Cell proliferation during immunological perturbation in three transplanted tumours.

The cell population kinetics of 3 transplantable tumours has been studied under circumstances in which the tumour growth rate was modified by a disturbance of the immunological status of the host. In 2 cases a complete arrest of growth was achieved but in spite of this there was a barely significant change in the median intermitotic time of proliferating cells. The data indicate that growth retardation was associated with a reduction in the proportion of actively proliferating cells and the rate of cell production, with or without an increase in the absolute rate of cell loss.