The relationships among shrimp-specific IgG subclass antibodies and immediate adverse reactions to shrimp challenge.

High levels of shrimp-specific IgE, in association with a positive prick test, are not always predictive of a positive, immediate response to double-blind, placebo-controlled, food challenge (DBPCFC) with shrimp. The observation that shrimp-sensitive individuals in general have increased levels of circulating shrimp-specific IgG is of interest because antigen/allergen-specific IgG subclasses have been associated with adverse reactions to foods. Therefore, this current study measured shrimp-specific IgG subclass and IgE antibodies in 31 individuals with histories of immediate, adverse reactions to shrimp immediately before DBPCFC and 20 shrimp-tolerant subjects. Individuals with a history of shrimp sensitivity had significantly raised shrimp-specific IgG2 and IgG4 compared to shrimp-tolerant individuals. Challenge-positive subjects were distinguished from subjects with negative or equivocal responses by an increased IgG2 (p less than or equal to 0.001). Specific IgG4 was not raised (p less than or equal to 0.065). These studies indicate that some shrimp-specific IgG subclass levels are increased in shrimp-sensitive subjects. However, none of the subclass responses were significantly predictive of a positive response to DBPCFC and therefore were not diagnostic of shrimp intolerance.