Eosinophil Production and Function By Jane Liesveld, MD, James P Wilmot Cancer Institute, University of Rochester Medical Center Reviewed / Revised Feb 2022 | Modified Sep 2022 View Patient Education Eosinophils are granulocytes (white blood cells that contain granules in their cytoplasm) derived from the same progenitor cells as monocytes-macrophages, neutrophils, and basophils.