[Electron microscopic study of Ag-protein localization in the nucleoli of human lymphocytes]

The present study was undertaken to provide more information on the ultrastructural localization of a silver reaction in normal resting and stimulated lymphocytes as well as leukaemic resting lymphocytes. The results obtained indicated that in the ring-shaped nucleoli of normal mature lymphocytes silver stained proteins (SSPs) were present mostly within single fibrillar centers. In the nucleoli of lymphocyte cultures, being in the presence of phytohemagglutinin (PHA) for 6--72 hours, SSPs formed finger or loop-like protrusions from fibrillar centers towards the adjacent areas of the nucleoli. In the ring-shaped nucleoli of mature leukaemic lymphocytes SSPs are present not only within fibrillar centers, but also in protrusions diverging from fibrillar centers into the surrounding peripheral nucleolar ring. In this respect the nucleoli of leukaemic mature lymphocytes were similar to normal lymphocytes shortly after mitogen stimulation.