1. overview of immunology Flashcards
what is the main role of the immune system?
protect from infection
what is an antigen?
anything the immune system responds to
usually a protein
not necessarily bad
what is an antigen receptor?
recognises antigen
fundamental basis of immunity
basis of division into innate and adaptive immunity
what is effector mechanism?
an action to respond to the antigen
what is the difference between innate and adaptive immune systems?
innate = germline encoded, pattern-recognition receptors (PRRs) adaptive = antigen-specific T and B cell receptors
leukocytes from myeloid lineage
neutrophils eosinophils monocytes/macrophaes dendritic cells basophils/mast cells
leukocytes from lymphoid lineage
b cells - adaptive
t cells - adaptive
nk cells - innate
types of intracellular signalling
endocrine (hormonal - long distance)
paracrine (short distance)
autocrine (self signalling)
juxtacrine (membrane bound signal molecule)
what are cytokines?
small proteins released by cells which have an effect on another cell
what do cytokines do?
important for communication between cells of the immune system and between immune system cells and other cells/tissues
what are chemokines?
have different structure, receptors and nomenclature to cytokines
important for attracting cells to site of inflammation
what do chemokines do?
main role = temporal and spatial organisation of cells/tissues
chemo-attractants (induce chemotaxis)
what are antigen receptors?
receptors that cells use specifically to recognise antigen
key in immunology
basis of separating innate and adaptive immunity
innate antigen receptors key factors
do not recognise antigen specifically
pattens recognition receptors (PRRs) recognise pathogen associated molecular patterns (PAMPs)
genome encoded
not clonally distributed
what is mannose binding lectin?
opsonin used in lectin pathway
binds to mannose and fructose residues on user face on many pathogens
residues must be present with correct spacing
targets cell for destruction
classical features of innate immune receptors
work quickly
adaptive immunity takes more time to be activated
unable to ‘learn’
gremlin encoded, cannot change, no memory
key features of adaptive antigen receptors
recognise antigen specifically t cell receptor, b cell receptor produced by random somatic recombination events between gene segments huge receptor diversity clonally distributed permit specificity and memory
b cell receptors
(|antibodies)
may be surface bound or secreted
recognises intact antigen
t cell receptors
very similar to b cell receptor
only present on cell surface (CD8 and CD4 t cells)
recognises processed antigen in form of linear peptides
how are adaptive immune receptors produced?
somatic recombination events - between v, (d) and j segments
huge receptor diversity despite small number of genes
useful receptors selected after birth on exposure to pathogens
t and b cell memory
after primary cell infection, most clonally-expanded t and b cell lymphocytes die off
few remain as long-lived memory cells
how does clonal selection work?
- large population of cells with different receptors
- introduction of foreign antigen
- receptors which bind to antigen are positively selected
- cells with receptor for antigen are replicated rapidly
examples of effector mechanisms
barriers (skin, acid pH) cytokines complement phagocytosis cytotoxicity (CD8 T cell, NK cell) antibody-dependent cellular cytotoxicity mast cell and eosinophil granulation
how to CD8 t cells kill virally infected cells?
virus infects cell
viral proteins are synthesised in cytosol
peptide fragments of viral proteins bound by MHC class I in ER
bound peptides are transported by MHC class I to cell surface
CD8 T cells recognise peptide+MHC class I complex - kill cell
