A Comparative Study of Phagocytosis and Digestion of Pneumococci by Macrophages and Polymorphonuclear Leucocytes in Normal and Immune Dogs

Abstract

Summary A comparative study was made of the phagocytosis and digestion of pneumococci by macrophages and polymorphonuclear leucocytes in normal and immune dogs. Cellular exudates of the two types of cell were produced in dogs by the intrapleural injection of gum arabic on the one hand, and aleuronat on the other. Observations were carried on both in vivo and in vitro employing a highly virulent Pneumococcus type I. It was found that while the macrophages showed a somewhat greater phagocytic activity than the polymorphonuclears their ability to digest pneumococci was much more pronounced than that of the latter cells. This difference was most marked in the presence of opsonic fluids of relatively low concentration. The use of suspensions of macrophages which had been concentrated by differential sedimentation brought out the superior antipneumococcal activity of these cells most clearly. Macrophages secured from the pleural exudates of dogs highly immune to pneumococcus as well as from the lungs of dogs recovering from experimental pneumonia were found to be just as dependent on opsonins for the phagocytic activity as were cells of normal animals.