Polyclonal increase of HTLV-I provirus-carrying lymphocytes in HTLV-I-carrier rabbits transplanted with Shope carcinoma cells.

Fifteen HTLV-I carrier rabbits of two inbred strains and their F1 hybrid were inoculated with Shope carcinoma cells. The peripheral blood leukocyte counts in all these rabbits increased to 2-4 times the preinoculation level with a concomitant increase in abnormal lymphocytes. Southern blotting analyses of peripheral blood leukocytes revealed the polyclonal integration of HTLV-I proviral genome in all these animals. However, lymphocytic infiltration without any apparent leukemic infiltration was observed in major organs of these animals; a similar but slight lymphocytic infiltration was also observed in non-carrier control animals inoculated with Shope carcinoma cells. These results are interpreted as indicating that the growth of squamous cell carcinoma in HTLV-I carrier rabbits induced the polyclonal expansion of provirus-carrying cells, which may correspond to the intermediate state between healthy carrier and smouldering ATL.