IgE-mediated shellfish allergy constitutes an important cause of food-related adverse reactions. Shellfish are classified into mollusks and crustaceans, the latter belonging to the class of arthropoda. Among crustaceans, shrimps are the most predominant cause of allergic reactions and thus more extensively studied. Several major and minor allergens have been identified and cloned. Among them, invertebrate tropomyosin, arginine kinase, myosin light chain, sarcoplasmic calciumbinding protein, and hemocyanin are the most relevant. This review summarizes our current knowledge about these allergens.IgE-mediated shellfish allergy constitutes an important and increasing health issue in both children and adults (1, 2). During the last two decades, significant progress in biochemistry and molecular biology enabled the characterization, cloning, and recombinant production of various shellfish allergen components and epitope-emulating peptides that might become available for quantification of specific IgE (sIgE) antibodies, namely molecular diagnosis. This review intends to summarize our current knowledge about shellfish allergens and their cross-reactivity as this might be the key to optimize diagnosis (3, 4). Table 1 summarizes the most relevant shellfish allergens that have currently been characterized. Tropomyosin is considered to be the major allergen in shellfish allergy. Actually, already in the early 1980s Hoffman et al. (5) identified a heat-stable IgE-binding allergen in shrimps that was later identified as tropomyosin in brown shrimp (Penaeus aztecus) reacting with 28/ 34 (82%) of shrimp-sensitive individuals (6). Moreover, tropomyosin has been identified as a panallergen of many invertebrate species including other crustaceans (lobster, crab), mollusks (mussels, oysters, scallops, octopus, squids, snails, abalones, whelk, clams, razor shell), cockroaches, and mites (7-18). Tropomyosins are present in both muscle and nonmuscle cells. In striated muscle, they mediate the interaction of troponin-actin complex to regulate contraction. Note that tropomyosins from crustaceans share a high homology (up to 98%), whereas the amino acid sequence identity between (3,(19)(20)(21)(22)(23)(24)(25). Children were once reported to recognize a greater epitope repertoire than adults and thus suggested that shrimp sensitization could decrease over age (22). However, more recent studies with challenged patients could not reproduce this observation with the same epitope mapping (3, 24). About one decade ago, a recombinant tropomyosin from Penaeus aztecus, rPen a 1, became commercially available for molecular diagnostic testing, with improved results as a diagnostic tool in comparison with the whole-shrimp extract (26,27). In addition to tropomyosin, several other allergenic components have been identified in shellfish. In 2003, Yu et al. identified a novel allergen in Penaeus monodon (black tiger shrimp) (28), designated as Pen m 2, with arginine kinase activity. Similar to tropomyosin, arginine kinase is highly abundant i...
