mature basophil polymorphonuclear leucocyte CALOHA:TS-0688 mature basophil leucocyte BTO:0001026 Mature basophils are also capable of producing IL-3, IL-5, IL-6, IL-8, IL-13, IL-25, CCL22, tslp, vegf, and LTC4. mature basophil leukocyte polymorphonuclear leukocyte A fully differentiated basophil, a granular leukocyte with an irregularly shaped, pale-staining nucleus that is partially constricted into two lobes, and with cytoplasm that contains coarse granules of variable size. Basophils contain vasoactive amines such as histamine and serotonin, which are released on appropriate stimulation. secretory cell basophil