Exposure of rats to 600 r total body radiation did not influence either the rate or the extent of migration of their leucocytes 1 day after irradiation, but did decrease their migration on the 2nd and the 5th postirradiation day. Migration of rat leucocytes was not altered by infection of the animal with M. aureus.
Leucocytes of rabbits irradiated with 100 r showed a normal rate and extent of migration. However rabbits exposed to 500 r or 800 r showed depression of leucocyte migration at two postirradiation intervals, on the 3rd to 5th and the 10th to 13th days after irradiation, with normal activity intervening. By the 21st postirradiation day the ability of leucocytes to migrate returned to normal. The effect of radiation on total and differential W.B.C. counts and the relationship of this effect to migration is discussed.
The decrease in leucocyte migration could not be ascribed either to leucopenia or to plasma factors.