Genetic markers for disease resistance are difficult to determine due to the complex  relationship between environment, host, and pathogen. One theory is that disease susceptible animals have genetic defects in proteins involved in resistance – either in the amino acid sequence, or promoter and regulatory sections. One part of the research in this area identified SNPs on collagenous lectins, and in diseased pigs SNPs for low production/expression were found. A larger scope project looked at over 20,000 genes in the liver, and created a gene expression ratio between the highest and lowest expression groups. Gene variants were identified, and differences between healthy and diseased pigs examined. Identifying the genes responsible for the immune response would allow selection of naturally disease resistant pigs for future breeding.