[ English | Japanese ]Since the late 1980s, immediate-type allergic reactions provoked by natural rubber products have been reported around the world. These reactions are now known as "latex allergy" because such products are made from latex, which is a milky fluid oozing from the tapped trunk of a rubber tree. The causative goods are wide-ranging, from medical devices and dental materials to household products. Latex allergy is prevalent in people who repeatedly come into contact with natural rubber products. For instance, several surveys have revealed that approximately 5-15 % of doctors and nurses who inevitably use natural rubber products in their daily operations have IgE antibodies to antigens originating in the latex. Latex antigens are especially abundant in extracts of dipped rubber products, but are also detected in the donning powder applied to the surface of latex gloves and abraded automobile-tire dust. Inhalation of these airborne allergens can newly sensitize people and can provoke asthma in already sensitized people. The clinical manifestation of latex allergy is relatively mild in most cases, like a local rash, but it sometimes develops to generalized urticaria and even anaphylaxis. Some fatal cases have been reported in the United States. Scientific investigations of the allergens responsible for this immediate-type hypersensitivity have been carried out in many countries. It is now known, as mentioned above, that proteins coming from the latex and their derivatives persistent to the final products are the cause of latex allergy. However, the detailed properties and physiological roles of each allergenic protein remain to be scrutinized .
One of the remarkable features of latex allergy is the patients' extensive cross-reactivity to various kinds of plant-derived foods such as fruits, vegetables, and legumes . This phenomenon is referred to as "latex-fruit syndrome". Some latex-allergic patients also have a hypersensitivity to some kinds of pollen and medical plants. Manifestation of the latex-fruit syndrome is comparable to that of "pollen-food allergy syndrome," where patients suffering from pollinosis also experience food allergies ranging from itching and pruritus around the oral cavity ("oral allergy syndrome": OAS) to generalized urticaria and even anaphylaxis. Extensive cross-reactivity of an allergic patient is usually observed when a plant protein or a protein family conserved in the course of evolution provides common epitopes for IgE antibodies. However, the taxonomic dissimilarity among the causative plants for the latex-fruit syndrome has kept us from any concrete explanation of the cross-reactive antigens.
In the Division of Medical Devices, National Institute of Health Sciences, Japan, we are pursuing a study of latex allergens. A detailed knowledge of latex allergens is indispensable to developing safety tests of natural rubber products and a reliable diagnosis of sensitized people. At the launch of our research, we paid strict attention to the cross-reactivity of latex-allergic people. Intriguingly, it is well known that a series of protective plant proteins induced under stressful conditions have structural and serologic similarities, irrespective of the original spices. Rubber trees cultured in plantations seem to express a large number of such proteins because they are repeatedly tapped and treated with a plant hormone for more efficient latex
production. We have therefore hypothesized that the defense-related proteins of the plants are the latex allergens and the cross-reactive antigens relevant to latex-fruit syndrome (Figure). Through the verification of this hypothesis, we have identified several latex antigens recognized by the IgE antibodies of latex-allergic patients and exemplified the pertinence of defense-related proteins to the extensive cross-reactivity [3-16]. Latex allergy is recognized as a preventable disorder if proper action is taken, including the elimination of powdered latex gloves from medical settings. One important route to sensitization and symptom elicitation for latex-allergic patients is indeed inhalation of airborne
allergens. We believe it urgent to provide accurate information regarding latex allergy to susceptible populations so as to not increase the number of latex-sensitized people in the future.
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