Effects of spaceflight on rat peripheral blood leukocytes and bone marrow progenitor cells

Abstract: The white blood cell (WBC) elements and the bone marrow myeloid progenitor cell populations were analyzed to ascertain adaptation to micro-gravity and subsequent readaptation to 1 G in rats flown on the 14-day Spacelab Life Sciences-2 (SLS-2) mission. Bone marrow cells were harvested from one group of rats killed inflight (FD13) and blood was drawn from three other groups at various times. The WBC level was normal on FD14 with the excep-tion of neutrophilia. On FD13, numbers of colony-forming units-granulocyte (CFU-G), CFU-GM, and CFU-M from flight animals were decreased corn-pared with ground controls when incubated with recombinant rat interleukin-3 (rrIL-3) alone or in combination with recombinant human erythropoie-tin (rhEpo). On recovery (R + 0), flight rats had decreased numbers of total leukocytes and absolute numbers of lymphocytes and monocytes with ele-vated neutrophils compared with control rats. They had lower numbers of CD4, CD8, CD2, CD3, and B cells in the peripheral blood but no differences i