Abstract: The present disclosure relates in general to the generation of transgenic rats having incorporated into their genome a selected transgene. However, in particular aspects, the present invention concerns the introduction of an HLA-B27 or DR4 gene into the rat genome, or that of other non-human mammals other than mice, to produce transgenic lines having the propensity to spontaneously develop an inflammatory disease trait including inflammatory lesions of the peripheral or axial joints, gastrointestinal tract, genital tract, nails, skin, eye, lungs or heart. This is preferably achieved through the co-introduction of a human HLA-B27 gene together with a human beta-2 microglobulin gene into fertilized eggs from superovulated female rats, which eggs are then brought to term in a pseudopregnant female. The resulting offspring are employed to generate transgenic lines from which lines exhibiting the desired traits are selected and maintained.