ABSTRACT
Current hypotheses suggest that autoimmune hepatitis (AIH) is triggered by an environmental
factor in a genetically susceptible host. Multiple genes may interact to produce a
``permissive gene pool'' that determines both disease risk and phenotype. Studies
of type 1 AIH have focused on the major histocompatibility complex (MHC), mapping
susceptibility to the DRB1 region. Three different molecular models have been proposed based on histidine at
DRβ13, lysine at DRβ71, and valine at DRβ86. Although the lysine-71 model has been
adapted to explain data from several other studies, the DRβ13 and DRβ86 models are
exclusive to their founder populations. It is possible that all three models apply
and that the different associations reflect the ``molecular footprint'' of the common
environmental triggers in the different study populations. Studies outside the MHC
have identified the CTLA4 A+49G, G allele as a possible second risk allele. There are many neutral polymorphisms in
the genome, and further studies are currently needed to identify other disease alleles
in type 1 AIH.
KEYWORDS
Genetic susceptibility - MHC - CTLA4 - permissive gene pool - molecular footprint