title: Natural killer cell activity during head-up tilt-induced central hypovolemia in humans.
abstract: Changes in immunological competent blood cells were evoked in seven humans during passive head-up tilt (50 degrees anti-Trendelenburg's position maintained until appearance of presyncopal symptoms). Blood samples were collected after 60 min of rest, when presyncopal symptoms appeared during tilt, and 105 min after tilt-down. Natural killer (NK) cell activity increased during head-up tilt due to a three to four-fold increase in CD16+ NK cells in blood. In support NK cell activity boosted with interferon-alpha and interleukin 2 (IL-2) rose in parallel with unboosted NK cell activity. This effect on NK cells disappeared during recovery but was not suppressed when compared to prevalues. Lymphocyte concentration also increased during head-up tilt. Concentrations of CD3+ and CD4+ T cells were almost stable during head-up tilt, whereas the percentage of CD3+ T cells in relation to blood mononuclear cell (BMNC) concentration decreased, due to a diminished percentage of CD4+ T cells and the marked simultaneous increase in the percentage of CD16+ NK cells. Although changes in the BMNC composition occurred, the proliferative responses of BMNC following stimulation with phytohemagglutinin, purified derivative of tuberculin, or IL-2 did not change significantly. We conclude that head-up tilt induced marked changes in subpopulations of BMNC, especially the CD16+ NK cells, as they were recruited to the blood.
authors.affiliation: Danish Armed Forces Health Services, Jaegersborg.
authors.forename: M
authors.initials: M
authors.lastname: Klokker
authors.forename: N H
authors.initials: NH
authors.lastname: Secher
authors.forename: S
authors.initials: S
authors.lastname: Matzen
authors.forename: B K
authors.initials: BK
authors.lastname: Pedersen
mesh_terms: D000328:Adult; D015703:Antigens, CD; D001810:Blood Volume / Q000502:physiology*; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D007958:Leukocyte Count; D008213:Lymphocyte Activation; D016131:Lymphocyte Subsets; D008297:Male; D011187:Posture / Q000502:physiology*
chemical_list: D015703:Antigens, CD