L-deprenyl-induced increase in IL-2 and NK cell activity accompanies restoration of noradrenergic nerve fibers in the spleens of old F344 rats

Previously, we have hypothesized a causal relationship between some measure s of immunosenescence and the age-related decline in sympathetic noradrener gic (NA) nerve fibers in spleen and lymph nodes of F334 rats. In the presen t study, we investigated this interrelationship further by measuring NK cel l activity, Con A-induced IL-2 production, norepinephrine (NE) concentratio n, and morphological localization of NA and neuropeptide-Y (NPY) nerve fibe rs in the spleens of old (21 months old) male F344 rats after 10 weeks of d aily treatment with low doses of L-deprenyl, an irreversible monoamine oxid ase-B inhibitor, followed by a 9-day wash-out period, NK cell activity and Con A-induced IL-2 production were increased in deprenyl-treated old rats i n comparison to untreated and saline-treated old rats. Deprenyl treatment d id not alter the percentage of CD5 + T-cells, but moderately increased the percentage of sIgM(+) B-cells in the spleens of old rats. In addition to ch anges in immune responses, NE content and the volume density of NA and NPY nerve fibers were partially augmented in the spleens of deprenyl-treated ol d rats. In a separate study, various concentrations of deprenyl were added in vitro to spleen cells from young and old F334 rats to examine the direct effects of the drug on Con A-induced n-2 production. In contrast to in viv o treatment, in vitro addition of deprenyl did not alter the Con A-induced IL-2 production by splenocytes from old rats. Together, these results sugge st that the ability of deprenyl to enhance certain immune responses are int erlinked to the restoration of sympathetic NA and NPY nerve fibers in the s pleens of old rats. (C) 1998 Elsevier Science B.V. All rights reserved.