1, 2, 3

A new review [Allergy (2009) vol. 64 (3) pp. 348-353] examines the evidence that

(1) failure to up-regulate the interferon gamma (IFNg) response during infancy is an important determinant of the risk of allergic disease
(2) expression of the IFNg gene in naive T-cells is regulated by epigenetic mechanisms, and
(3) failure to up-regulate IFNg gene expression of naive T-cells associated with low early life microbial exposure.

If we replace “microbial exposure” with “vitamin D supplementation” this sounds like a reasonable model according to more papers that argue

studies combining early life epidemiological data with an investigation of the kinetics of IFNg demethylation in naive T-cells, whilst logistically scientifically challenging, are a promising line of future inquiry.

yea, yea.