This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
[{'content': 'Chemotaxis is mediated by- \nSelect and explain. \nA. Histamine, B. Leukotriene B4 and C5a, C. Leukotriene C4 and C3a, D. Bradykinin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Chemotaxis is unidirectional locomotion of leukocytes towards the site of injury, oriented along a chemical gradient. This chemical gradient is created by substances called chemoattractants (chemotactic agents), which may be exogenous (bacterial products) or endogenous (C5a, LTB-4, IL-I, TNF, IL-8). C5a is the most powerful chemo-attractant (chemokine REF: ROBBINS pathology 10th edition', 'role': 'assistant'}]