To investigate possible factors in the failure of homotransplantation, the influence of in vivo irradiation of leukocytes on their subsequent ability to phagocytize bacteria was examined. Rabbits were exposed to a 848rad, whole-body dose of Co/sup 60/ gamma radiation, which was shown in previous experiments to be sublethal for the animals. At intervals, 1 to 50 days following irradiation, the rabbits were examined for changes in body wt, leukocyte count, and phagocytic activity. The latter function was evaluated by observing the in vitro ingestion of Staphylococcus aureus after incubation of bacteria and leukocytes, obtained from venous blood, for 1/2 hr at 37 deg C. Body wt began to fall on the 3rd day and fell maximally by the 15th day to 70% of the control level. Circulating leukocyte count fell from an initial value of 9400 per mm/sup 3/ to 1800 by the 3rd day; thereafter it rose gradually, to reach near normal values by the 50th day. On the lst day the percentage of neutrophils rose from 30 to 60% as the percentage of lymphocytes fell from 60 to 35%. For the next 15 days these more » changes were reversed as the proportion of lymphocytes began to climb sharply. Phagocytic activity declined precipitously up to the 3rd day, and thereafter more slowly, before beginning to rise again by the 25th day. On the 1st postirradiation day the percentage of granulocytes containing bacteria was 80%, compared with a control value of 100%. The lowest value (60%) was reached between days 8 and 15. By the 50th day it had risen to 90%. It is of interest in regard to transplantation immunity that the marked drop in phagocytic activity on the 3rd day coincides with the beginning of the rejection reaction in the recipient of a homograft. This fact should be observed when animals are preirradiated to prolong homograft survival. (BBB) « less

A. Puza

J. Simko

E. Kunstadt

CHANGES IN LEUKOCYTE PHAGOCYTOSIS IN RABBITS AFTER WHOLE-BODY Co$sup 60$ IRRADIATION

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