RECRUITMENT AND RECIRCULATION OF LEUKOCYTES AFTER AN ULTRAMARATHON RUN - PREFERENTIAL HOMING OF CELLS EXPRESSING HIGH-LEVELS OF THE ADHESION MOLECULE LFA-1

The alpha(L) beta(2) (CD11a/CD18) integrin LFA-1 (lymphocyte function- associated antigen-1) mainly contributes to the firm arrest of leucocy tes on the endothelium. Its cell surface density is thought to be impo rtant for the exercise-induced homing of leucocytes. 9 athletes (7 mal es, 2 females, age 36-68 years, body mass 64+/-10 kg, height: 175+/-10 cm) absolved a competitive 100 km run in 8:07 hours (range: 7:29-9:50 hours). Immunophenotyping of circulating leucocytes and data aquisiti on by three colour flow cytometry before and up to 3 hours after the r ace showed that post exercise lymphocyte subpopulations with a higher expression of CD11a like CD3(+)CD8(+)CD45RO(+) T-cells, natural killer cells (CD3(-)CD16/CD56(+)) and cytotoxic, not MHC-restricted T-cells (CD3(+)CD16/CD56(+)) decreased significantly more than CD45RO(+) and C D45RO(-) helper-T-cells (CD3(+)CD4(+)), CD3(+)CD8(+)CD45RO(-) T-cells and B-cells (CD19(+)), which have lower levels for CD11a. Cell concent rations of regular monocytes (Fc gamma receptor 3 negative, LFA-1 low positive) increased whereas mature monocytes (Fc gamma receptor 3 low or high positive respectively, LFA-1 high positive) decreased. In conc lusion the surface density of the adhesion molecule LFA-1 on leucocyte s is likely to contribute significantly to the extent of leucocyte's h oming after long endurance exercise.