Lung parenchymal cells, not recruited hematopoietic cells, are essential to ATF3 regulation of chemokine production. (A) BM transplantation schema. CD45.1⁺ WT mice were lethally irradiated and reconstituted with BM from CD45.2⁺ WT (white) or ATF3^−/− (black) mice. Ten to 12 weeks after transplant, CD45.1⁺ WT mice with CD45.2⁺ WT (white) or ATF3^−/− (gray) BM were used for experimentation. (B) LPS challenge (i.t.) and BAL fluid determination of (left) CXCL1 or (right) CXCL2 by ELISA at 4 hours in CD45.1⁺ WT mice reconstituted with CD45.2⁺ congenic WT (white bars) or ATF3^−/− (black bars) BM cells. Pooled from 3 independent experiments; N = 19 to 20 ATF3^−/− donor conditions and 14 to 15 WT donor conditions. Statistics are unpaired 2-tailed Student t test. (C) MTECs from WT (white bars) or ATF3^−/− (black bars) mice were challenged apically with 10 ng/mL LPS for 18 hours. Basolateral media were then analyzed for (left) CXCL1 or (right) CXCL2 production by ELISA. Representative of 3 experiments; N = 2 to 3 wells/condition. Statistics are 2-way ANOVA with Bonferroni correction. Data are mean ± SEM. ***P < .001.