The influence of processing factors and non-atopy-related maternal and neonate characteristics on yield and cytokine responses of cord blood mononuclear cells

Summary Rationale Several studies have evaluated the associations between cord blood cellular responses and atopic diseases in children, but the results of these studies are inconsistent. Variations in blood processing factors and maternal and infant characteristics are typically not accounted for and may contribute to these inconsistencies. Methods Cord blood samples were obtained from 287 subjects participating in the Childhood Origins of ASThma project, a prospective study of children at high risk for the development of asthma/allergies. Mononuclear cells were stimulated with phytohaemagglutinin (PHA), phorbal myristate acetate/ionomycin or a suspension of killed staphylococcus, and IFN‐γ, IL‐10 and IL‐13 were quantitated by ELISA. Cell yields and cytokine production were related to processing factors and maternal and infant characteristics. Results The strongest relationships between independent variables and cell yield or cytokine responses occurred with the season of birth. The highest median cell yields were seen in fall, and the lowest in summer (difference of 47%, P=0.0027). Furthermore, PHA‐induced IL‐5 and IL‐13 responses were approximately 50% higher in spring and summer than in fall or winter (P