THE IMMUNE-REACTION TO HETEROLOGOUS SERUM CAUSES OSTEONECROSIS IN RABBITS

Osteonecrosis (ON) was produced experimentally in rabbits by intraveno us injection of horse serum. Eighty adult rabbits were used: 16 were i njected twice with isotonic saline (Group A), 24 were injected once wi th saline and once with horse serum (Group B), and 40 were injected tw ice with horse serum (Group C). Both femurs of each rabbit were obtain ed from 2 h to 7 weeks after the final injection an were subjected to histological examination. No pathological changes were seen in Groups A and B. In Group C, 5 of 15 rabbits (33%) showed ON (necrosis of trab ecula and bone marrow) in the femoral metaphysis. In Group C, the earl y major pathological findings in bone marrow are extravasation of eryt hrocytes in sinusoidal spaces and microthrombi in small arteries and a rterioles near the lesion of extravasation, Immune complexes were demo nstrated in the kidney within 24 h of the final injection of horse ser um. The present study suggests that immunological reaction associated with serum sickness may play an important role in inducible ON and thi s model will contribute toward clarifying the pathogenesis of ON.