Hypersensitivity reactions type I

Atopy A genetic predisposition to develop type I hypersensitivity reactions against common environmental antigens commonly seen in patients with allergic rhinitis, asthma, and atopic dermatitis. 

Type I hypersensitivity reactions (immediate hypersensitivity or anaphylaxis) are immunologic responses to a foreign antigen to which a patient has been previously sensitized. Anaphylactoid reactions are not immunoogically mediated however, symptoms and treatment are similar. 

A severe type I hypersensitivity reaction such as systemic anaphylaxis (eg, from insect envenomation, ingestion of certain foods, or drug hypersensitivity) requires immediate medical intervention. 

Figure 6.31 The basis of type I hypersensitivity reactions. The antigens cross-link with IgE antibodies, which are attached to mast cells.

Three mechanisms are implicated in CUS immunologic (ICU), nonimmunologic (NICU), or uncertain mechanism.20 ICU is a type I hypersensitivity reaction that is IgE mediated and is associated with atopy. NICU is the more common variety of CUS. NICU due to cosmetics is most commonly caused by fragrances (e.g., cinnamic aldehyde) and preservatives (e.g., benzoic acid and sorbic acid).2 Parabens have been documented by passive transfer to cause ICU.21... 

Two cases of cocaine-induced type I hypersensitivity reactions, have been reported (223). 

Aspirin hypersensitivity is also a potential concern and can occur in two ways (1) a respiratory reaction, which is more profitimd in patients with rhinitis, asthma, or nasal polyps, or (2) a typical type I hypersensitivity reaction, including urticaria, wheals, angioedema, itching, rash, bronchospasm, laryngeal edema, hypotension, shock, or syncope. This latter response generally occurs within 1 hour of aspirin ingestion. Such aspirin intolerance may manifest itself in 4% to 19% of patients with asthma and may approach 40% of steroid-dependent asthmatics. 

Type I hypersensitivity reactions usually occur within minutes to hours of exposure to an antigen in sensitized individuals. The immediate allergic response is initiated 5 to 30 minutes after allergen exposure and resolves in 30 to 60 minutes.This may be followed by the late-phase reaction, which is more severe and of greater duration. The late phase develops 4 to 6 hours after the initial response and may last up to 2 days. Neutrophils, eosinophils, macrophages, lymphocytes, basophils, and mast cells are involved in the late-phase inflammatory reaction, resulting in tissue damage. 

It has also been hypothesized that a type I hypersensitivity reaction may be involved in some patients. A definitive pathogenic mechanism for episcleritis has still not been established. 

Cyclophosphamide reportedly caused a type I hypersensitivity reaction in a patient with systemic lupus erythematosus (38). 

Allergic reactions to aminoamide local anesthetics are unusual, but type I hypersensitivity reactions are described, and life-threatening anaphylaxis can rarely occur (SEDA-21, 136) (SEDA-22, 134). Cross-reaction between amides also occurs, for example articaine, bupi-vacaine, lidocaine, and prilocaine (SEDA-22,134). 

Three cases of a type-I hypersensitivity reaction to loxoprofen, characterized by generalized urticarial rash and dyspnea, have been reported (3,4). 

Severe type I hypersensitivity reactions have been reported (SEDA-16, 108). Serious generalized urticaria with angioedema has occurred (2). Rechallenge with oral propyphenazone caused a severe anaphylactic reaction in a patient with a negative skin test. Although the report stressed the importance of oral challenge, it also drew attention to its risks (SEDA-12, 83). 

In contrast, the structurally related etoposide phosphate is highly soluble in aqueous solutions and no solubilizing adjuvants are necessary. Preliminary data suggest that the incidence of hypersensitivity reactions is lower with etoposide phosphate than with etoposide, strengthening the hypothesis that adjuvants have a major role in the development of allergic reactions (123,124). In one case, a patient who had a type I hypersensitivity reaction to etoposide was successfully retreated with etoposide phosphate (134). 

Recent studies characterizing the basis for chemically induced hypersensitivity have uncovered an important interplay between type I hypersensitivity reactions, manifested primarily as respiratory sensitization, and type IV hypersensitivity reactions, manifested primarily as contact sensitization. The most important observation came from studies which showed that a predominantly respiratory sensitizer would still trigger an IgE response when applied topically. This observation can be accounted for by the cytokine network model which was described previously as important for cross talk between humoral immunity and cell-mediated immunity. Basically, a chemical with the capability of being a respiratory sensitizer will trigger an IgE response regardless of its route of exposure because it selects or supports the development of a Tni-dependent response, with the associated cytokine profile, IL-4, IL-5, and IL-10. In contrast, a chemical which lacks the capability of being a respiratory sensitizer but which can still trigger contact dermititis, will select or support a THi-dependent response, with the associated cytokine profile, IL-2 and IFN-y. 

IWeen A buffer used in experimental biology, two-sample test See unpaired t-test. type I hypersensitivity reaction (anaphylactic/immedlate) An unwanted immune response which occurs when antigen evokes IgE production, which then fix to mast cells. Subsequent exposure with antigen results in release of mediators, e.g. histamine, PAF, eicosanoids. from the mast cells. It occurs within minutes or... 

Patients with delayed reactions to penicillin (skin rash) generally can receive cephalosporins. Patients with type I hypersensitivity reactions to penicillins (anaphylaxis) should not receive cephalosporins or carbapenems (alternatives include aztreonam, quinolones, sulfa drugs, or vancomycin based on type of coverage indicated). 

Histamine is an autacoid present at high levels in lungs, skin, and the GI tract and released from mast cells and basophils by type I hypersensitivity reactions, drugs, venoms, and trauma. Histamine receptors are of the serpentine family, with seven transmembrane-spanning domains with G-protein-coupled second messenger effectors. 

Toluenediisocyanate Allergy (type I), hypersensitivity reactions (type II)... 

The production of antibodies known as IgE and a series of interactions between various cell types and chemical mediators are known to be involved in most confirmed cases of food allergy. This type of IgE-mediated allergy or type I hypersensitivity reaction produces immediate symptoms, the most severe form being anaphylaxis. Other immediate symptoms, such as rhinitis, urticaria, and other affections of the mouth, gut, skin, and respiratory tract, may precede anaphylaxis or occur alone as a less severe manifestation. These reactions would be considered as immediate hypersensitivities. Any food that contains protein has the potential to elicit such allergic sensitization. More than 170 different foods have been documented to be responsible for eliciting immediate hypersensitivities (Taylor, 2000). 

In type I hypersensitivity reactions, the penicillin RAST has been used by several authors to estimate the specific IgE response (Assem 1972 Wide and Juhlin 1971). Using a modification of the classical RAST which improves the sensivity of the tests, Adkinson (1975) found an excellent correlation between the positive clinical history, skin tests with PPL, and the results of the RAST. 

IgE Class of antibody that binds to receptors on basophils in the blood or mast cells in the tissues, responsible for allergic or immediate (Type-I) hypersensitivity reactions. 

For many years, two terms, anaphylaxis and anaphylactoid, have been used to describe relatively rare reactions that have features commonly associated with severe immediate, often life-threatening, allergic reactions. These two terms are distinguished by the underlying mechanisms of the reactions. The term anaphylaxis is used by many for an immune IgE antibody-mediated, systemic immediate type I hypersensitivity reaction, often occurring within seconds or minutes. 

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