Experimental Mouse Plasmacytoma: Presence of two Populations of Plasma Cells

In mouse plasmacytoma experimentally induced with mineral oil, the presence of two plasma cells populations has been observed with the electron microscope. The most evident difference between them is represented by a different electron density, as to permit to classify them into « dark » and « light » cells. The higher electron density is ascribed to a higher cytoplasmatic concentration of ribosomial granules and mainly to a particular abundance of proteic material in the hyaloplasmic matrix. The possibility is discussed either that both the plasma cells populations really represent two different cellular kinds or, on the contrary, that they belong to the same cellular stem in a different functional behaviour or in a different maturation phase.