ATOPIC VERSUS INFECTIOUS-DISEASES IN CHILDHOOD - A QUESTION OF BALANCE

There is an increasing interest in the concept that respiratory tract infections during early childhood may in some circumstances confer pro tection against sensitisation to aeroallergens, via ''bystander'' stim ulation of Th-l associated immune functions in the regional lymph node s draining the airway mucosa. We hypothesise below that this phenomeno n may be but one component of a broader process operative during early postnatal life, in which generalised contact with the microbial envir onment plays an obligatory role in stimulating the functional maturati on of the Th-l arm of the immune response. We argue further that one o f the most potent sources of such stimulation is provided by the norma l commensal flora of the gastrointestinal tract, which is establish du ring early infancy.