MHC and Transplant Flashcards
what’s the difference between class 1 HLA and class 2 HLA in structure
1 - beta pleated sheets at bottom and 2 a helics which the antigen sits in between - forms with beta 2 microglobin
2 - more selectively expressed - heterodimers - alpha and beta chain - is in all cells that are nucleated
what is the gene sequence for the human MHC
HLA gene on chromosome 6 (p)
how many types of class 1 and 2 HLA genes are there
class 1 - 3 types - A, B and C
class 2 - DR type - DR-A forms alpha and DR-B forms beta
what about HLA molecules make them variable
highly polymorphic, space between 2 alpha helics
what’s the difference in target of class 1 vs class 2 MHC
1 - peptides from intracellular organisms such as fungi and virus
2 - protein peptides that have been endocytosd within cells and presented on the surface - against pathogens
what gene is associated with ankylosing spondylitis
if you have HLA allele B27
what gene is associated with good pastures syndrome
HLA DR 2
what is the difference between HLA and MHC
MHC is in most vertebrates but HLA is the human version of MHC
what are the benefits and disadvantages of MHC genes becoming HLA molecules
aid against pathogens
more susceptible to different autoimmune diseases and transplant rejection
describe how MHC restriction works
a T cell will only react when presented to a recognisable MHC molecule with the antigen
therefore an immune response will only happen to a recognisable MHC x antigen
what is the difference between autologous and allogenic cells
auto - self cells not recognised therefore no immune response
allogenic - non-self and produces immune response
how does rejection occur in transplantation and what are the three effector pathways
CD4 T helper cells recognise from APC as different - effector pathways
interact with B cells in lymph to make antibodies
activate cytotoxic CD8 T cells
delayed relay reaction CD cells causing influx of macrophages (delayed hypersensitivity reaction DTH)
what type of assay is used for HLA typing to identify antibodies against a transplant
luminex screening
what are the there types of transplantation rejection
acute antibody mediated rejection - hyper acute reaction, activation of complement - MAC, recruitment of cytokines/macrophages
acute cellular rejection - T cell dependant typically 7-10 days after transplant
chronic antibody mediated rejection - no treatment and requires monitoring
