An ultrastructural study of renal plasma cells in aged mice *
In mice older than 180 days of age, solitary lymphatic tissues occurred at corticomcdullary junction in the kidney, and were characterized by the presence of a numher of plasma cells. Plasma cells gathered in groups in the connective tissues of arcuate vessels, and a few of ihem were also scattered either singly or in small groups in narrow conncctivc tissue in the renal cortex. The lymphatic tissues contained. not only mature plasma cells, but also piasmabiasts with a large nucleus, and mitotic figures. Dying plasma cells with heterochromatin condensation along the nuclear envelope could also be recognized, and macrophages often contained large hetcrophagosomes derived from apoptotic plasma cells. The plasma cell nucleus contained not only nucleoli, but also nuclear bodies, which measured 0.1~～1.0μm in diameter. The frequency of nuclear bodies in plasma cell sections was very high, with 42 2% of all renal plasma cells containing one or more nuclcar bodies. Nuclear bodies were seldom observed in piasmabiasts but dying cells contained a few. On the basis of ultrastructural features, the nuclcar bodies were classified into four types ; fibrillary, fibrillogranular, concentric nuclear bodies and fibrillary nuclear bodis containing vesicles. Of these, 77.1% were of the fibrillary type and 18.6% were of the fihrillogranuiar type. (Accepted on September 21, 1999) Kawasaki Igakkaishi 25 ( 4 ) : 269-278, 1999
