he prevalence of immune-mediated diseases such as allergies and autoimmune diseases is on the rise in the developed world. Microbial exposure is known to modulate the risk for these diseases. In order to explore differences in the gene expression patterns induced in utero in infants born in contrasting standards of living and hygiene, we collected umbilical cord blood RNA samples from full-term newborn infants born with normal vaginal delivery in Finland (modern society), Estonia (rapidly developing society) and the Republic of Karelia, Russia (poor economical conditions). Transcriptomic profiles were analyzed using whole genome microarrays including gender, gestational age, birth month and HLA allele genotype as confounding variables in the analysis. The data revealed that the whole blood transcriptome of Finnish and Estonian neonates differ from their Karelian counterparts. Samples from Karelian infants had an increase in transcripts associated with LPS induction and bacterial sepsis observed in 1-year-old infants in earlier studies. The results suggest exposure to toll like receptor (TLR) ligands and a more matured immune response in infants born in Petrozavodsk compared to the Finnish and Estonian infants. These results further support the concept of a conspicuous plasticity in the developing immune system: the environmental factors that play a role in the susceptibility/protection towards immune-mediated diseases begin to shape the neonatal immunity already in utero and direct the maturation of both the adaptive and the innate immune responses in accordance with the surrounding microbial milieu.

Umbilical cord blood was drawn into Tempus Blood RNA tubes (Applied Biosystems) from children born between January and May 2010 at the maternity unit of Jorvi hospital (Espoo, Finland; n=48), maternity units of Tartu and Põlva (Estonia; n=25), or two maternity departments in Petrozavodsk (capital of the Republic of Karelia, Russian Federation; n=40) according to the manufacturer´s protocol and then stored in ?70 °C until analyzed. All newborn infants were full-term (>36 gestational weeks) and born vaginally. 113 cord blood RNA samples were analyzed with Affymetrix U219 gene array. Gender, pregnancy week, month of birth and HLA risk class were included as confounding factors in the analysis model.