We recently found that dietary
raffinose suppressed allergic airway
eosinophilia in
ovalbumin-sensitized Brown Norway rats. Using this model in the present study, we compared the efficacy of other
oligosaccharides with that of
raffinose. Brown Norway rats were immunized s.c. with
ovalbumin on d 0 and exposed to aerosolized
ovalbumin on d 20; broncho-alveolar lavage fluid was obtained on d 21. In Expt. 1, rats were fed a control diet or diets supplemented with different
oligosaccharides (50 g/kg diet,
raffinose, alpha-linked galactooligosaccharide,
fructooligosaccharide, and
xylooligosaccharide). The number of eosinophils in the fluid was significantly lower in rats fed
raffinose and alpha-linked galactooligosaccharide diets than in those fed the control diet. Dietary
fructooligosaccharide and
xylooligosaccharide did not affect airway
eosinophilia. In Expt. 2, i.p. administration of
raffinose and alpha-linked galactooligosaccharide, but not
fructooligosaccharide and
xylooligosaccharide, suppressed airway
eosinophilia in rats fed the control diet. In Expt. 3, suppression of airway
eosinophilia by dietary alpha-linked galactooligosaccharide occurred in cecectomized rats administered
neomycin. Reduced levels of
interleukin (IL)-4 and
IL-5 mRNA in lung tissue were associated with the suppression of airway
eosinophilia. We propose that indigestible
oligosaccharides differ in their suppressive effect on allergic airway
eosinophilia in
ovalbumin-sensitized Brown Norway rats and that the effect appears not to be mediated by intestinal microflora.