Fig. 1. Percentage of change in number of circulating leukocytes and levels of catecholamines among 11 astronauts after landing (R+0) as compared with preflight (L-10) values. After landing, the number of neutrophils (Neu), monocytes (Mon), CD3⁺CD4⁺ T-helper cells (CD4), CD19⁺ B cells (CD19), and plasma norepinephrine (NE) levels were significantly elevated, whereas the number of NK cells was significantly decreased (p values < .05). Mixed lymphocytes (Lym), eosinophils (Eos), CD3⁺CD8⁺ T-cytotoxic cells (CD8), and plasma epinephrine (Epi) were not significantly changed.