Abstract
The present study was designed to explain the mechanism of the post-exercise down-regulation
of human natural killer (NK) cell activity recently described by us. Fifteen young,
healthy volunteers underwent 60 min of bicycle exercise at 75% of maximal oxygen uptake
(VO2max). Six of the volunteers were exercised twice with an interval of at least one month.
At the second exercise test they received oral indomethacin. Blood samples were collected
before and during the last minutes of exercise as well as 2 h and 24 h after work.
The NK cell activity (lysis fixed number of mononuclear cells) increased during bicycle
exercise, dropped to a minimum 2 h later and returned to pre-exercise levels within
24 h. During bicycle exercise the percentage of NK cells (CD 16 + cells) of mononuclear
cells increased significantly but returned to normal within 2 h after exercise. Two
hours after exercise, however, increased monocyte cell count and neutrophils were
found. The in vitro release of prostaglandin E2 from mononuclear cells was increased.
Furthermore, the neutrophil chemiluminescence response was also increased in the 2
h post-exercise period; this response is associated with prostaglandin E2 production
by neutrophils. Indomethacin, whether administered in vivo or in vitro, fully restored
the suppressed post-exercise NK cell activity. Finally, the NK cell activity of monocyte
depleted mononuclear cells did not decrease below basal levels after exercise. These
findings strongly indicate that prostaglandins released from monocytes and neutrophils
are involved in the post-exercise down-regulation of NK cells.
Key words
Natural killer cells - exercise - monocytes - neutrophils - indomethacin - prostaglandin
