Distribution of electrophoretic mobilities of mouse thymocyte subpopulations in the presence of tumour cells.

Analysis of the electrophoretic mobility of mouse thymus cells has showed two main populations, with mean mobility values of 0-77 +/- 0-023 mum s-1 V-1cm and 0-99 +/- 0-015 mum s-1P1cm; these absolute values varied slightly from one strain to another. Implantation of tumour cells caused the relative proportions of these two populations to change dramatically within 48 hours, when an increase in the fast-moving 'immunocompetent' thymocytes was observed. The ratio of slow to fast cells changed from 9:1 in the normal BALB/c animal to 2:1 in the presence of the tumour cells and this 2:1 ratio persisted throughout the remainder of the animal's life. However, inoculation of histocompatible spleen cells from a normal individual evoked only a brief response in the host's thymus. This change in ratio of slow to fast cells in thethymus was interpreted as an increased production of immunocompetent cells in response to the presence of the tumour cells.