Neopterin, a pteridine compound produced by macrophages activated by i
nterferon-gamma, is widely used to assess the activation of cellular i
mmunity. An elevation in serum or urinary neopterin reflects immune ac
tivation in many different disorders, including viral infections, canc
er, autoimmune diseases or acute myocardial infarction, but less atten
tion has been paid to neopterin concentration in other biological flui
ds. The aim of the present study was to examine neopterin concentratio
n in gastric juice. An association with the presence of Helicobacter p
ylori, a bacterium linked to the most common disorders of upper digest
ive tract, was also investigated. Gastric juice was obtained at endosc
opy from 61 patients. Neopterin was determined by a radioimmunoassay a
nd the presence of H. pylori was examined by urease test. The macrosco
pic finding of bile in gastric juice was associated with significantly
higher neopterin levels compared to patients where no bile was noted
(15.5 +/- 15.6 vs. 2.1 +/- 3.0 nmol/l, P < 0.001). However, similar co
ncentrations were observed in the H. pylori positive and H. pylori neg
ative patients (7.6 +/- 12.0 vs. 11.1 +/- 14.9 nmol/l). Even in the ab
sence of macroscopic bile contamination, no significant difference cou
ld be found between the infected and uninfected patients (2.3 +/- 3.2
vs. 1.3 +/- 1.9 nmol/l), and the patients with duodenal ulcer and norm
al findings (3.8 +/- 4.6 vs 1.6 +/- 1.9 nmol/l). The contamination of
gastric juice with bile represents the limitation for the use of neopt
erin as a marker of immune activation in the gastric mucosa. Rather th
an an index of immune activation, gastric juice neopterin concentratio
n represents a marker of duodenogastric reflux.