This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'A10-year-old male child complains of pain and swelling in the left foot. He gives a history of injury while playing. Migration of leukocytes to the site of injury is mediated by \nSelect and explain. \nA. Cytokines, B. Histamine, C. Chemokines, D. Prostaglandins', 'role': 'user'}, {'content': 'Answer: C \nExplanation: LEUKOCYTE RECRUITMENT\n• The journey of leukocytes from the vessel lumen to the tissue is a multistep process that is\xa0mediated and controlled by adhesion molecules and cytokines called chemokines\nLEUKOCYTE ADHESION\n• Extravasation is the sequence of events in the journey of leukocytes from vessel lumen to\xa0interstitial tissue which include the following steps\n> Margination - leukocytes assume a peripheral portion of lumen along endothelial surface\n> Rolling - leukocytes adhere transiently, detach and bind again and finally adhere firmly\n> Rolling is mediated by Selectins (P, L and E-selectins)\n> Firm adhesion is mediated by Integrins (LFA-1. MAC-1, VLA-4, α4β7)\n> Pavement - endothelium virtually lined by leukocytes\nLEUKOCYTE MIGRATION\n• Diapedesis or transmigration\n> Leukocyte migration through endothelium\n> Occurs mainly in post capillary venules\n> Adhesion molecules involved - CD31 or PECAM-1 (platelet endothelial cell adhesion\xa0molecule)\nCHEMOTAXIS\n• Leukocyte migration toward the site of injury\n• Locomotion oriented along a chemical gradient\n• Chemo-attractants\n> Exogenous - bacterial products (most common)\n> Endogenous\n■ Cytokines, particularly - IL-8\n■ Complement, particularly - C5a\n■ Arachidonic acid metabolites particularly - LTB4\n• Neutrophils predominate in the inflammatory infiltrate during the first 6 to 24 hours\n• Neutrophils are replaced by monocytes in 24 to 48 hours\n• In Pseudomonas infection - cellular infiltrate is dominated by neutrophils for several days\n• In viral infections, lymphocytes may be the first cells to arrive', 'role': 'assistant'}]