Parasitic infections<unk> s are activated in response to infection by pathogenic parasites, such as certain helminths and protozoa, through IgE signaling.<unk>  activation disorders<unk>  activation disorders <unk> AD) are a spectrum of immune disorders that are unrelated to pathogenic infection and involve similar symptoms that arise from secreted<unk>  intermediates, but differ slightly in their pathophysiology, treatment approach, and distinguishing symptoms. The classification of<unk>  activation disorders was laid out in 2010. Allergic disease Allergies are mediated through IgE signaling which triggers<unk>  degranulation. Recently, IgE-independent "pseudo-allergic" reactions are thought to also be mediated via the MRGPRX2 receptor activation of<unk> s (e.g. drugs such as muscle relaxants, opioids, Icatibant and fluoroquinolones). Many forms of cutaneous and mucosal allergy are mediated in large part by<unk> s; 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<unk>  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<unk> s 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 cAMP 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<unk> s leads to vasodilation and, if severe, symptoms of life-threatening shock. Histamine is a vasodilatory substance released during anaphylaxis. Autoimmunity<unk> s 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.<unk> ocytosis and clonal disorders<unk> ocytosis is a rare clonal<unk>  disorder involving the presence of too many<unk> s <unk> ocytes) and CD34+<unk>  precursors. Mutations in c-Kit are associated with<unk> ocytosis. Monoclonal disorders Neoplastic disorders<unk> ocytomas, or<unk>  tumors, can secrete excessive quantities of degranulation products. They are often seen in dogs and cats. Other neoplastic disorders associated with<unk> s include<unk>  sarcoma and<unk>  leukemia.<unk>  activation syndrome<unk>  activation syndrome <unk> AS) is an idiopathic immune disorder that involves recurrent and excessive<unk>  degranulation and which produces symptoms that are similar to other<unk>  activation disorders. The syndrome is diagnosed based upon four sets of criteria involving treatment response, symptoms, a differential diagnosis, and biomarkers of<unk>  degranulation.
Mast cell
T cell
Reactive lymphocyte
Dendritic cell
Natural killer cell
Prolymphocyte
Nonspecific immune cell
Basophil