Since MHC I is an endogenous antigen-presenting molecule that mainly recognizes and presents viruses to CD8+ T for paralysis, this implies that the ability of the SN Tibetan pig liver to defend against viral infection is enhanced mainly by up-regulating the expression of MHC I (SNT/LZT, 1.42-fold; SNT/JZT, 1.39-fold). Here, CD8A is linked to viral infectious disease.