NO MANDATORY ROLE FOR THE SPLEEN IN THE EXERCISE-INDUCED LEUKOCYTOSISIN MAN

1. Short-lasting strenuous physical exercise leads to a marked increas e in the blood concentration of leucocytes in healthy humans. The cell sources of this leucocytosis have not been definitely identified, nei ther has the contribution made by the various subtypes of leucocytes. 2. We have compared the exercise-induced leucocytosis in six splenecto mized and six intact subjects. The blood concentrations of leucocytes as well as of most subtypes, except monocytes and eosinophilic granulo cytes, increased substantially at the end of a 5 min exercise (200 W) bout. 3. The increases were similar in the splenectomized subjects and in the control subjects. Thirty minutes after completion of the exerc ise the various leucocyte blood concentrations had returned to pre-exe rcise levels. 4. The plasma concentrations of several cytokines (inter leukins-1 alpha and -6; tumour necrosis factor-alpha and granulocyte c olony-stimulating factor) known to affect leucocyte kinetics did not c hange appreciably with exercise in either group. 5. We conclude that e xercise-induced leucocytosis can take place in the absence of the sple en. There was no evidence that cytokines known to affect leucocyte for mation, mobilization and activity are involved in this leucocytosis.