The effects of intensive, moderate and downhill treadmill running on human blood lymphocytes expressing the adhesion/activation molecules CD54 (ICAM-1), CD18 (β₂ integrin) and CD53

Abstract

This study examined the effects of intensive, moderate and downhill treadmill running on blood lymphocyte expression of adhesion/activation (AA) molecules. Trained subjects completed three treadmill-running protocols of identical duration: (1) an intensive protocol at 80% $\ifmmode\expandafter\dot\else\expandafter\.\fi{V}_{{{\text{O}}_{{2\max }} }}$ to volitional exhaustion, (2) a moderate protocol at 60% $\ifmmode\expandafter\dot\else\expandafter\.\fi{V}_{{{\text{O}}_{{2\max }} }}$ and (3) a −10% downhill (eccentric) protocol at 80% $\ifmmode\expandafter\dot\else\expandafter\.\fi{V}_{{{\text{O}}_{{2\max }} }}$. Blood samples were taken before, immediately after, 1 and 24 h after exercise. Isolated lymphocytes were assessed for expression of the AA molecules CD54, CD18 and CD53 by flow cytometry. Lymphocyte counts increased immediately after all running protocols. Lymphocytopenia was observed 1 h after the intensive and eccentric protocols only. Plasma creatine kinase increased 24 h after the downhill protocol only. Increases in the number and percentage of CD54⁺, CD18^bright and CD53^bright lymphocytes were observed immediately after the intensive and eccentric protocols, with the numbers falling below pre-exercise values at 1 h post-exercise for all protocols. No differences were found between the intensive protocol and the eccentric protocol at the same relative intensity. Analysis of lymphocyte subsets showed that the total number of CD3⁺, CD4⁺, CD8⁺ and CD56⁺ lymphocytes increased after the intensive protocol before falling below pre-exercise values at 1 h post-exercise. A relatively greater mobilisation of CD56⁺ and CD8⁺ cells accounts for the changes in CD54⁺, CD18^bright and CD53^bright cell populations. Lymphocytes that enter and exit the circulation following exercise express high levels of AA molecules, which may mediate extravasation and post-exercise lymphocytopenia. This effect appears to be influenced by exercise intensity and not muscle damage.