Abstract
Food allergy is a common health problem in childhood since its prevalence was estimated to range from 6. 5 to 24.6% in European countries. Recently, a lot of research has focused on the impact of breastfeeding on oral tolerance induction. Since it was found that breast milk contains immunologically active food antigens, it would be very helpful to clarify the factors of antigen shedding that promotes oral tolerance. This narrative review aimed to summarize the latest evidence from experimental and human studies regarding allergen characteristics in human milk that may influence oral tolerance induction. A literature search in PubMed, MEDLINE, and Google Scholar was conducted. The diet of the mother was found to have a direct impact on allergen amount in the breastmilk, while antigens had different kinetics in human milk between women and depending on the antigen. The mode of antigen consumption, such as the cooking of an antigen, may also affect the allergenicity of the antigen in human milk. The dose of the antigen in human milk is in the range of nanograms per milliliter; however, it was found to have a tolerogenic effect. Furthermore, the presence of antigen-specific immunoglobulins, forming immune complexes with antigens, was found more tolerogenic compared to free allergens in experimental studies, and this is related to the immune status of the mother. While examining available data, this review highlights gaps in knowledge regarding allergen characteristics that may influence oral tolerance.
Highlights
Food allergy is an adverse immune response to otherwise harmless food allergens that results in clinical symptoms and even in life-threatening anaphylaxis
The major peanut allergen Ara h6 was rapidly detected in breast milk, as soon as 10–20 min after ingestion, when ingestion was on an empty stomach, indicating that consuming peanut with other food delayed the secretion of peanut proteins in human milk [12]
Experimental studies showed that maternal immune status to an antigen plays a role in oral tolerance induction in the offspring [36]
Summary
Food allergy is an adverse immune response to otherwise harmless food allergens that results in clinical symptoms and even in life-threatening anaphylaxis. It was found that the diet of the mothers affected the antigen concentrations in breast milk if they had detectable levels of food antigens in their breast milk This was proven for different food antigens, such as OVA [13, 15, 16], beta-lactoglobulin (BLG) [19, 20], and peanut allergens [17, 18]. The major peanut allergen Ara h6 was rapidly detected in breast milk, as soon as 10–20 min after ingestion, when ingestion was on an empty stomach, indicating that consuming peanut with other food delayed the secretion of peanut proteins in human milk [12]. Some allergens (peanuts) had a rapid shedding and clearance, while some others (e.g., BLG) had a more long-lasting shedding, and even some others (e.g., OVA) had a shedding of interim duration These discrepancies could be attributed to the different study protocols. There is a need for more studies to assess the peak levels and the duration of shedding of different antigens in women and to assess the impact of slow or rapid shedding in oral tolerance induction
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