Mood change and immune status of human subjects in a 10-day confinement study.

INTRODUCTION: Stress is a known factor that causes changes in leukocyte distribution or depression in lymphocyte proliferation. We reported previously that a 10-d confinement caused changes in immune status. Here we report the relationship between mood changes and immune parameters in the subjects confined for 10-d.

METHODS: There were 10 subjects (age 20-27 yr, mean 22.8 yr) who participated in a 10-d confinement study. They were divided into 2 groups with regard to their psychological aspects and their immune parameters were then compared. Blood samples were taken once before, three times during, and once after confinement. The percentages of granulocytes, natural killer (NK) cells, and cells positive for CD69, an early activation marker, were analyzed by flow cytometry. Face scale was employed to estimate subjects' mood.

RESULTS: The group that showed an increase in mood scale toward the end of the confinement showed changes in all immune parameters. In contrast, less marked changes were seen in the group that showed no mood changes throughout the experiment.

DISCUSSION: These results indicate that the observed immune changes were related to the mood changes, and that mood change seems to be one of the causes of the immunological changes seen in confined environments, such as in space stations or submarines. The percentages of NK cells, granulocytes, and CD69 expression may be useful criteria for detecting immunological deterioration caused by stress, or for selecting astronauts who are immunologically stable against the challenge of confinement stress.