Fig. 2. Pregnancy modifies the association between PM2.5 and four cytokines (IL-1RA, IL-8, IL-18, and MIF) and significantly affects 12 of 80 cytokines.
(A) Volcano plots summarize the beta (β) coefficients and −log transformed adjusted P values from multivariable linear regression adjusted for potential confounding such as age, ethnicity, asthma status, zip code–level SDI, and batch effect (see Materials and Methods for details). Multiple testing corrections were performed by using FDR ≥ 0.05. Significant cytokines were labeled red. A negative β coefficient of interaction between pregnant and PM2.5 status can be interpreted as the relationship between PM2,5 and cytokines getting weaker in pregnant women compared to nonpregnant women. β greater than 0 indicates a positive association. For PM2.5, it means that for every 1-unit (μg/m3) increase in PM2.5, the expression of markers will increase by the β coefficient value. For pregnant status, the expression of markers will increase by the beta coefficient value among pregnant women compared to nonpregnant women. (B) Scatter plots of PM2.5 concentration versus the levels for IL-1RA, IL-8/CXCL8, IL-18, and MIF, which had a significant interaction effect. Points and lines on the scatter plot are colored by pregnant status (pregnant women in red and nonpregnant women in blue). Lines shown are fitted within the pregnant status. FDR-adjusted P values (Q value) of the statistical interaction term between pregnant status and PM2.5 levels are noted below the cytokine name.