Inflammatory cells in bronchial asthma.
A diagrammatic representation of the interactions between mediators of hypersensitivity and leukocytes in early, late-phase, and ongoing asthma is shown in Figure 1. Early phase or immediate reactions are largely the result of bronchoconstriction consequent to the release of mediators such as histamine, PGD2, LTC4/D4, and PAF. The principal mediator cell (MC) is the mast cell (although other IgE receptor-bearing cells such as the macrophage, eosinophil, and platelet might also be involved in this immediate response). The stimulus for mediator cell activation may be either immunologic (IgE-dependent) or nonimmunologic (i.e., changes in osmolarity as a result of the respiratory water loss associated with exercise-induced asthma). Late-phase reactions appear to be a consequence of infiltration with neutrophils (N), eosinophils (E), and macrophages (M phi). These cells are recruited and activated either by mast cell-associated chemotactic factors [such as LTB4, PAF, the eosinophil chemotactic factor of anaphylaxis (ECF-A), or high-molecular weight neutrophil chemotactic activity (NCA (HMW))] and/or "lymphokines" derived from T-helper cells (TH) which have been stimulated by antigen processed by the antigen-processing cells (APC). These mononuclear cell interactions are under the control of regulatory T cells [T suppressor (TS) cells] and it is speculated that the availability of these subsets may determine the magnitude of the late-phase response. Lymphokines and monokines which selectively activate neutrophils, eosinophils, and monocytes include LIF, EAF, and IFN-gamma, respectively. Macrophage-derived tumor necrosis factor (TNF) also amplifies the inflammatory response by its capacity to enhance eosinophil cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)
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Department of Allergy and Clinical Immunology, National Heart & Lung Institute, London, England.
D001249:Asthma / Q000473:pathology*; D001491:Basophils / Q000502:physiology; D001792:Blood Platelets / Q000502:physiology; D004804:Eosinophils / Q000502:physiology; D006801:Humans; D007249:Inflammation / Q000473:pathology; D008214:Lymphocytes / Q000502:physiology; D008264:Macrophages / Q000502:physiology; D008407:Mast Cells / Q000502:physiology; D009504:Neutrophils / Q000502:physiology