Differences in the rates and extents of fusion between lysosomes and phagocytic vesicles containing different...

The rates and extents of fusion between lysosomes and phagocytic vesicles containing different kinds of particles were investigated kinetically in guinea pig polymorphonuclear leukocytes (PMNs). Particles were prepared by emulsifying paraffin oil with bovine serum albumin (POE-BSA), with hemoglobin (POE-Hb), and with ovalbumin (POE-OA). PMNs phagocytosed these particle in the order, POE-BSA greater than POE-Hb greater than POE-OA. As for fusion with lysosomes, the recoveries of lysosomal enzymes in the phagolysosome fraction during phagocytosis did not vary greatly, but the ratios of lysosomal enzymes to paraffin oil in the phagolysosome fractions, designated as "the fusion index," showed considerable differences, varying in reverse order to that of phagocytosis. Further studies were carried out on fusion between lysosomes and phagocytic vesicles as distinct from phagocytosis. PMNs were allowed to phagocytize particles at 37 degrees C for 5 min, then were washed free from non-ingested particles and reincubated without phagocytizable particles. The fusion index showed a slow but continuous increase in cells with POE-BSA, and a rapid but temporary increase in those with POE-Hb and POE-OA at 37 degrees C. These results suggest that different particles caused differences in the rate and extent not ony of phagocytosis but also of fusion with lysosomes.