Disease outcomes as a consequence of environmental influences on the development of the immune system.

PURPOSE OF REVIEW: To review recent studies on disease outcomes as a consequence of environmental influences on the developing immune system early in life.

RECENT FINDINGS: The increasing incidence of 'immunologically mediated disease of affluence', such as allergies, type I diabetes and inflammatory bowel disease (IBD), suggests that they are consequences of common environmental factors. No such factors have been identified, however, and prospective studies fail to support commonly given advice. Interest has, therefore, switched towards factors that could induce and maintain tolerance to allergens and autoantigens. A unifying link between Th1-dependent autoimmune disease and Th2-linked atopic allergy would be a disturbed immune regulation involving T regulatory cells. Microbial colonization of the gastrointestinal tract, linked with lifestyle, may be an important determinant. Several prospective, controlled studies, in which different strains of Lactobacillus were given to pregnant mothers and then to their newborn babies for 6-12 months, have shown a modest reduction of immunoglobulin E (IgE)-mediated eczema in infants.

SUMMARY: Currently, there is poor support for giving any particular allergy-preventive advice. Novel potential strategies to enhance immune regulation and tolerance induction include modulation of gut microbiota, for example, by probiotics and prebiotics. Although the results are somewhat encouraging, they are insufficient to base general recommendations on, however.