Do Circulating Leukocytes and Lymphocyte Subtypes Increase in Response to Brief Exercise in Children With and Without Asthma?

Christina D Schwindt ¹, Frank Zaldivar ¹, Lori Wilson ¹, Szu-Yun Leu ¹, Jessica Wang-Rodriguez ², Paul J Mills ³ and Dan M Cooper ^1*

¹ University of California, Irvine, United States
² Univeristy of California, San Diego and VA San Diego Healthcare Systems, United States
³ Univeristy of California, San Diego, United States

^* To whom correspondence should be addressed. E-mail: dcooper{at}uci.edu.

Accepted 18 September 2006

Abstract

Background: Exercise can alter health in children in both beneficial (e.g., reduced longterm risk of atherosclerosis) and adverse (e.g., exercise induced asthma) ways. The mechanisms linking exercise and health are not known, but may rest, in part, on the ability of exercise to increase circulating immune cells. Little is known about the impact of brief exercise, more reflective of naturally occurring patterns of physical activity in children, on immune cell responses.

Objective: To determine: 1) if a 6-min bout of exercise can increase circulating inflammatory cells in healthy children; and 2) if the impact of brief exercise is greater in children with a history of asthma.

Methods: Children with mild-moderate persistent asthma (A) and age-matched controls (C) [n=14 in each group, mean age 13.6 y.o.] performed a 6-min bout of cycle-ergometer exercise. Spirometry was performed at baseline and following exercise. Blood was drawn at pre- and post-exercise, leukocytes were quantified, and key lymphocyte cell surface markers were assessed by flow cytometry.

Results: Exercise decreased spirometry only in asthmatics, but increased (p<0.001) most types of leukocytes [e.g., lymphocytes (C, 1210±208 cells/µl; A, 1119±147 cells/µl) and eosinophils (C, 104±22 cells/µl; A 88±20 cells/µl)] to the same degree in both groups. Similarly, exercise increased T-helper cells (C, 248±60 cells/µl; A, 232±53 cells/µl) and most other lymphocyte subtypes tested. In contrast, although basophils (16±5 cells/µl) and CD4+CD45RO+RA+ lymphocytes (19±4 cells/µl) increased in controls, no increase in these cell types was found in asthmatics.

Conclusions: Exercise increased many circulating inflammatory cells in both asthmatics and controls. Circulating inflammatory cells did increase in asthmatics but not to a greater degree than in controls. In fact, basophils and T-helper lymphocyte memory transition cells did not increase in asthmatics while they did increase in controls. Even brief exercise in children and adolescents robustly mobilizes circulating immune cells.

Key Words: asthma, children, exercise, leukocytes, lymphocyte subsets

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