When do IgE Food Allergies Start?

 

Many believe that the first exposure and subsequent sensitization to foods occurs in maternal milk or formula ingested by the infant after birth.  However, research has shown that this may transpire in the uterus during pregnancy.  In fact, allergen-induced responses have been detected as early as 22 weeks of gestation [1]. 

 

Allergen Proteins in Amniotic Fluid

 

To dive further into this topic, one lab collected amniotic fluid from 20 women, 8 after delivery and 12 during amniocentesis between weeks 15-20 of gestation.  Researchers were able to detect stable food allergens in all 20 samples, with overall concentrations being higher in the amniocentesis group.  These food allergen proteins included dairy, wheat, egg, and more [2]. 

Allergen proteins can enter amniotic fluid when allergens from the mother’s diet pass from her bloodstream through the placenta and into the amniotic fluid.  Amniotic fluid is continuously cycled through the fetal respiratory and gastrointestinal tract until birth [3].    

 

IgE in Amniotic Fluid

 

Immunoglobulin E (IgE) is an antibody which is vital for immunity against parasites as well as in response to various allergic diseases.  The immune system makes IgE antibodies which react to a certain food or foods.  IgE mediated allergic reactions can involve the lungs, eyes, mouth, intestines, brain, heart, or skin and range from mild to life-threatening.  The most common allergens in infants are milk, soy, eggs, peanuts, tree nuts, and wheat. 

 

In another study, researchers collected amniotic fluid and maternal blood from 23 women at 16 weeks and then later at term.  Interestingly, all the analyzed samples contained detectable levels of IgE at both timepoints which correlated with the amount found in the maternal blood samples [4].  Scientists predict that the IgE in amniotic fluid comes predominately from the mother’s blood stream and directly crosses fetal membranes.  It is believed that this mechanism was developed over time to protect the fetus from parasites ingested by the mother during pregnancy.  Additionally, the fetus can begin synthesizing its own IgE as early as 11 weeks of gestation [5]. 

 

Putting it together

 

 

Studies such as these have bridged a gap in describing how infants are born with food sensitivities.  While the fetus is inhaling and ingesting the amniotic fluid, it is taking in allergen proteins as well as IgE antibodies.  This could allow for IgE “focusing” to occur, which essentially means that the antibodies are forming a response mechanism against certain proteins. 

 

This is supported by many follow-up articles.  In 2010, the Sampson lab discovered that maternal consumption of peanuts during pregnancy was significantly associated with peanut allergies in the infant after birth [6].  This has since been reinforced by additional research on the topic.    

 

Takeaways

 

The existence of both allergen proteins and IgE antibodies in amniotic fluid may shed a light on how children are born with food sensitivities before they are orally exposed to any outside substances.  Of course, there are millions of people born each day without any food sensitivities which leads to the question of why this occurs for some fetuses and not others.  More research is needed to establish exactly how and when IgE focusing occurs in amniotic fluid.  Once that is determined, scientists can concentrate on therapeutic targets which could block this response from happening.

 

References

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1. Jones AC, Miles EA, Warner JO, Colwell BM, Bryant TN, Warner JA. Fetal peripheral blood mononuclear cell proliferative responses to mitogenic and allergenic stimuli during gestation. Pediatric Allergy and Immunology. 1996 Aug;7(3):109-16. 

2. Pastor‐Vargas C, Maroto AS, Díaz‐Perales A, Villalba M, Esteban V, Ruiz‐Ramos M, de Alba MR, Vivanco F, Cuesta‐Herranz J. Detection of major food allergens in amniotic fluid: initial allergenic encounter during pregnancy. Pediatric Allergy and Immunology. 2016 Nov;27(7):716-20.

3. Pitkin RM, Reynolds WA. Fetal ingestion and metabolism of amniotic fluid protein. American journal of obstetrics and gynecology. 1975 Oct 15;123(4):356-63.

4. Jones CA, Warner JA, Warner JO. Fetal swallowing of IgE. The Lancet. 1998 Jun 20;351(9119):1859.

5. Miller DL, Hirvonen T, Gitlin D. Synthesis of IgE by the human conceptus. Journal of Allergy and Clinical Immunology. 1973 Sep 1;52(3):182-8.

6. Sicherer SH, Wood RA, Stablein D, Lindblad R, Burks AW, Liu AH, Jones SM, Fleischer DM, Leung DY, Sampson HA. Maternal consumption of peanut during pregnancy is associated with peanut sensitization in atopic infants. Journal of Allergy and Clinical Immunology. 2010 Dec 1;126(6):1191-7.