Infectious Disease

Household size linked to allergic sensitization

August 08, 2022

2 min read

Source/Disclosures

Disclosures:
Ponsonby reports receiving fellowship support from the National Health and Medical Research Council. Please see the study for all other authors’ relevant financial disclosures.

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Researchers found an association between larger households and higher naive regulatory T-cell levels, which in turn were associated with less allergic sensitization and disease at age 12 months, according to a study.

There were also associations between multiple prenatal and postnatal microbial factors and the development of naive T regulatory (nTreg) and activated T regulatory (aTreg) cells, the researchers wrote in the study, published in Pediatric Allergy and Immunology.

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Led by Anne-Louise Ponsonby, BMedSci, MBBS, PhD, FAFPHM, FRACP, professor with the Florey Institute of Neuroscience and Mental Health in Parkville, Australia, the researchers said that FoxP3-positive Treg cells help maintain immune tolerance to foods and other environmental allergens.

In response to antigenic immunostimulation, the researchers continued, nTreg cells in circulation can become aTreg cells. Previously, the researchers had reported that deficits of nTreg cells at birth predict food allergy at age 1 year.

The researchers examined data — including 19 prenatal environmental microbial factors — from the Barwon Infant Study of 1,074 infants born to women recruited between June 2010 and June 2013.

Among the 463 infants whose Treg levels were measured at birth via cord blood, those with larger family sizes of three or more residents and one or more siblings had higher proportions of nTreg in their cord blood (P < .0001).

The researchers also found associations between higher nTreg levels and a range of environmental microbial factors at age 6 and 12 months (n = 191). For example, exclusive or mixed breastfeeding vs. no breastfeeding had stronger associations with higher nTreg levels at age 6 months.

The researchers further found little association between environmental microbial factors and aTreg proportions at birth; however, they did find an association between larger household size and higher aTreg levels at age 6 months.

At age 12 months, there were associations between higher aTreg levels and dog ownership and higher maternal and paternal occupational social contact, the researchers found, including evidence of dose-response.

Across the first postnatal year, higher nTreg (P < .001) and aTreg (P = .007) proportions were found among infants from larger households, with higher nTreg proportions found among infants with a pet dog (P = .01).

Further, breastfed infants had higher longitudinal nTreg and aTreg proportions. Those who attended formal childcare had higher longitudinal nTreg (P = .02) but not aTreg proportions in the first postnatal year.

Based on a receiver operating characteristic analysis, the researchers found that infants with 3% or more nTreg at birth were markedly less likely to experience allergic outcomes including food allergy (adjusted OR = 0.21; 95% CI, 0.09-0.5) and atopic eczema ( aOR = 0.26; 95% CI, 0.1-0.64).

Also, the researchers found a strong association between polysensitization at age 1 year and any allergic disease, including food allergy, atopic eczema, and/or atopic asthma, at age 4 years (aOR = 9.26; 95% CI, 2.46-34.85).

Reduced risks for allergic polysensitization, food allergy, atopic eczema and atopic wheeze by age 1 year were associated with higher proportions of cord blood nTreg. Also, larger household size had the most consistent association among the evaluated microbial factors with increased proportion of nTreg in cord blood at birth and with higher proportions of nTreg and aTreg during the first postnatal year.

Overall, the researchers concluded that there was an association between larger household size and higher nTreg proportions at birth and with higher nTreg and aTreg proportions through the first postnatal year.

However, these higher nTreg proportions at birth but not at 6 or 12 months predicted allergic outcomes by age 12 months, indicating that inadequate prenatal immune priming is important in allergic disease development.

Noting several features indicating possible causality, the researchers called for additional research should evaluate the immune priming role of previous pregnancies in the mother as well as the effects of the duration of labor.

Epigenetic studies should be included in studies of the prenatal programming of Treg cells as well, along with the influence of the maternal and infant gut microbiomes on the infant immune profile, the researchers added.

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