Degranulation of chicken heterophil leucocytes during phagocytosis, studied by phase contrast and interference microscopy.

The dynamic aspects of degranulation of chicken heterophil leucocytes during phagocytosis have been studied by phase contrast and interference microscopy. Both standard (8 fps) and high-speed (400 fps) cine-photomicrographic recordings of this process under phase contrast are presented. Lysis of individual granules is usually completed in less than 60 milliseconds. During lysis of each granule a rounded phase dense body is ejected into the phagocytic vacuole. Measurements made by interference microscopy show that there is usually a substantial fall from a protein concentration of c. 100 per cent. w/v for intact granules to a concentration of 16 per cent. w/v for the vacuole resulting from their lysis; this can only be explained by a rapid intake of water into the granule matrix following membrane fusion. The intake of water that accompanies granule lysis causes swelling of the granule matrix, and is thought to explain the mechanism of ejection of the phase dense body. Granule lysis is not dependent on the intake of water, since occasional vacuoles have been observed which showed no fall in protein concentration relative to the intact granules. The membrane around the intact granule effectively excludes the entry of water into the concentrated hygroscopic granule matrix, but once membrane fusion occurs this barrier to the entry of water is usually lost.