Immune Effects
It is now firmly established that opioids influence immune regulation.
Direct effects of opioid agonists include modulation of immune cellular activity,
as well as that of specific enzymatic degradation and regulation processes.[289]
Several immune cell populations, including T cells, macrophages and natural killer
(NK) cells, serve as targets for the effects of opioids. It was shown that the maximal
effect on NK cell activity, proliferation of splenic T and B cells and interferon-γ
production are observed 0.5 to 1 hour after 15 mg/kg morphine injection in rats.
[290]
The time course was nearly concordant with
that of the antinociceptive effect of morphine. Postoperative administration of
morphine (10 mg IM) or tramadol (100 mg IM) induced different changes in NK cell
activity.[291]
More recently, it was reported that
intravenously administered
fentanyl causes a rapid increase in NK cell cytotoxicity, which was coincident with
an increase in the percentage of CD16+
and CD8+
cells in peripheral
blood.[292]
As a potential mechanism for the immunosuppressive
effects of opioids, it was demonstrated that NF-κB activation induced by an
inflammatory stimulus was inhibited by morphine in a nitric oxide-dependent manner.
[293]
