Abstract
Immunophenotyping by dual parameter flow cytometry was used to compare the expression
of interleukin-2 receptor α and β chains on lymphocyte subsets in the peripheral blood
of 7 trained and 6 untrained volunteers (respective V̇O2max 57.0±6.1 and 39.0±4.5ml·kg-1 · min-1). Venous blood samples were collected at least 36 h after the most recent exercise
session. The trained subjects had higher circulating counts (109 · 1-1) of total leukocytes (5.80±0.83 vs. 4.63±0.21, p<0.05), granulocytes (3.14±0.72 vs.
1.90±0.30, p<0.05), and NK cells (CD16+ 0.32±0.14 vs. 0.16±0.05, p<0.05; CD56+, 0.41±0.14 vs. 0.21±0.03, p<0.01), but lower lymphocyte counts than their sedentary
peers (1.90±0.22 vs. 2.26±0.25, p<0.05). Counts for T cells (CD3+) and B cells (CD19+), and the CD4+/CD8+ ratio did not differ between the two subject groups.
The p55-IL-2 receptor α expression (CD25+: 0.63±0.11 vs. 0.69±0.17) was unrelated to training, but the p70-75-IL-2 receptor
β expression was higher in the active group (p70/Mik-β1
+: 0.42±0.09 vs. 0.20±0.06, p<0.001; p75/TU27+: 0.36±0.08 vs. 0.17±0.07, p<0.005). Beta chain co-expression was also higher on NK
cell subsets (p<0.001) in trained than in sedentary subjects. Aerobic power was strongly
correlated with IL-2Rβ expression (r = 0.914, p<0.001 for Mik-β1; r = 0.884, p<0.005 for TU27). We conclude that physical conditioning is associated
with an increase in IL-2 receptor β expression on lymphocytes as assessed by the proportion
of circulating p70-75-IL-2Rβ positive NK cells. Such changes could enhance protection
against both infectious diseases and cancer. Longitudinal studies are now needed to
explore the causal nature of this association.
Key words
Aerobic power - cytokines - cancer - immune function - natural immunity - training
