Transport of DNA from lymphocytes to fibroblasts in culture.

The exchange of radioactivity between lymphocytes, labelled with (3H) thymidine after stimulation with Concanavalin A, and recipient V79 fibroblasts in culture was studied. The radioactive material involved in this exchange was macromolecular deoxyribonucleic acid as well as its breakdown products. This deoxyribonucleic acid from lymphocytes localised in the nuclei of the host cells soon after contact between donor and recipients. This occurred even when the V79 fibroblasts were confluent at high cell density, and thus in a steady, non-growing state with respect to cell numbers. The fate of the radioactive donor lymphocyte deoxyribonucleic acid, substituted with bromodeoxyuridine, was followed in the recipient cells by analysing its buoyant density in caesium chloride gradients. This deoxyribonucleic acid was found to become associated with the nuclear deoxyribonucleic acid of the host cells, involving both retention of relatively intact donor deoxyribonucleic acid as well as its breakdown and re-utilisation for host cell deoxyribonucleic acid synthesis. Non-growing recipient cells were found to retain the donor deoxyribonucleic acid in relatively intact form for much longer periods than when the same cells were in logarithmic growth phase.