Morphometrical method for estimating mean cell volume of phagocytosing cells

A method is described for the estimation of mean cell volume of phagocytosi ng cells. The cells are coembedded with yeast particles of known size. By c ombination of data obtained from morphometrical analysis of sections in bot h the light and transmission electron microscopes, an estimate of the ratio between cell volume and yeast particle volume is obtained. The method make s use of the dissector but does not require measurements on serial sections or knowledge of section thickness. Evaluation of the method was done by st udying the effect of phagocytosis of latex beads on macrophage cell volume and surface area. It was found that the surface area of phagocytosing macro phages remained constant although the cell volume increased by 27%. Further more, in phagocytosing macrophages, the amount of membrane enclosing intrac ellular vacuoles decreased by 28%, but this loss of membrane was balanced b y the appearance of membrane enclosing the phagocytosed latex beads. The me thod described here may prove useful for morphometrical studies on phagocyt osing leukocytes, as well as on intracellular parasites located within thes e cells.