The sand lizard is a species of conservation concern in Sweden. It's populations are small and fragmented with low, but variable, genetic diversity. A genetic rescue experiment has established an admixed population via cross-breeding of several sand lizard populations that shows higher genetic diversity, reduced levels of deleterious mutations and no signs of inbreeding. I study to what extent genome-wide diversity determines functionally important genetic diversity at the immune genes of the major histocompatibility complex (MHC) and how that in turn affects parasite infection diversity. I further aim to understand the evolutionary dynamics of the MHC in the sand lizard and among squamates, making use of available high-quality reference genomes and assembling additional sand lizard genomes.