Objective: We have recently reported that arthropathy develops in high incidence among transgenic mice carrying the pX region of human T cell leukemia virus type I (HTLV-I). In the present study, the histopathologic features of the joints in these mice were examined in order to compare the animal disease with rheumatoid arthritis (RA) in humans.
Methods: Paraffin sections of limbs (right and left fingers, wrists, elbows, shoulders, toes, knees, and ankles) were stained with hematoxylin and eosin, periodic acid-Schiff, azan-Mallory, or phosphotungstic acid hematoxylin, and examined by light microscopy.
Results: Abnormalities of the limbs began to occur as early as 3 weeks of age, and the incidence gradually increased until the mice were 12 months old. The incidence of arthropathy was 22% (48 of 217) at 3 months of age and 28% (18 of 64) at 6 months. The severity of the histopathologic changes in the joints of the transgenic mice ranged from grade I to grade IV.
Conclusion: The major histopathologic features in the joints of HTLV-I transgenic mice are similar to those in humans with RA. Thus, these mice may represent a useful model for the study of the disease in humans.