• animal exposure;
  • cytokine;
  • dog;
  • immune development;
  • IFN-γ;
  • IL-5;
  • IL-8;
  • IL-10;
  • TNF-α


Background It appears that contacts with furred animals early in life and already during gestation contribute to the immunological development in humans, but the mechanisms and relevant exposures are not clear.

Objective To investigate whether exposure to animals during pregnancy and the first year of life is associated with early immune development, determined as stimulated cytokine responses of children at birth and at age 1 year.

Methods Cord blood (n=228) and peripheral venous blood (n=200) samples 1 year after birth were collected and stimulated with Gram-positive superantigen Staphylococcal enterotoxin B, Gram-negative bacterial lipopolysaccharide (LPS) and the combination of mitogenic phorbol 12-myristate 13-acetate and calcium ionophore ionomycin (P/I) for 24 and 48 h. TNF-α, IFN-γ, IL-5, IL-8 and IL-10 responses were measured by ELISA. For each cytokine, the time-point with the highest response was chosen for further analyses. Animal contacts were surveyed by self-administered questionnaires.

Results Dog ownership was associated with decreased TNF-α-producing capacity at birth (P/I: median 841 vs. 881 pg/106 WBC, P=0.05) and 1 year after birth (P/I: 1290 vs. 1530, P=0.01; LPS: 425 vs. 508, P=0.02). Associations remained significant after adjustment for potential confounders. Cat ownership was not associated with cytokine production.

Conclusion Having a dog in the household in infancy and already during pregnancy may be associated with reduced innate immune responses in early childhood. The observed attenuation of cytokine production may help in preventing exaggerated immune responses against harmless antigens later in life. Thus, intensive exposure to dogs in early life may be beneficial during normal immune maturation.

Cite this as: M. H. J. Lappalainen, K. Huttunen, M. Roponen, S. Remes, M.-R. Hirvonen and J. Pekkanen, Clinical & Experimental Allergy, 2010 (40) 1498–1506.