title: Effect of environmental enrichment and housing density on immune system reactivity to acute exercise stress.
abstract: Positive stress has been described in the literature but not well characterized experimentally. This experiment was designed to test the hypothesis that environmental enrichment and housing density in C57BL/6 female mice modulate immune responses to acute exercise stress. A 2 x 2 x 2 factorial design was used where enrichment (enrich), nonenriched (nonenrich), group housed (group), individually housed (ind), and stress (stress) or no stress (nonstress) acted as the independent variables. Enrichment involved a 7-week exposure to in-cage running wheels and a variety of cage objects. Ninety minutes after treadmill exercise stress at 25 m/min, 4 degrees slope, for 30 min (or no exercise stress) mice were sacrificed, and splenocyte blastogenesis to the T-cell mitogen concanavalin A (Con A), splenic T-cell subset enumeration, and percent live/dead splenic cells by flow cytometry were evaluated. Results showed significant interaction effects for mitogen responses, percent Ly2+ subset, and percent live/dead splenocyte responses. Proliferation to Con A was higher in nonenrich group-housed animals than other groups. Percent live/dead cell analysis revealed a significant housing x stress interaction with fewer percent live and higher percent metabolically stressed splenocytes obtained from ind-stressed mice than other groups. These data suggest that enrichment and housing density are important factors influencing immune responses in the basal state, and in response to exercise stress.
authors.affiliation: Department of Health Studies and Gerontology, University of Waterloo, Ontario, Canada.
authors.forename: S G
authors.initials: SG
authors.lastname: Kingston
authors.forename: L
authors.initials: L
authors.lastname: Hoffman-Goetz
mesh_terms: D000818:Animals; D001143:Arousal / Q000502:physiology*; D005260:Female; D007108:Immune Tolerance / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D018655:Lymphocyte Count; D051379:Mice; D008810:Mice, Inbred C57BL; D005082:Physical Exertion / Q000502:physiology*; D011598:Psychoneuroimmunology; D012016:Reference Values; D012931:Social Environment; D013315:Stress, Psychological / Q000150:complications* / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology*