Type 1 hypersensitivity

Zhang, S. and Castro, G.A. (1990) Involvement of type 1 hypersensitivity in rapid rejection of Trichinella spiralis from adult rats. International Archives of Allergy and Applied Immunology 93, 272-279. 

Are T Cells Involved in Specific Immune Responses to Autoantigens in Atopic Dermatitis Autoimmune phenomena to human self-proteins may also contribute to the pathophysiology of atopic dermatitis. IgE against autoantigens such as Horn SI-4 have been shown to stimulate type 1 hypersensitivity reactions which in turn may contribute to the clinical cutaneous reactions in atopic dermatitis [15]. Autoallergens induce the proliferation of CLA+ autoreactive T cells derived... 

Cardiovascular effects. Hypotension and tachycardia occur in most patients taking clozapine. Cases of potentially fatal myocarditis and dilated cardiomyopathy have been reported in association with clozapine (Kilian et al. 1999). Myocarditis typically occurred within 3 weeks of starting clozapine, but cardiomyopathy may not be apparent for several years. Although rare, treatment-emergent myocarditis and cardiomyopathy occur at a reportedly higher incidence with clozapine than with other antipsychotics (Coulter et al. 2001). The mechanism by which clozapine may cause myocarditis has not been established, but some authors have speculated that clozapine may cause an immunoglobuhn E (IgE)-mediated type 1 hypersensitivity reaction (Kihan et al. 1999) or a hypereosinophilic syndrome (Hagg et al. 2001). 

Establish the nature of the patient s penicillin allergy and if a history of type 1 hypersensitivity is suspected, suggest an alternative regimen to the clinician to incorporate MRSA cover such as vancomycin plus ciprofloxacin plus metronidazole. Do not delay treatment to allow time for a deep tissue specimen to be taken. 

Q4 Antihistamines are effective in managing many of the troublesome symptoms of allergic rhinitis. Histamine is a neurotransmitter and a mediator of type 1 hypersensitivity reactions, such as urticaria and hay fever. There are several types of histamine receptors and these allergic conditions can be treated with Hi receptor antagonists, such as promethazine, chlorphenamine and fexofenadine. First-generation antihistamines, such as promethazine, cause sedation and possess side effects associated with actions on muscarinic receptors. Fexofenadine is a newer drug with a longer duration of action, which does not sedate the patient. 

Q3 A type 1 hypersensitivity reaction is responsible for the development of the allergy. The symptoms are due to the effects of mast cell degranulation with the release of histamine. Mast cells are located in the nasal passages and the nasal mucosa is sensitive to the effects of histamine released from these cells, leading to inflammation of the mucous membranes of the nose. The inflammation is associated with oedema and swelling, vasodilation and an increase in the secretion of mucus. The mucous membrane of other sections of the respiratory tract (accessory sinuses, nasopharynx, and upper and lower respiratory tract) will also be affected by the allergic reaction. 

Perennial and seasonal allergic rhinitis are type 1 hypersensitivity reactions to an allergen. 

Asthma is an example of a type 1 hypersensitivity (Chapter 15). The incidence of asthma in the United States (as well as in many other developed countries) has reached epidemic proportions. 

Immune-mediated reactions to penicillin G include anaphylaxis (a type 1 hypersensitivity reaction), hemolytic anemia and thrombocytopenia (type II hypersensitivity reactions). Anaphylactic reactions can be fatal, so epinephrine... 

In contrast to viruses and bacteria, helminths are the most active Th2-ceU inducers in both humans and experimental models (Finkehnan et al. 1997 Lawrence 2003). Therefore, worm infections might promote atopy by inducing IL-4 expression, followed by an increased development of allergen-specific Th2 cells. Furthermore, eosinophilia and mastocytosis, which characterize worm infections, may directly increase type 1 hypersensitivity reactions. Helminth infection instead modifies the course of allergic disease (Wohlleben et al. 2004). 

Until more studies are completed and more is known about the mechanism behind reactions to iodine-containing compounds, it is unclear if these responses are true type 1 hypersensitivities. 

Mast Cell Degranulation Mast cells play a role in Type 1 hypersensitivity reactions, but they can also be stimulated by pharmaceuticals in an IgE-independent manner due to direct interactions with mast cell membranes or surface receptors (de Week, 1984). The reaction in vivo typically occurs at maximum drug concentration, or very soon after an IV infusion, and tends to diminish with subsequent exposures to the drug. Pseudoallergy is a rare event, and routine screening... 

Immediate (Type-1) hypersensitivity Response to a foreign substance (allergen) resulting from prior exposure to the allergen. Known also as anaphylactic hypersensitivity. 

Unlike the other types of hypersensitivity caused by antibodies, namely types II and ni, only a proportion of the population, the so-called atopies, have a predisposition to developing a type 1 hypersensitivity reaction when exposed to the allergen in question. Atopy may have a genetic component but type 11 and III reactions like, for example, penicillin-induced hemolytic anemia and serum sickness, may occur in all individuals, and this may result without a prior sensitization phase. 

IgE antibodies to local anesthetics appear to be so rare that some have even doubted that they occur, but occasional case reports indicate an underlying mechanism of type 1 hypersensitivity and some skin test results suggest that these antibodies do exist. Evidence from a dot-blot procedure for an IgE-mediated reaction to lignocaine has been presented, and more recently, IgE antibodies to mepivacaine were reliably detected by a Phadia immunoassay shown by inhibition studies to be specific. 

Immunologic Exposure to latex is associated with three clinical syndromes irritant dermatitis, delayed hypersensitivity reactions, and the most serious, but least common, immediate or type 1 hypersensitivity. Exposure to latex can occur through the skin, mucous membranes, or airways. Gloves used for examination, surgical or household, are often the cause of allergic reactions. 

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