High Treg development in the first year of life gives insight into immune regulation

Results We show that upon activation, CB cells easily adopt a Treg phenotype, whereas Th17 cells can not be induced. Although production of inflammatory cytokines is dramatically lower in CB cells, addition of Th17 inducing cytokines IL-1b or IL-6 did not influence this phenomenon. Instead, an increased programmed death (PD)-1 signaling and decreased Th17 defining transcription factor RORC activation underlie the prevention of inflammatory T cell activity. The propensity for Treg development is a phenomenon which we still observed in samples from 12 month old children, whereas we found Th17 cell development as early as three months after birth. This development in the first year of life is likely related to prevention of aberrant T cell responses towards self and the developing microbiome. Conclusion These data give more insight into the development of the immune system and inflammation and can lead to novel targets in JIA therapy, aiming at the balance between Treg and Th17 cells.