In vitro studies suggest that OO is more immune-neutral
compared to other lipid emulsions. For instance, SO-induced inhi-
bition of T cell proliferation, -activation and migration, was not
observed after OO exposure, and OO was less potent in inhibiting
inflammatory cytokine production by PBMCs and inducing leuko-
cyte death. 13e15 Furthermore, emulsions based on OO have been
shown to modify neutrophil responses in vitro to a lesser extent
than emulsions based on SO or mixed SO and medium chain
triglycerides (MCTs). 16 These immune-neutral effects of OO have
been confirmed in animal studies. 17,18 Data on immune modulation
by OO-based emulsions in vivo are, however, sparse. Clinical trials
included patients with several pathologies, and in vivo studies in
healthy volunteers mostly concerned small short-term trials with
low power. These studies mainly focused on safety and efficacy and
did not provide any detailed insight into immune modulating
properties of OO-based lipids. 19e26 Concerning the evaluation of
immune modulation, only plasma inflammatory markers (C-reac-
tive protein and cytokine-levels) and plasma oxidative stress
markers were assessed. With respect to oxidative stress, our group
has previously shown that long-term HPN use does not seem to
result in significant oxidative damage or an altered oxidante
antioxidant balance in a group of 41 Dutch HPN patients, of
whom 75% were using a OO-based emulsion. 9 In contrast to most
clinical trials, in the present study the activation and function of
leukocytes (mainly neutrophils) in HPN patients and healthy
controls were assessed by multiple assays.