<prompt> A scientist working in the laboratory on the mechanisms involved in inflammation. He observes that the leucocytes leave the blood vessels and move towards the site of bacteria. Which of the following is likely to mediate this movement of the bacteria?C3aC5aHistamineC3b  <response>: After exiting the circulation, leukocytes move in the tissues toward the site of injury by a process called chemotaxis, which is defined as locomotion along a chemical gradient. Both exogenous and endogenous substances can act as chemoattractants, including the following:Bacterial products, particularly peptides with N- formylmethionine termini.Cytokines, especially those of the chemokine family.Components of the complement system, particularly C5a.Products of the lipoxygenase pathway of arachidonic acid AA metabolism, particularly leukotriene B4 LTB 4.Reference-Robbins BASIC PATHOLOGY 10th edition pg-65 