<prompt> Histamine in anaphylaxis is secreted byMast cellsB-cellsBasophilsMacrophages  <response>: Ans. a Mast cells. Ref. Robbins pathology, 8th ed., Table 2-4; 2-6.Mediators of anaphylaxis are many--histamine, serotonin, PGS, VIP, Leukotrienes, TxA2, etc., hut histamine is produced and secreted by mast cells.The Actions of the Principal Mediators of InflammationMediatorSourcePrincipal ActionsCell-DerivedHistamineMast cells, basophils, plateletsVasodilation, increased vascular permeability, endothelial activationSerotoninPlateletsVasodilation, increased vascular permeabilityProstaglandinsMast cells, leukocytesVasodilation, pain, feverLeukotrienesMast cells, leukocytesIncreased vascular permeability, chemotaxis, leukocyte adhesion and activationPlatelet-activating factorLeukocytes, endothelial cellsVasodilation, increased vascular permeability, leukocyte adhesion, chemotaxis, degranulation, oxidative burstReactive oxygen speciesLeukocytesKilling of microbes, tissue damageNitric oxideEndothelium, macrophagesVascular smooth muscle relaxation; killing of microbesCytokines e.g. TNF, IL-1Macrophages, lymphocytes, endothelial cells, mast cellsLocal endothelial activation expression of adhesion molecules, systemic acute-phase response; in severe infections, septic shockChemokineLeukocytes, activated macrophagesChemotaxis, leukocyte activationPlasma Protein-DerivedComplementPlasma produced in liverLeukocyte chemotaxis and activation, opsonization, vasodilation mast cell stimulationKininsPlasma produced in liverIncreased vascular permeability, smooth muscle contraction, vasodilation, pain 