REPORTS on phagocytosis of viruses and the organisms of the psittacosislymphogranuloma-trachoma group are sporadic (Sabin, 1935 ; Florman and Enders, 1942; Merling, 1945).Observations of the fate of intracellular virus are comparatively more recent (Barski and Robbe-Fossat, 1957; Benedict and McFarland, 1958). The interaction of viruses with leucocytes has been shown to lead to (1) alteration in certain of the metabolic and phagocytic activities of the leucocytes (Merchant and Morgan, 1950; Fisher and Ginsberg, 1956), (2) agglutination of the leucocytes (Nungester, Gordon and Collins, 1950; Boand, Kempf and Hanson, 1957; Nishmi and Fkrnkopf, 1958; Shechmeister and Parikh, 1961 ; Parikh and Shechmeister, 1967), and (3) phagocytosis and multiplication of the virus (Dunne, Luedke and Hokanson, 1958; Parikh, Shechmeister and Yen, 1963). Smorodmtsev (1960), in reviewing the role of leucocytes in viral infections, stated that phagocytosis is not an important natural defence mechanism, except with the psittacosis-lymphogranuloma-trachoma group. However, the role of blood leucocytes, macrophages and other cells of the reticulo-endothelial system in the viral diseases has not been studied systematically. This is particularly true for phagocytosis of viruses by leucocytes in vitro and in vivo, which may explain in a relatively simple manner certain aspects of virus-host cell interaction.This report presents evidence for phagocytosis and multiplication of meningopneumonitis organisms (MP) in leucocytes (WBC) and stresses the importance of the MP:WBC ratio in determining the extent of intraleucocytic replication.
MATERIALS AND hETHOD.5 Preparation of MP organismsProduction and concentration of MP suspensions. The Cal 10 strain of MP organisms, originally isolated by Francis and Magill (1938) was kindly supplied by Dr J. M. Moulder of the University of Chicago. The organisms were grown in the yolk sac of embryonated hen eggs by inoculating 0.5 ml. of a 1 in 100 dilution of the agent in each 5-to 6-day-old chick embryo and harvesting the yolk sac after 5 days' incubation at 37°C. No antibiotics were used, and freedom from bacterial contamination was determined by culturing in thioglycollate broth. Preliminary estimates of the concentration of MP were made by examination of smears of yolksac membrane stained with Macchiavello's stain. Infected yolk sac was ground in a homogeniser, or by mortar and pestle, in nutrient broth, the ratio of yolk-sac material to broth being 1 in 10, and then centrifuged at 4°C at 3020g for 30 min. Yolk-sac material and debris were discarded, and the supernatant was recentrifuged
