RNA-seq analysis of the Treg subpopulation from the murine CLL model revealed its unique phenotype characterized by upregulation of multiple factors, including Il10, Ifnγ, and the chemokines Ccl3/4/5 Cxcl13, which likely contribute to the neutrophil leukemia-supporting phenotype. Here, CCL3 is linked to chronic neutrophilic leukemia.