Putative Cord Blood Predictors of Atopy

Abstract

It has been proposed that the in utero environment along with the genetic susceptibility for atopy might influence the risk of allergic disorders in infants. Two key features that are most related with allergic disease are eosinophilia and a heightened T helper cell 2 (Th2) cytokine profile. The differentiation and accumulation of eosinophils and their progenitors are associated with the pathogenesis of these disorders. Eosinophils arise from CD34+ progenitors in the bone marrow and peripheral tissues. Two important molecules related to eosinophilopoiesis are GATA1 and major basic protein (MBP). GATA1 is an essential eosinophil transcription factor and MBP is a cataionic protein found in the granule of mature eosinophils. MBP is coded by the PRG2 gene. The time course of eosinophilopoiesis upon IL-5 stimulation in umbilical cord blood CD34+ progenitor cells from infants with and without risk of atopy has not yet been adequately examined. Additionally, knowledge of the potential differences in cytokine profiles during eosinophilopoiesis between children at high and low atopic risk is lacking. This thesis studied cord blood non-adherent mononuclear cells (NAMNCs) as surrogates of the CD34+ progenitor population in order to examine various predictive biomarkers of future allergic disease. First, differences in gene expression patterns of GATA1 and PRG2 during IL-5 induced eosinophilopoiesis were established. In addition, cell population changes were determined. Specifically, the percentage of CD34+, IL-5Rα+, CD4+ and CCR3+ cells were measured through flow cytometry in NAMNCs following IL-5 stimulation for 72 hours. Finally, cytokine profiles of the NAMNC supernatants were determined. This study found no significant differences in the patterns of gene expression of GATA1 and PRG2 as well as cell population changes in NAMNCs from infants born to atopic versus non atopic mothers. Levels of IL-2,IL-4,IL-6,IL-7,IL-8,IL-10,IL-12,GM-CSF,TNF-α and IFN-γ were significantly up-regulated over time but only the levels of IL-2 and IFN-γ at 48 and 72 hours were significantly different between the atopic and non-atopic samples.

This research describes features of progenitor cell differentiation and cytokine profiles that could be used as putative biomarkers of atopy as early as birth.