Exploratory analysis of gene expression profiles. (A) Three-dimensional principal component analysis and (B) unsupervised hierarchical clustering of gene expression profile of naive CD4⁺ T cells from cord blood, peripheral blood, fetal mesenteric lymph nodes and 2 months after CBT and BMT. Naive cord blood CD4⁺ T cells have a distinct transcription profile to naive peripheral blood CD4⁺ T cells, but similar to fetal T cells. Cord blood T cells during early reconstitution after CBT retain the fetal-like transcription profile, and thus recapitulate fetal ontogeny. (C) Two-dimensional principal component analysis showing a relationship among naive CD4⁺ T cells from cord blood, peripheral blood, and fetal mesenteric lymph nodes, and 2 months after CBT and BMT, vs T-regulatory cells from fetal mesenteric lymph nodes and peripheral blood. T cells segregate based on developmental stage and T-cell type. Thus, confirming the distinct transcription profile of naive CD4⁺ T cells after CBT is not a result of adoption of T-regulatory function.