This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chemical mediators in plasma: Kinin system, Subject name: Pathology
[{'content': 'A laboratory experiment is performed to evaluate the chemotactic potential of a group of potential mediators. Which of the following substances most likely has the greatest affinity for neutrophils? \nSelect and explain. \nA. C5a, B. Fucosyl transferase, C. P-selectin, D. TNF-a', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Several substances have chemotactic potential for neutrophils. C5a is a prominent example Chemotactic Factors Factor Description Chemotactic For Formylated peptides Bacterial products of Escherichia coli Neutrophils C5a Activated complement component Neutrophils HETE, LTB Leukotrienes Neutrophils Kallikrein Product of factor XIIa - mediated conversion, and other cells Neutrophils PAF AGEPC; from basophils, mast cells, and other cells Eosinophils PDGF From platelets, monocytes - macrophages, smooth muscle cells and endothelial cells Neutrophils and macrophages TGF-b From platelets, neutrophils, macrophages, lymphocytes, and fibroblasts Macrophages and fibroblasts', 'role': 'assistant'}]