Mononuclear Leucocytes in Blood of Guinea Pigs Experimentally Infected with Pneumococcus

Abstract

In view of the importance attached by many observers to the rôle of mononuclear cells in recovery from infection and especially the concepts advanced by Robertson and his coworkers 1 2 3 4 in pneumococcal infection in dogs, the changes in the mononuclear cells in the circulating blood have been studied in guinea pigs that died and that recovered spontaneously from experimental pneumococcal infection. The animals were infected by intraäbdominal injection of 0.25 cc of an 18-hour dextrose-serum-broth culture of Type I pneumococcus. Of 100 animals so infected 47 survived the infection. In this study of the mononuclear leucocytes 14 animals that died from 60 hours to 30 days after infection (Group C), 18 that recovered at 5 to 9 days after infection (Group D), and 14 that recovered on the fourth day (Group E) are considered. Recovery was assumed to have occurred on the day a negative culture was obtained from the peritoneal exudate.

At 6 hours after infection there was a decrease in the number of circulating mononuclears and this decrease was usually still evident or may have been more marked at 24 hours. The changes were observed in all groups regardless of whether death or survival follows (Table I).

In Group C, in those animals that died before the third but after the second day, the mononuclears continued to decrease after 24 hours; this change was concomitant with a decrease of total cells and of neutrophils. 5 Those animals that died on the fourth day showed a further decrease on the second day; however, on the third day these latter animals (which died within the next 24 hours) showed a distinct increase in the mononuclear cells.