GENERAL HISTOLOGY

Detailed explanation-1: -Histamine is produced in basophils and mast cells and involved in inflammatory responses. Histamine increases the permeability of the capillaries to white blood cells in the infected tissue. Histamine also plays a role in the stomach to aid the production of gastric acid.

Detailed explanation-2: -PGD2 is another major arachidonic acid product primarily produced in mast cells in allergic diseases, inducing vasodilatation, increased vascular permeability, inflammatory cell migration, and cytokine production97.

Detailed explanation-3: -Histamine is a major secretory product of the mast cell and is recognized for its role in the regulation of vasodilation and bronchoconstriction (115, 116). Histamine also regulates functions of monocytes and macrophages (117, 118), eosinophils (117, 118), T cells (119), neutrophils, and endothelial cells (120, 121).

Detailed explanation-4: -Basophils and mast cells produce a wide variety of cytokines and chemokines that recruit and activate other cells (see Table 23.1). Mast cells generate tumor necrosis factor- (TNF-), IL-6, and IL-1, which is consistent with their sentinel role in innate antimicrobial immunity (Chapter 3).

Detailed explanation-5: -Mast cells and basophils represent the most relevant source of histamine in the immune system. Histamine is stored in cytoplasmic granules along with other amines (e.g., serotonin), proteases, proteoglycans, cytokines/chemokines, and angiogenic factors and rapidly released upon triggering with a variety of stimuli.