IL-22 mRNA expression in blood samples as a useful biomarker for assessing the adverse health effects of PCBs on allergic children.

To facilitate the assessment of adverse effects of very low concentrations of air pollutants on general populations, we planned to establish a reliable biomarker that is also useful in identifying vulnerable populations. For this purpose we monitored several inflammation markers in blood samples from 2 year old Japanese children (N = 30), and found that those children living close to major highways (<50 m) show higher levels of mRNA expression IL-22 in their blood samples than those living further away (+50 m). This tendency was more pronounced among subjects showing positive IgE against egg and milk. We further examined association between IL-22 mRNA expression and PCB residues and found a number of significant positive correlations between each individual PCB congener and IL-22 expression. To identify the most vulnerable population among those children we selected asthma as a typical allergy-related disease, and could show that there are significant differences in the levels of IL-22 mRNA expression between IgE negative non-asthmatic subject and asthmatic children showing positive IgE reaction toward egg or milk, again. These observations support our main conclusion that IL-22 expression is a sensitive biomarker which is useful in identifying sub-populations of children who are especially vulnerable to air pollution.