Abstract
In studying smears of bone marrow aspirates stained with May-Giemsa, we occasionally encounter the presence of some cells within another cell. It cannot be exactly decided whether this phenomenon is emperipolesis or phagocytosis by only light microscopy. Electron microscopy is an important method to differentiate emperipolesis from phagocytosis. We can easily observe whether engulfed cells are intact or not, and whether engulfing cells are developed lysosomes, vacuoles etc. or not. Tests of phagocytic activity of the engulfing cells are also important. The staining of the plasma membrane confirms that some cells do not look as if they are contained inside another cell because of the invagination of the plasma membrane of another cell (pseudo-inclusion).
Phase contrast microscopy is also a good technique to differentiate both phenomena. Mitochondria etc. of an engulfing cell and of the engulfed cells are seen to move, and the engulfed cells are also seen to be actively moving inside the engulfing cell. This is evidence that the engulfed cells are actually living within the live engulfing cell.
We compared emperipolesis or phagocytosis according to these above methods.
