Prospective studies are needed to validate these findings, elucidate their role in FPIES pathophysiology and establish the diagnostic utility of TGF- in milk-induced FPIES. as compared with the and groups. to casein, rendering TGF- a promising biomarker in identifying children who are likely to experience FPIES reactions to this allergen. Prospective studies are needed to validate these findings, elucidate their role in FPIES pathophysiology and establish the diagnostic utility of TGF- in milk-induced FPIES. as compared with the and groups. Casein-specific-IgA levels in negative controls were comparable to children and significantly higher than in the milk-FPIES group (Table 1, Figure 1). Open Docusate Sodium in a separate window Figure 1 Comparison of casein-specific (cs) IgA among the milk-FPIES, milk-FPIES-resolved, other-food-FPIES and negative control children. *: 0.05 0.01, **: 0.01 0.001, ***: 0.001, ns: non-significant Assessing potential IgA dependence on milk exposure In the group of children with IgE-milk allergy [median casein-specific IgE (interquartile range): 8.4(2.3C21.1) IU/ml, csIgA levels were comparable between baseline measurements (when the children were reactive to milk and thus were completely avoiding milk) and measurements 10 months after they became tolerant to regular milk when milk was being ingested regularly in their diet [median (IQR) csIgA: 195.9(62C344) ng/ml vs 219.4(144.5C394.9) ng/ml respectively, Docusate Sodium and four children with available blood samples. There were neither bioactive nor latent TGF- responses [median (IQR): 0 (0C0) ng/ml, ] in stimulated supernatants Docusate Sodium from children with group (and biologic assays such as basophil histamine release assays (19, 20). inhibitory activity has been shown directly or indirectly in several studies (21C24). Low levels of csIgG4 and csIgA could explain the reactions occurring in FPIES due to impaired neutralization capability of the gut microenvironment. TGF- are a group of cytokines that control many biological processes. TGF- is initially released in precursor form known as a latent form that must be activated in the local microenvironment (e.g. pH changes) to become biologically active. This system is so sensitive that small amounts of latent TGF- activation may generate maximum cellular responses, rendering latent TGF- a type of extracellular sensor responding to specific signals by releasing bioactive TGF- (25). In the TGF- assay used in the current study, latent TGF- does not signal unless it becomes activated. To measure TGF-, we artificially activated it by acid treatment. PBMCs from milk-FPIES children showed deficient TGF- responses upon casein stimulation since not only bioactive but also latent TGF- could not be detected with a very sensitive assay. Signaling via the TGF- receptor is crucial for generation of IgA responses (26). Although based on a small sample, the deficient TGF- responses of casein-stimulated PBMCs from milk-FPIES children found in the current study provide a potential explanation for the decreased serum levels of csIgA in these children. It could be argued that lack of exposure would result in fewer circulating casein-specific T-cells in the PBMC population examined. However, lack of casein-specific precursor cells in the PBMCs examined is unlikely if we consider the results from another study that showed that PBMCs from peanut-allergic children, were able to be stimulated with peanut extract, even after using half of the NFATc PBMCs (approximately one million as opposed to two millions in the current study) (27). These observations render TGF- a potential biomarker for FPIES diagnosis, but of course they need to be further studied in larger cohorts of patients. Our findings provide support for the potential role of TGF- in FPIES pathogenesis suggested also by the.