complexes
millions of TCRs in an individual
genetic recombination creates diversity in these
where are antibodies found
on cell surface and secreted, highly specific to antigens for recognition
genetic recombination creates diversity
what intracellular receptors recognise pathogens
in cytosol there are:
NOD like receptors which recognise peptidoglycans
RIG-1 like receptors recognise viruses by recognising certain single stranded RNA patterns
c-GAS recognises pathogenic DNA
all of these are PRRs
what are toll like receptors
toll like receptors, are common family of PRRs, expressed on plasma membrane or endosomes/phagosomes
after ligand engages toll like receptors it causes the association of protein kinases and adaptor proteins which cause activation of transcription factors which cause effectors to activate, cytokines and chemokines are produced in response to TLR activation which can cause more effectors to activate
what are effects of macrophages and DCs in adaptive immunity
they act as antigen presenting cells, helps develop adaptive immunity
what are the cells of innate immunity
macrophages, dendritic cells, granulocytes (neutrophils, basophils and eosinophils), mast cells and natural killer cells
what happens in process of phagocytosis
in phagocytosis the following happens; the cell detects a pathogen via chemotaxis, it adheres to pathogen via PAMP recognition, the cell is activated via pattern recognition receptor which initiates phagocytosis. Degredation products are then released which leads to bacterial killing and digestion. Phagolysosomes then form which then cause a phagosome to form.
what is opsonisation
antibodies and complement help with phagocytosis. Once the microbe is covered with antibodies or complement it increases chemotaxis and vascular permeability. This process is called opsonization
what is process of respiratory burst
respiratory burst causes oxygen dependent killing
enzyme called NADPH oxidase, as the phagolysosome forms it activates this enzymes which promotes oxygen uptake which causes respiratory burst. Which forms hydrogen peroxide which kills bacteria, and reactive oxygen species. Reactive nitrogen species are also formed which kills.
what are the first cells to respond to infection
neutrophils, they have rapid migration from blood to infected tissues but are short lived
what are natural killer cells
Natural killer cells are large granular lymphocytes, they kill infected cells, they are an important source of interferon-gamma, NK cells recognise missing self, stressed cells, certain viral proteins. After it recognises these it either kills or produces interferon
NK cells kill cells with granzymes which they store which enter target cell via perforin pores. granzymes activate caspases which lead to apoptosis.
perforin pores are pores which are made my perforins (which are stored in NK cells) in the cell (pore is not usually there)
where is MHC class 1 found
all cells have MHC class 1, missing self is lack of MHC class 1, this can happen in cancerous tumours or in certain infections
what are proffesional antigen presenting cells
dendritic cells, since they are the only cells that can present to nieve T cells
immature DCs have high antigen uptake and are very phagocytic, when they take up the antigen they become mature
when they are mature they look different and have low antigen uptake and become more antigen presenting
immature DCs have chemokine receptors (CCRs), immature DCs have CCR1,2,5 and 6 and 7
mature DCs only have CCR7
follicular dendritic cells are very different, they are specialised and located in germinal centres of secondary lymphoid tissues, they do not undergo same phagocytosis/ antigen presenting process as other DCs
