Background: Exposure to environmental microbes in early life might lead to type 1-skewed T cell responses and therefore reduce the risk of allergic diseases.
Objective: To investigate whether the cytokine responses at birth and at age 3 months are associated with environmental factors, especially exposure to microbes. Living in a farm, level of house dust endotoxin, cleanliness of the home, and presence of cats and dogs in the household were studied as possible determinants of cytokine production.
Methods: Twelve farmers' and 17 nonfarmers' children were studied. Production of IL-4, IL-6, TNF-alpha, and IFN-gamma in cord blood and in peripheral blood at 3 months was measured after 8-hour and 24-hour stimulation with phorbol ester plus concanavalin A.
Results: IFN-gamma responses at age 3 months were associated with farming (median, 53 vs 17 pg/mL; P = .019) and cats and dogs (49 vs 14 pg/mL; P = .014) (8 hours). Change in IFN-gamma-producing capacity from birth to 3 months was larger in children with higher than median endotoxin concentration in bed dust (P = .038) and in children with a cat or dog (P = .005) (8 hours). Increased IL-6 responses at birth were associated with cat or dog exposure (P = .004; 8 hours) and endotoxin level in settled dust (P = .039; 24 hours).
Conclusion: The development of IFN-gamma-producing capacity during the first 3 months of life is associated with farming, endotoxin in house dust, and cat and dog exposure. These environmental characteristics may indicate some microbial exposure capable of driving developing immune system toward T(H)1 responses.