Usefulness of Faecal Markers in Cow’s Milk Protein Immunomediated Reactions

Cow’s milk protein allergy (CMPA) affects children most commonly than adults, with symptoms usually developing before 1 year of age and within 1 week after the intake of cow’s milk. Food allergies can be divided into: IgE mediated and non-IgE mediat‐ ed. Some reactions may include both mechanisms (mixed type). The most studied faecal Mar-kers, so far, are calprotectin, Tumor necrosis factor-alpha (TNF-α), beta-defensin and eosinophil cationic protein (ECP). Calprotectin belongs to the S-100 family of calcium-binding proteins and seems to be involved in the regulation of inflammation. Faecal calprotectin (FC) values are significantly higher in infants suspected of having CMPA than in a comparison group of healthy infants. Moreover, there is a significant decrease in FC in infants with CMPA after a period of dietary antigen elimination, although levels use to remain higherthan in age- and diet-matched comparisons. TNF-α is a cytokine involved in systemic inflammation and is one of the cytokines that make up the acute phase reaction. TNF-α expression in the epithelial cells and mononuclear cells in the lamina propria is markedly increased in FPIES patients. TNF-α is also increased in the stools of patients with gastrointestinal milk allergy after milk challenge. Defensins are small (~29 to 42 amino acid) cationic arginine and cysteine rich, amphipathic peptides with a molecular weight of 3–5 kDa. They can be classified into three groups: α-, β- and θ-defensins. Among them, only α- and β-defensins are expressed in humans. Defensins display various functions, including antimicrobial activity and also act as chemoattractant. They contribute to host immunity and to maintain the balance between pathogens and normal flora. Beta-defensins values detected in infants with a previous diagnosis of CMPA prior to the oral food chal‐ lenge, and during each provocation do not seem to show significant changes. ECP is a single-chain, zinc-containing protein with a molecular weightranging from 16 to 22 kDa and is one of the most important proteins in the granules of eosinophil granulocytes. Infants with atopic eczema exhibit a specific faecal protein pattern characterized by an increase in both ECP and TNF-α. The faecal concentration of ECP enhances particularly in patients with immediate-type reactions to the cow’s milk challenge whereas faecal TNF-α enhances in those with delayed-type reactions, confirming the different pathogenesis (IgE mediated and non-IgE mediated) of these two types of reactions.