Histological Observations on Resistance to Transplantable Leukemia in Immunized Mice

Abstract

Recently it has been demonstrated that immunization to transplantable lymphatic leukemia in mice can be actively induced by suitable injection of dilute doses of leukemic cells, by injection of normal lymphoid cells, and of embryo skin. Naturally susceptible mice so treated are resistant to injections of normally lethal doses of leukemic cells at subsequent inoculations. This paper records the results of preliminary observations on the fate of malignant lymphoid cells inoculated into immunized mice. A group of 19 mice of strain C58, immunized to line I transplantable lymphatic leukemia by dilute doses of line I cells as already described, were killed at intervals following inoculation of a massive dose; 1 at 13 1/4 hours, 1 at 1 day, 3 at 2 days, 7 at 3 days, 2 at 4 days, 1 at 5 days, 2 at 6 days, and 2 at 7 days. Unimmunized mice inoculated with this line die at 3 1/2 to 4 days following inoculation. The development of lesions of this line of leukemic cells in hosts of strain C58 as previously described forms a basis for comparison with the behavior of these leukemic cells in immunized hosts. Examination of the tissues from the immunized animals shows that at first the inoculated cells continue to proliferate. Lesions may appear in the same areas as in unimmunized mice but never become so large. The percent of cells in division is low (0.3%–1.0%) as compared with active lesions at all stages in unimmunized mice (4%–9%) inoculated with line I. Degeneration of the infiltrating cells usually takes place within the first 4 days. In only 2 animals out of the 14 killed after the second day were active lesions found without necrotic cells, but in these 2 animals necrotic lesions were also found, indicating that recovery was in progress.