Adult T Cell Leukemia‐like Disease Experimentally Induced in Rabbits

An HTLV‐I‐transformed T cell line, obtained from the peripheral blood of a virus‐infected (B/J × Chbb:HM) F1 rabbit, was able to kill syngeneic newborn rabbits within 7 days, when inoculated intraperitoneally at a dose of 1 × 10(8) cells. Inoculation of 1 × 10(7) cells killed or rendered moribund 50% of inoculated animals, while surviving animals exhibited cell‐mediated cytotoxic activities against the transformed cells. The peripheral blood leukocyte counts increased in all surviving animals, in association with appearance of abnormal lymphocytes with convoluted or lobulated nuclei. Pathological examination of animals that died one week post‐inoculation revealed no tumors in the abdominal cavity, but accumulation of ascites containing abnormal lymphocytes. Histological examination showed leukemic infiltration in the liver, lungs, spleen and mesenteric lymph nodes. The same cell line was also able to kill syngeneic adult rabbits in 8–10 days when inoculated intravenously, but not intraperitoneally, at a dose of 1 × 10(8) cells. Leukemic infiltration was observed in the major organs of these animals. Adult animals which were already virus carriers were resistant to this lethal inoculation. This rabbit ATL‐like disease may prove to be useful as an experimental model for acute adult T cell leukemia.