Abstract
Background: Atopic dermatitis (AD) is a chronic skin condition characterised by the development of pruritic and inflamed lesions. One key component of AD pathogenesis is a cutaneous hyper-reactivity to allergens influenced by a Th2-polarised immune response. Macrophage-derived chemokine (MDC) and Thymus and activation-regulated chemokine (TARC) are two chemokines involved in this pathological immune response. Research has shown a strong association between MDC and TARC levels in blood and AD severity. Recently, some cohort studies have suggested that levels of MDC and TARC in umbilical cord blood (UCB) may be predictive of whether infants will develop AD during childhood. This cohort study aimed to further investigate the potential predictive value of UCB MDC and TARC for AD development in childhood.
Methods: This project involved a retrospective analysis of data obtained from the NZA2CS population birth cohort study. Information about AD-related outcomes was gathered using questionnaires at various time points, along with physical examination of flexural dermatitis and measurement of total and specific IgE levels at age six. UCB MDC levels were measured using enzyme-linked immunosorbent assay (ELISA) techniques for a total of 647 participants. Haemolysis of UCB samples was found to affect TARC measurement; therefore fewer (n = 270) samples were analysed for TARC. Haemolysis of UCB samples did not affect measurement of MDC concentration. Logistic regression was used to calculate odds ratios to determine the association between UCB chemokine levels and development of AD- related outcomes in childhood.
Results: UCB MDC and TARC levels were not predictive of development of AD at age six. Neither were they consistently significantly associated with the development of AD-related outcomes such as an itchy rash or atopy. Some statistically significant associations were found, although their value is difficult to interpret as these were isolated findings. UCB MDC levels were significantly associated with the development of an itchy rash at four years of age (p = 0.027) and with the level of specific IgE to cat allergen at age six (p = 0.05). When the data was segregated by sex, UCB MDC levels in males were consistently significantly associated with development of an itchy rash during childhood (p < 0.05).
Conclusion: UCB MDC and TARC concentrations are unlikely to be clinically useful biomarkers for the development of AD in childhood. This was the largest cohort study so far to investigate cord MDC and TARC levels as predictors of future AD onset, and the findings are concordant one other large cohort study. Therefore, these results do not warrant further research into UCB MDC and TARC as predictive biomarkers of AD development.