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BACKGROUND: Cow's milk is one of the most common causes of food allergy. In two-thirds of patients, adverse symptoms following milk ingestion are caused by IgE-mediated allergic reactions, whereas for one-third, the mechanisms are unknown. Aim of this study was to investigate whether patients suffering from non-IgE-mediated cow's milk protein intolerance can be distinguished from persons without cow's milk protein intolerance based on serological measurement of IgG and IgA specific for purified cow's milk antigens. METHODS: We determined IgG(1-4) subclass and IgA antibody levels to purified recombinant ?S1-casein, ?S2-casein, ?-casein, ?-casein, ?-lactalbumin, and ?-lactoglobulin in four patient groups by ELISA: Patients with IgE-mediated cow's milk allergy (CMA, n=25), patients with non-IgE-mediated cow's milk protein intolerance (CMPI, n=19), patients with gastrointestinal symptoms not associated with cow's milk ingestion (GI, n=15) and control persons without gastrointestinal problems (C, n=26). Cow's milk-specific IgE levels were determined by ImmunoCAP. RESULTS: Only CMA patients had IgE antibodies to cow's milk. Cow's milk allergic patients mounted the highest IgG(1) and IgG(4) antibody levels to ?S1-casein, ?S2-casein, ?-casein, ?-casein, and ?-lactalbumin. No elevated levels of IgG(4) , IgA, and complement-binding IgG subclasses (IgG(1) , IgG(2) , IgG(3) ) to purified cow's milk allergens were found within the CMPI patients compared to persons without cow's milk protein intolerance (GI and C groups). CONCLUSION: Cow's milk protein intolerant patients cannot be distinguished from persons without cow's milk protein intolerance on the basis of IgG subclass or IgA reactivity to cow's milk allergens.

SummaryBackground Cow’s milk is one of the most common causes of food allergy affectingapproximately 2.5% of infants in the first years of their life. However, only limitedinformation regarding the allergenic activity of individual cow’s milk allergens is available.ObjectiveToanalysethefrequencyofIgEreactivityandtodeterminetheallergenicactivityofindividual cow’s milk allergens.MethodsA nitrocellulose-based microarray, based on purified natural and recombinant cow’smilk allergens was used to determine IgE reactivity profiles using sera from 78 cow’s milk-sensitized individuals of varying ages. The allergenic activity of the individual allergens wastested using patients’ sera for loading rat basophil leukaemia cells (RBL) expressing thea-chain of the human receptor FceRI.Results Using the microarray and the RBL assay, cow’s milk allergens were assessed forfrequency of IgE recognition and allergenic activity. Moreover, the RBL assay alloweddistinguishing individuals without or with mild clinical reactions from those with severesystemic or gastrointestinal symptoms as well as persons who grew out cow’s milk allergyfrom those who did not.Conclusions Component-resolved testing using milk allergen microarrays and RBL assaysseems to provide useful additional diagnostic information and may represent a basis forfuture forms of prophylactic and therapeutic strategies for cow’s milk allergy.Keywords Basophil degranulation, cow’s milk allergy, diagnosis, microarray, recombinantallergenSubmitted 15 March 2010; revised 8 June 2010; accepted 13 July 2010