Background: Characterizing early abnormalities in immune development of allergic individuals provides an important basis for defining disease pathogenesis and future prevention strategies. This study compares patterns of early immune responses in an established cohort based on allergic outcomes and allergen skin prick test (SPT) reactions at 6 years of age.
Methods: Children from an original birth cohort (n = 60) consisting of 44 high risk (HR) (family history of allergy) and 16 low risk (LR) (no family history) were reassessed at 6 years of age. Detailed clinical information about allergic disease was obtained (n = 53) and a subgroup (n = 31) consented to have allergen SPT to common food and inhalant allergens. Data from previous immunological assessments performed at birth, 1 and 2 years of age, including lymphoproliferation and cytokine [interleukin (IL)-4, IL-5, IL-6, IL-10, IL-13 and interferon (IFN)-gamma] responses to ovalbumin (OVA), house dust mite (HDM), cat allergen (Fel d 1), phytohaemaglutinin (PHA) and tetanus toxoid, were re-analysed based on the 6-year clinical outcomes.
Results: Twenty-eight HR and three LR children had a clinical history of allergic disease at 6 years of age including doctor diagnosed asthma (n = 17) and/or eczema (n = 24). Most children (78%) with atopy at 6 years had positive SPT to the allergens tested, and 70% had symptoms within the last year. Children at genetic risk (family history) of allergy had weaker (P = 0.017) polyclonal T helper 1 (Th1) IFN-gamma responses in the neonatal period compared with LR children. Although children with allergic disease at 6 years also tended to have weaker neonatal IFN-gamma responses compared to those with no symptoms, but this was not quite significant (P = 0.05). A positive SPT to HDM at 6 years was associated with higher IL-13 responses to HDM at 1 year (P = 0.02), whereas allergic disease at 6 years was associated with higher IL-5 messenger RNA (mRNA) responses to HDM at 1 year (P = 0.01). Despite these associations, regression analysis demonstrated that the only significant early predictors of allergic sensitization at 6 years of age were a family history of allergic disease, and atopic symptoms at 2 years. Importantly, none of the early immunological parameters measured were significantly predictive of allergic disease or allergic sensitization in these 6-year-olds.
Conclusions: Although our observations suggest that subtle differential alterations in cytokine responses during early immune development are associated with different aspects of subsequent atopy, there are still no early predictive biomarkers of disease. A positive family history of allergy remains the dominant predictive factor.