Milk-specific immunoglobulin free light chain secretion is increased in children with eosinophilic esophagitis

Introduction: Eosinophilic esophagitis (EoE) is an esophageal inflammatory disease triggered by foods, milk being the most common by far. Standard allergy tests to milk are not predictive. Immunoglobulin free light chains (IgfLC) were shown to be elevated in allergic diseases in an antigen-dependent manner and independently from serum IgE levels. We sought to investigate whether milk-specific IgfLC secretion is increased in children with EoE. Methods: Serum samples from 40 children with EoE, 11 gastroesophageal reflux disease (GERD) and 11 controls were retrieved. Age and atopic status were recorded. Serum milk-IgfLC levels were determined by ELISA where milk protein concentrate was coated to a plate. Binding of milk-IgfLC was detected by kappa (K) or lambda (L) IgfLC-specific antibodies. Optical density (OD) values for K and L milk-IgfLC were compared among the 3 groups. Serum milk-IgE levels were measured in all subjects by fluoro-enzyme immunoassay. P <0.05 was considered significant. Results: Serum milk-IgfLC levels were significantly more elevated in EoE than in GERD or controls. For K: median OD 0.32 in EoE vs 0.17 in GERD (P = 0.01) and 0.18 in controls (P = 0.01). For L: median OD 0.26 in EoE vs 0.24 in GERD (P = 0.01) and 0.20 in controls (P = 0.005). OD values were comparable between GERD and controls. Serum milk-IgfLC levels did not correlate with age (K: R = 0.20, P = NS; L: R = 0.23, P = NS), serum milk-IgE (K: R = 0.23, P = NS; L: R = 0.21, P = NS), or atopic status (K: median OD 0.25 in atopic vs 0.30 in non-atopic, P = NS; L: median OD 0.25 in atopic vs 0.26 in non-atopic, P = NS). Conclusion: Milk-specific IgfLC secretion is increased in children with EoE, milk being the most common food trigger. This increase was independent of age, milk sensitisation status or atopic status. These results indicate that IgfLC may be important in the pathogenesis of food-induced EoE, and may potentially pave the way to development of a diagnostic test for food triggers in EoE.