Radio-resistant CFs produce GM-CSF after CAWS challenge. (a and b) Reciprocal B6.Ly5.1 (WT) and GM-CSF^−/− (GM^−/−) BM chimeras were challenged with CAWS, and 1 d later, the hearts were analyzed for cardiac vasculitis. (a) Dot plots are gated on heart-resident (in vivo Gr-1⁻) myeloid cells (CD11b⁺). (b) Graphs depict the mean ± SEM number of neutrophils (neuts.) and monocytes (mono.) and ICAM/VCAM expression on cardiac endothelium (endo.; data are pooled from four to nine mice from four experiments). (c and d) Hearts from naive or CAWS-challenged mice (6 h after injection) were sorted into CD45⁺ leukocytes (leuko.), CD45⁻CD31⁺ endothelial cells, CD45⁻gp38⁺ CFs, and CD45⁻CD31⁻gp38⁻ stromal cells (stroma), and the expression of cytokines and chemokines was analyzed by qPCR. (d) Bar graphs show mean ± SEM gene expression relative (rel.) to Gapdh pooled from three experiments. fibro., fibroblasts; FSC, forward side scatter. (e) Fibroblasts (CD45⁻CD31⁻gp38⁺) were sorted from the heart, lung, and LN of naive and CAWS (∼10 h after challenge) mice, and GM-CSF expression was measured by qPCR. Expression is normalized to naive tissue fibroblasts and shows the mean ± SEM from two experiments (n = 5–6 mice). (f) The expression of GM-CSF by CFs sorted from naive, day 1, or day 28 CAWS-challenged mice was measured by qPCR. Data points show individual experiments (n = 2–3 mice per experiment), with the mean ± SEM indicated. (g) The expression of ICAM and VCAM on CFs was analyzed at various stages after CAWS challenge. FACS plots are gated on CFs (CD45⁻CD31⁻gp38⁺), and graphs depict the mean ± SEM of four to six mice pooled from two experiments. Statistical analysis was performed with unpaired, two-tailed Student’s t tests. *, P < 0.05; ***, P < 0.001.