DNA present in multilayer rosette formed by lymphocytes stimulated with phytohaemagglutinin

Abstract

ROGERS et al.¹ have reported that human lymphocytes of peripheral blood cultured in the presence of phytohaemagglutinin (PHA) undergo blast formation and synthesise DNA. This newly synthesised DNA which is excreted into the medium is reported to have a high molecular weight. The release of DNA by the cells is selective, as experiments with ¹⁴C-uridine indicated that RNA was not lost into the culture medium. The excretion of DNA by lymphocytes has also been noted by Olsen and Harris². Sarma and Rutman³ also found that PHA-stimulated lymphocytes incorporated labelled thymidine into small fragments that were then converted to high molecular weight material. Subsequently, the labelled thymidine reappeared in light fragments that were then released into the medium in an acid-precipitable form. It has also been reported that the human lymphocytes of peripheral blood are able to bind to sheep red blood cells (SRBC) in a rosette-forming cell⁴ when incubated together in stringent temperature conditions. In view of these findings the release of DNA synthesised by lymphocytes has been studied in connection with rosette formation.