Final answer:
Chemokines are small chemoattractant molecules made by epithelial cells, tissue macrophages, and endothelial cells in response to infection or injury. They recruit both monocytes and neutrophils from the blood.
Step-by-step explanation:
Chemokines are small chemoattractant molecules that are made by epithelial cells, tissue macrophages, and endothelial cells in response to infection or injury. They differ slightly in sequence and structure based on the cells that secrete them, but all of them act to recruit both monocytes and neutrophils from the blood.