CCL4 and neoplasm: Leukocytes could cross the blood-brain barrier during the development of tumor.[18] The migration of basophils to the TME has also been demonstrated in primary human tumors.[19,20] It is reported that basophils in tumors can enhance the recruitment of tumor-specific CD8+ T cells to tumors by producing chemokines CCL3 and CCl4.[21] As a rare peripheral leukocyte, the role of basophils has been neglected in previous research.