An Analysis of Potential Associations Between Delivery Mode and Dog-Keeping to Basophil FcER1 and Activation Marker Expression During Infancy

Early-life exposures, including dog-keeping and vaginal delivery, are associated with lower rates of childhood allergy. The underlying immune mechanism(s) are unknown. Basophils are innate immune cells capable of promoting Th2 polarization and allergy development. We explored associations of these exposures with basophil FcεR1 and activation marker expression during the first 6 months of life. Basophil-lineage cells (low side scatter/Class II−/CD123+ from the enriched granulocyte fraction) FcεR1, CD63 and CD203c were identified by flow cytometry in cord blood and at age 6 months in the Microbes, Allergy, Asthma and Pets birth cohort. Concomitant total IgE levels were determined. Dog-keeping during pregnancy and delivery mode data was collected prospectively. Analysis included non-parametric testing using Kruskal-Wallis and Wilcoxon rank sum comparisons. No associations between dog-keeping (any vs. none) and basophil marker expression were apparent. However, children from homes with >1 dog had lower proportions of basophils expressing CD63 at 6 months (median=11.9%, n=18) than those with 0 or 1 dog (median=21.3%, n=33; median=30.7%, n=26, respectively; p=0.045). A trend for lower percentage FcεR1 expression with >1 dog was noted (p=0.096). Vaginal delivery was associated with proportionally fewer basophils expressing FcεR1 versus c-section in cord blood only (median=13.7%, n=80; median=50%, n=16, respectively; p=0.031). Cord and 6 month IgE levels did not correlate with basophil marker expression. Early-life exposure to multiple dogs is associated with lower proportions of basophils expressing CD63 at 6 months. Natural parturition is associated with lower proportions of basophils expressing FcεR1 in cord blood. These associations may relate to lowered allergy risk.