CPN1 and leukemia: The magnitude of immune response evoked by L 1210 cells preincubated with 250 u/ml of VCN or 35 μg/ml of CPN for 60 minutes was of relatively low level when compared with the immunity induced by leukaemia cells preincubated with 50 u/ml of VCN or 15 μg/ml of CPN for 30 or 60 minutes.