Enhanced Expression of HLA-DR, Fcγ Receptor 1 (CD64) and Leukocyte Common Antigen (CD45) Indicate Activation of Monocytes in Regenerative Training Periods of Endurance Athletes

The aim of this study was to test the hypothesis whether endurance athletes have distinct expressions of functionally relevant surface antigens of monocytes. Under standardized experimental and laboratory conditions CD14⁺ blood monocytes of 55 males (22 sedentary controls [CO], individual anaerobic threshold [IAT]: 2.2 ± 1.2 W · kg^-1, VO₂max: 47 ± 12 ml · min^-1 · kg^-1; 13 endurance athletes, training: 3 - 10 hours weekly [E1], IAT: 3.0 ± 1.1 W · kg^-1, VO₂max: 57 ± 5 ml · min^-1 · kg^-1; 20 endurance athletes training: >10 hours weekly [E2], IAT: 3.7 ± 1.3 W · kg^-1, VO₂max: 64 ± 6 ml · min^-1 · kg^-1) were investigated for relative surface receptor expression of CD45, CD64 and HLA-DR (direct immunofluorescence, flow cytometry). E₁ and E₂ showed significantly (ANOVA, Tukey's HSD test; each p < 0.01) higher relative receptor expressions for CD64 in comparison to CO (E₁: + 62/E₂: + 71 %; percentage of increase compared to CO value), CD45 (+ 44 /+ 31 %) and HLA-DR (+ 22/+ 35 %). Cell counts off four monocyte subpopulations (CD56⁺. CD14^bright+ CD16⁺, CD14^bright+ CD16^dim+, CD14^dim+ -CD16^bright+) did not show significant differences between the groups. These data suggest that in endurance athletes during regenerative training period circulating monocytes show an enhancement of functionally relevant surface receptors indicating an activation of monocytes.

Monocytes - surface antigens - athletes - endurance training - exercise - flow cytometry - immunophenotyping