Flashcards in Immunology Deck (160)
list some of the consequences of immune system malfunction
what are the cells of the innate immune system?
antigen presenting cells (dendritic cells, macrophages)
what are the cells of the adaptive immune system?
what are the features of the innate immune system?
broad specificity, resistance not improved by repeat infection.
rapid response (hrs).
what are the features of the adaptive immune system?
SPECIFICITY + MEMORY.
highly specific. resistance improved by repeat infection.
slower response (days-weeks)
describe the main differences between the innate and adaptive immune system
innate = broad specificity, adaptive is highly specific. adaptive resistance is improved by repeat infection. adaptive takes days-weeks, innate is rapid.
what are the external barriers to infection?
keratinized skin; secretions; mucous; low pH; commensals
what soluble factors are involved in innate immunity?
what soluble factors are involved in adaptive immunity?
what is the purpose of pattern-recognition receptors?
to discriminate self from non-self by recognising unchanging patterns of microbes
how do pattern recognition receptors work?
recognise conserved polysaccharide molecular patterns on microbes - patterns that are constant across a group of bacteria for eg.
what do pattern recognition receptors activate?
innate immune system.
damage recognition receptors on dendritic cells.
what are cell-associated PRRs?
receptors present on cell membrane/in cytosol. recognise broad range of molecular patterns.
name some membrane-bound PRRs
TLRs are main family.
mannose receptor on macrophages - fungi
dectin-1 - phagocytes, beta glycans in fungal walls.
scavenger receptors on macrophages.
what does TLR4 bind to?
lipopolysaccharide in bacterial walls.
pneumolysin, viral proteins.
what do TLRs do, once activated?
induce signal transduction and cellular events, leading to induction of pro-inflammatory cytokines.
what causes a hyperacute rejection of a transplanted organ?
when there are preformed cytotoxic antibodies against the MHC class I antigens in graft (e.g. previous pregnancy that generated antibodies, or blood-group incompatibility)
describe acute rejection of a transplant
occurs weeks-months after. T lymphocyte mediated reaction against donor HLA, or can be antibody mediated.
febrile, tenderness, declining renal function.
describe chronic rejection (chronic allograft injury)
after 6m of transplant - progressive decline of renal function. proteinuria. hypertension.
immune and non-immune mechanisms.
how can we prevent transplant rejection?
why are immunosuppressants given to transplant patients?
preventing rejection. must be taken indefinitely (non-compliance).
what gene codes for human leucocyte antigens (HLAs)?
MHC (major histocompatibility complex) on chromosome 6
describe the process of hyperacute rejection
preformed cytotoxic antibody reacts with MHC class I antigens. activation of complement. influx of PMN leukocytes. platelet aggregation. obstruction of blood vessels - ischaemia. microvasculature plugged with leukocytes/platelets - infarction.
how is acute rejection treated?
IV methylprednisolone, anti-CD3 antibody, or increase other immunosuppressive drugs
what are the two phases of transplant rejection?
afferent phase - initiation or sensitising component.
efferent phase - effector component.
what occurs in the afferent phase of transplant rejection?
donor MHC molecules in the graft are recognised by CD4+ T cells - allorecognition
what occurs in the efferent phase of graft rejection?
CD4+ T cells recruit macrophages/CD8 T cells/NK cells/B lymphocytes to graft - tissue damage.
describe the structure of a typical antibody molecule
two Fab regions attached to an Fc region by a hinge.
Fab = variable sequence
Fc = constant.
2 light chains and 2 heavy chains
what do the Fab regions of antibodies bind?
antigens - specific