The present invention relates to the engineering of animal cells, preferably mammalian, more preferably rat, that are deficient due to the disruption of gene(s) or gene product(s) resulting in cytokine-cytokine mediated autoimmune and inflammatory disease. In another aspect, the invention relates to genetically modified rats, as well as the descendants and ancestors of such animals, which are animal models of human autoimmune and inflammatory disease and methods of their use. Specifically, the invention pertains to a genetically altered rat, or a rat cell in culture, that is defective in at least one of two alleles of a cytokine gene such as the Faslg gene, the Fas gene, etc. In one embodiment, the cytokine gene is the Faslg gene. In another embodiment, the cytokine gene is one of several known cytokine genes, such as Fas, IFNγ, TNF-α, IL-2, IL-10, and IL-12. The inactivation of at least one of these cytokine alleles results in an animal with a higher susceptibility to cytokine-cytokine mediated autoimmune and inflammatory disease induction. In one embodiment, the genetically altered animal is a rat of this type and is able to serve as a useful model for cytokine-cytokine mediated autoimmune and inflammatory disease and as a test animal for autoimmune and other studies.Linvention porte sur le génie de cellules animales, de préférence mammaliennes, et de préférence de rats, qui sont déficientes en raison de la disruption dun ou plusieurs gènes ou produits géniques et provoquent par conséquent une maladie auto-immune et inflammatoire médiée par la cytokine-cytokine. Selon un autre aspect, linvention se rapporte à des rats génétiquement modifiés, ainsi quaux descendants et aux ancêtres desdits animaux, qui constituent des modèles animaux dune maladie auto-immune et inflammatoire humaine, et à des procédés dutilisation de ces derniers. Linvention concerne, en particulier, un rat, ou une cellule de rat en culture, génétiquement modifié qui est déficient en un allè
