Trapping and destruction of blood-borne syngeneic leukaemia cells in lung, liver and spleen of normal and leukaemic rats.

Leukaemic cells from rats with a lymphoid (HRL) or myeloid (SAL) leukaemia were labelled with 125IUDR and injected i.v. into either normal or leukaemic syngeneic recipients. The fate of the injected cells was studied in terms of the radioactivity in various tissues at various times up to 24 h later. In normal animals the leukaemia cells were destroyed rapidly in the reticulo-endothelial (RE) system; immediately after injection most recoverable activity was in the lung, with smaller amounts in the blood, spleen and liver but by 24 h only 20-30% of the injected activity could be recovered. In leukaemic recipients with high numbers of blasts in the blood the amount of activity recoverable from the lungs and bone-marrow was markedly reduced, while that in the blood was doubled. Nonetheless, the overall rate at which radioactivity was eliminated was not significantly different from that found in normal rats, in spite of the fact that the RE system was extensively infiltrated by leukaemia cells.