The objective of this study was to assess the potential immunomodulatory effect of six Lactobacillus strains on human peripheral blood mononuclear cells (hPBMC) isolated from allergic patients. hPBMC from patients allergic to birch pollen or grass pollen were cultured in vitro in the presence or absence of selective bacterial strains. Cultures were left unstimulated or stimulated with αCD3/αCD28 or Bet v 1. After 1, 4 and 8 days, cells and culture supernatants were harvested and the effect on cellular proliferation and the supernatant levels of several cytokines was assessed. All strains had the ability to repress IL-13 production but did show a differential effect on IFN-γ induction. Both strains B223 and B1697 showed a lower IFN-γ, IL-12 and TNF-α induction as compared with the other tested strains. Strain B633 showed the best proliferation-suppressive properties in αCD3/αCD28-stimulated cells. Suppression of the T-helper type 2 (Th2) cytokine induction and induction of the Th1 cytokine production by specific strains might be beneficial for allergic patients having a disturbed Th1/Th2 immune balance. Furthermore, hPBMC of patients with seasonal allergy outside the pollen season can be used to determine the immunomodulatory activities of probiotic bacteria.
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