Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 53, Issue 6 B430-B437, Copyright © 1998 by The Gerontological Society of America
Effects of maximal exercise on natural killer (NK) cell cytotoxicity and responsiveness to interferon-alpha in the young and old
JA Woods, JK Evans, BW Wolters, MA Ceddia and E McAuley
Department of Kinesiology, University of Illinois at Urbana/Champaign, Urbana 61801, USA. [email protected]
We investigated the effects of a graded maximal exercise treadmill test on
natural killer (NK) cell number, activity, and responsiveness to
interferon-alpha (IFN-alpha) in young (22+/-0.7 yrs) and elderly (65+/- 0.8
yrs) sedentary subjects. NK cell cytotoxicity (NKCC) was determined using
Ficoll purified peripheral blood mononuclear cells (PBMCs) by a 51Cr
release assay against NK-sensitive (K562) and NK-insensitive (Daudi) target
cells at various effector:target (E:T) ratios before and immediately after
exercise. PBMCs were incubated with rhu IFN-alpha (125 and 250u/10(6)
PBMCs) or without for 2 hrs before addition to the 51Cr release assay.
There were no differences in unstimulated NKCC against K562 or Daudi
targets between the old and the young despite significantly (p=.01) higher
percentages of CD56+ NK cells (21.1+/-2.3% in old vs 12.5+/-2.5% in young,
pre-exercise). IFN-alpha increased NKCC versus both targets, and NK cells
from old subjects were hyporesponsive to IFN-alpha stimulation; this was
especially evident at low E:T ratios versus Daudi cells. Maximal exercise
significantly increased (50-200%) unstimulated NKCC versus K562 and Daudi
targets similarly in both young and old and increased the percentage of
CD56+ cells in the PBMC fraction to 33.3+/-3.7% and 23.3+/-3.6% in old and
young, respectively. We found a significant correlation between %CD56+ and
basal NKCC versus K562s and Daudi cells in the young (i.e., r=.55; p=.02 vs
K562s), but not the old (i.e., r=.20; p=.29 vs K562s) subjects. This
indicates that, in the young, part of the exercise-induced increase in NKCC
is due to an increase in NK cell number. Maximal exercise did not affect
unstimulated per cell killing of K562s, but tended to increase per cell
killing of Daudis. These results indicate that CD56+ cells from old
subjects have an intrinsic defect in their ability to perform cytolysis and
respond to IFN-alpha. Furthermore, a single bout of maximal exercise
increases NKCC and CD56+ cell number similarly in both young and old
subjects regardless of the target cell used.
