Uptake and release of DNA by lymphoid tissue and cells.

Newly synthesized DNA has been shown to be released by immunized rabbit spleen tissue cultured . This DNA was mainly doublestranded, showed a large spread in buoyant density, and was in the molecular weight range 50,000–500,000. Rabbit spleen tissue and human peripheral blood lymphocytes in active DNA synthesis, also took up bacterial DNA into their nuclei. After short periods of culture this DNA had a buoyant density of the bacterial DNA employed. Upon prolonged incubation, the DNA was of mammalian density. Evidence was obtained, in the case of the blood lymphocytes, for the appearance in the cells of a DNA of intermediate buoyant density. The possible relevance of the loss and reutilization of DNA to lymphoid cell function is discussed.