Allergic disease in 8-year-old children is preceded by delayed B cell maturation.

BACKGROUND: We previously reported that exposure to a farming environment is allergy-protective, while high proportions of neonatal immature/naïve CD5+ B cells and putative regulatory T cells (Tregs) are risk factors for development of allergic disease and sensitization up to 3 years of age. OBJECTIVE: To examine if B and T cell maturation are associated with allergic disease and farming environment over the first 8 years in life. METHODS: In the prospective FARMFLORA study, including both farming and non-farming families, 48 of 65 children took part in the 8-year follow-up study. Various B and T cell maturation variables were examined in blood samples obtained at several occasions from birth to 8 years of age and related to doctors' diagnosed allergic disease and sensitization, and to farming environment. RESULTS: We found that the incidence of allergic disease was lower among farmers' compared to non-farmers' children during the 8-year follow-up period, and that farmers' children had higher proportions of memory B cells at 8 years of age. Moreover, a high proportion of neonatal CD5+ B cells was a risk factor for and may predict development of allergic disease at 8 years of age. A high proportion of Tregs was not protective against development of these conditions. CONCLUSION AND CLINICAL RELEVANCE: High proportions of neonatal naïve B cells remained as a risk factor for allergic disease in school-aged children. Thus, the accelerated B cell maturation observed among farmers' children may be crucial for the allergy-protective effect of a farming environment.