<prompt> 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 byCytokinesHistamineChemokinesProstaglandins  <response>: LEUKOCYTE RECRUITMENT The journey of leukocytes from the vessel lumen to the tissue is a multistep process that is mediated and controlled by adhesion molecules and cytokines called chemokinesLEUKOCYTE ADHESION Extravasation is the sequence of events in the journey of leukocytes from vessel lumen to interstitial tissue which include the following steps Margination - leukocytes assume a peripheral portion of lumen along endothelial surface Rolling - leukocytes adhere transiently, detach and bind again and finally adhere firmly Rolling is mediated by Selectins P, L and E-selectins Firm adhesion is mediated by Integrins LFA-1. MAC-1, VLA-4, α4β7 Pavement - endothelium virtually lined by leukocytesLEUKOCYTE MIGRATION Diapedesis or transmigration Leukocyte migration through endothelium Occurs mainly in post capillary venules Adhesion molecules involved - CD31 or PECAM-1 platelet endothelial cell adhesion moleculeCHEMOTAXIS Leukocyte migration toward the site of injury Locomotion oriented along a chemical gradient Chemo-attractants Exogenous - bacterial products most common Endogenous Cytokines, particularly - IL-8 Complement, particularly - C5a Arachidonic acid metabolites particularly - LTB4 Neutrophils predominate in the inflammatory infiltrate during the first 6 to 24 hours Neutrophils are replaced by monocytes in 24 to 48 hours In Pseudomonas infection - cellular infiltrate is dominated by neutrophils for several days In viral infections, lymphocytes may be the first cells to arrive 