Importance of intestinal colonisation in the maturation of humoral immunity in early infancy: a prospective follow up study of healthy infants aged 0-6 months

Abstract

AIM To evaluate the role of intestinal microflora and early formula feeding in the maturation of humoral immunity in healthy newborn infants. STUDY DESIGN Sixty four healthy infants were studied. Faecal colonisation withBacteroides fragilis group,Bifidobacterium-like, andLactobacillus-like bacteria was examined at 1, 2, and 6 months of age, and also the number of IgA-secreting, IgM-secreting, and IgG-secreting cells (detected by ELISPOT) at 0, 2, and 6 months of age. RESULTS Intestinal colonisation with bacteria from the B fragilis group was more closely associated with maturation of IgA-secreting and IgM-secreting cells than colonisation with the other bacterial genera studied or diet. Infants colonised withB fragilis at 1 month of age had more IgA-secreting and IgM-secreting cells/10⁶ mononuclear cells at 2 months of age (geometric mean (95% confidence interval) 1393 (962 to 2018) and 754 (427 to 1332) respectively) than infants not colonised (1015 (826 to 1247) and 394 (304 to 511) respectively); p = 0.04 and p = 0.009 respectively. CONCLUSIONS The type of bacteria colonising the intestine of newborns and the timing may determine the immunomodulation of the naive immune system.