Leukapheresis in Man. III. Hematologic Observations in Patients with Leukemia and Myeloid Metaplasia

Eleven patients with leukemia and one patient with myeloid metaplasia underwent leukapheresis on 18 occasions for 94 to 275 minutes during which 93 to 1668 x 10⁹ leukocytes were removed. All patients exhibited a significant and continued decline of peripheral leukocyte concentration during or after the procedure. In 12 of the 18 instances, the leukocyte concentration returned slowly to the initial leukocyte level within 1 hour to 22 days. The number of leukocytes withdrawn represented 16 to 247 per cent of the initial circulating volume removed at a rate of 0.13 to 1.14 leukocyte blood volumes per hour. The RAR was 1:1 to 12:1 to the circulating leukocyte number. Rate of replenishment of the circulating immature leukocyte numbers were 4.0 x 10⁷ to 52.2 x 10⁹/Kg./day. The PMN’s were replaced at rates of 10 x 10⁶ to 7.05 x 10⁹/Kg./day which were equal to or slower than in normal subjects. Changes in number occurred in the dominant leukemic cell types without significant shifts in the differential counts. No changes in marrow population other than a slight decrease in cellularity were observed.

The data indicate that in the leukemic patient the peripheral leukocyte concentration was not maintained or replenished promptly following the withdrawal of sizeable quantities of leukocytes, demonstrating a block in transfer of leukocytes from the tissues to the blood. This is in marked contrast to the leukocytosis and marrow stimulation observed in hematopoietically normal subjects following leukaphereses.

The platelet counts fell promptly during leukapheresis, returning toward control levels in eight studies within 7 hours following the procedure. In four studies the platelet counts returned to control levels in 3 to 9 days. The changes in platelet concentrations were similar to those observed with hematologically normal subjects. The size of the platelet reservoir in these leukemic patients is about twice that of the circulating blood.