Plasma cells (spleen, mouse)

Electron microscopy. The mature plasma cell shows an eccentric nucleus with a characteristic chunky distribution of heterochromatin along the inner nuclear membrane ('spoke-wheel' effect in light microscopy). Juxta-nuclearly an elaborate Golgi area (2) with secretion vacuoles is localized (cytocentrum/centrosome). The cytoplasm is packed with long dilated profiles of rough endoplasmic reticulum (RER) filled with electron-grey material (1) confirming the production of antibodies. The amount of RER and the degree of dilation are indicative for the activity of the plasma cell. In light microscopy this results in the deep basophilia of the cytoplasm and the light-stained centrosome (so-called nuclear 'hof').