to the presence of a not yet defined quorum sensing molecule (basal histamine itself?). those patients are prone to food intolerance driven by another less specific path than the ige receptor path: certainly the mrgprx2 route. these patients also show cyclical skin pathergy and dermographism, every time the bacteria exits its hidden intracellular location. enzymes enzymefunction lyn tyrosine kinasephosphorylates the itams in the fcεr1 β and γ chain in the cytoplasm. it causes syk tyrosine kinase to get recruited to the itams located on the γ chains. this causes activation of the syk tyrosine kinase, causing it to phosphorylate syk tyrosine kinasetargets multiple proteins and causes their activation phospholipase ccatalyzes phosphatidylinositol 4,5-bisphosphate inositol trisphosphateelevates calcium levels diacylglycerolactivates protein kinase c fynphosphorylates gab2 gab2binds to phosphoinositide 3-kinase phosphoinositide 3-kinaseactivates protein kinase c protein kinase cactivates myosin light-chain phosphorylation granule movements that disassemble the actin-myosin complexes rab-associated kinases and phosphatasesregulate cell granule membrane fusion in resting mast cells clinical significance parasitic infections mast cells are activated in response to infection by pathogenic parasites, such as certain helminths and protozoa, through ige signaling. mast cell activation disorders mast cell activation disorders (mcad) are a spectrum of immune disorders that are unrelated to pathogenic infection and involve similar symptoms that arise from secreted mast cell intermediates, but differ slightly in their pathophysiology, treatment approach, and distinguishing symptoms. the classification of mast cell activation disorders was laid out in 2010. allergic disease allergies are mediated through ige signaling which triggers mast cell degranulation. recently, ige-independent "pseudo-allergic" reactions are thought to also be mediated via the mrgprx2 receptor activation of mast cells (e.g. drugs such as muscle relaxants, opioids, icatibant and fluoroquinolones). many forms of cutaneous and mucosal allergy are mediated in large part by mast cells; they play a central role in asthma, eczema, itch (from various causes), allergic rhinitis and allergic conjunctivitis. antihistamine drugs act by blocking histamine action on nerve endings. cromoglicate-based drugs (sodium cromoglicate, nedocromil) block a calcium channel essential for mast cell degranulation, stabilizing the cell and preventing release of histamine and related mediators. leukotriene antagonists (such as montelukast and zafirlukast) block the action of leukotriene mediators and are being used increasingly in allergic diseases. calcium triggers the secretion of histamine from mast cells after previous exposure to sodium fluoride. the secretory process can be divided into a fluoride-activation step and a calcium-induced secretory step. it was observed that the fluoride-activation step is accompanied by an elevation of cyclic adenosine monophosphate (camp) levels within the cells. the attained high levels of camp persist during histamine release. it was further found that catecholamines do not markedly alter the fluoride-induced histamine release. it was also confirmed that the second, but not the first, step in sodium fluoride-induced histamine secretion is inhibited by theophylline. vasodilation and increased permeability of capillaries are a result of both h1 and h2 receptor types. stimulation of histamine activates a histamine (h2)-sensitive adenylate cyclase of oxyntic cells, and there is a rapid increase in cellular that is involved in activation of h+ transport and other associated changes of oxyntic cells. anaphylaxis in anaphylaxis (a severe systemic reaction to allergens, such as nuts, bee stings, or drugs), the body-wide degranulation of mast cells leads to vasodilation and, if severe, symptoms of life-threatening shock. histamine is a vasodilatory substance released during anaphylaxis. autoimmunity mast cells may be implicated in the pathology associated with autoimmune, inflammatory disorders of the joints. they have been shown to be involved in the recruitment of inflammatory cells to the joints (e.g., rheumatoid arthritis) and skin (e.g., bullous pemphigoid), and this activity is dependent on antibodies and complement components. mastocytosis and clonal disorders mastocytosis is a rare clonal mast cell disorder involving the presence of too many mast cells (mastocytes) and cd34+ mast cell precursors. mutations in c-kit are associated with mastocytosis. neoplastic disorders mastocytomas, or mast cell tumors, can secrete excessive quantities of degranulation products. they are often seen in dogs and cats. other neoplastic disorders associated with mast cells include mast cell sarcoma and mast cell leukemia. mast cell activation syndrome mast cell activation syndrome (mcas) is an idiopathic immune disorder that involves recurrent and excessive mast cell degranulation and which produces symptoms that are similar to other mast cell activation disorders. the syndrome is diagnosed based upon four sets of criteria involving treatment response, symptoms, a differential diagnosis, and biomarkers of mast cell degranulation. history mast cells were first described by paul ehrlich in his 1878 doctoral thesis on the basis of their unique staining characteristics and large granules. these granules also led him to the incorrect belief that they existed to nourish the surrounding tissue, so he named them mastzellen (from german mast 'fattening', as of animals). they are now considered to be part of the immune system. research autism research into an immunological contribution to autism suggests that autism spectrum disorder (asd) children may present with "allergic-like" problems in the absence of elevated serum ige and chronic urticaria, suggesting non-allergic mast cell activation in response to environmental and stress triggers. this mast cell activation could contribute to brain inflammation and neurodevelopmental problems. histological staining toluidine blue: one of the most common stains for acid mucopolysaccharides and glycoaminoglycans, components of mast cells granules. bismarck brown: stains mast cell granules brown. surface markers: cell surface markers of mast cells were discussed in detail by heneberg, claiming that mast cells may be inadvertently included in the stem or progenitor cell isolates, since part of them is positive for the cd34 antigen. the classical mast cell markers include the high-affinity ige receptor, cd117 (c-kit), and cd203c (for most of the mast cell populations). expression of some molecules may change in course of the mast cell activation. other organisms mast cells and enterochromaffin cells are the source of most serotonin in the stomach in rodents.