Cross-reactivity between Bacillus Calmette-Guérin and Rous Virus-induced sarcoma detected in rats by tube leukocyte adherence inhibition assay.

Specific immunity to Rous virus-induced sarcoma (RSL) was investigated by the tube leukocyte adherence inhibition (LAI) assay in rats immunized with Bacillus Calmette-Guérin (BCG). Peritoneal cells from Lewis rats immunized s.c. with BCG gave positive reactions in the tube LAI assay with the antigen prepared from RSL in Lewis rats. Lymph node cells from Lewis rats immunized with BCG had no cytotoxic effect on RSL cells in vitro, whereas peritoneal cells from the same rats were strongly cytotoxic for RSL cells. Growth of RSL tumors in vivo was not inhibited in BCG-treated rats as compared to that in untreated rats. The results show that LAI reactivity correlates with cytotoxicity of peritoneal cells and does not correlate with the cytotoxicity of lymph node cells and that positive LAI reactions with tumor antigen need not be reflected in the suppression of growth of the tumor in vivo.