Figure 1. Microbial exposure in the first week of life is central for expression of several immune signaling- and response-related genes in the mucosal environment. Relative quantification (RQ) of gene expression of immune-regulating receptors (TLR2, TLR4) and cytokines (IL-10, TGF-β, TSLP, IFN-γ), the chemokine CXCL16 and the defensin Reg3γ were measured by quantitative real time PCR (qPCR) in ileal tissues of specific pathogen-free (SPF), germ-free (GF) and ex-GF mice colonized by co-housing with SPF mice at one (1W) or three weeks (3W) of age. TaqMan assays were used for qPCR, and fold change was calculated as 2-ΔΔCT where ΔΔCT = ΔCT(sample) - ΔCT(calibrator), where the average ΔCT of samples from SPF mice was used as calibrator. The mean is depicted. ***p < 0.001, **p < 0.01, *p < 0.05, compared with the SPF group.