CCL2 and myelofibrosis: The relative frequency of iFibs was 2-fold higher in myelofibrosis mice than controls (Fig. 3H), and expression of chemokine genes was strongly enriched in the iFibs with significantly increased per cell expression of chemokines in MPL vs. control fibroblasts (Fig. 3I, Table S3), including Kitl, Cxcl12, Ccl2, Cxcl1 (Figs. S3A and S3E).