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P. KEITH, Dept. of Medicine, McMaster Univ., Div. of Immunology/Allergy, 1200 Main St. W., HSC-3V48, Hamilton, ON L8N 3Z5, Canada In the last few decades, industrialized countries have witnessed a distressing rise in the prevalence of atopy. Because this epidemiological trend has emerged during an era of improved hygiene and successful control of infection, researchers believe that the decrease in atopy is Ftiologically linked to decreased exposure to microbial agents. It has been convincingly demonstrated that infection can modulate the incidence of allergic disorders, possibly through the elicitation of Th1-polarized phenomena that subvert the Th2 character of atopy. Intestinal flora, both pathogenic and commensal, show a similar ability to modulate the local immunological environment, and this local modulation can influence systemic immunological events. The mechanisms by which this immune conditioning occurs have yet to be elucidated, but the clinical implications seem clear: probiotics, which exploit the prophylactic effects of live microbial food ingredients, are now being explored with growing interest as a bonafide therapeutic option in the management—and even primary prevention—of allergic diseases. A recent double-blind, randomized, placebo-controlled trial in which lactobacilli were given prenatally to mothers with high risk for atopic eczema, allergic rhinitis or asthma, and then postnatally for six months to their infants found that the frequency of atopic eczema in the probiotic group was half that of the placebo. The reduced risk of eczema was still seen in the infants at 4 years of age suggesting a long lasting effect of this early intervention. Irrespective of inconclusive mechanistic details, probiotics represent a therapeutic paradigm that, unlike conventional modalities, attends to the epidemiology, and possibly the Ftiology, of atopy. For this reason, probiotic intervention during infantile microbial colonization of the gut—and the articulation of an intrinsic immunologic “disposition” antithetical to Th2 polarization—may be a realistic consideration for primary prevention of allergy and asthma.
Session 24, Probiotics in health: Their potential against allergic diseases
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