Mycobacterium bovis bacillus Calmette-Guerin treated human cord blood monocyte-derived dendritic cells polarize naïve T cells into a tolerogenic phenotype in newborns

Background: As one of the first infectious challenges of life, the impact of neonatal Mycobacterium bovis bacillus Calmette-Guerin (BCG) vaccination on the polarization of neonatal T helper subset has not been well defined. Methods: We investigated the effect of BCG-treated cord blood (CB) dendritic cells (DCs) on naïve CD4+ T cells polarization compared with that of adult blood DCs. Results: BCG-treated CB DCs had significantly lower expression of CD83 and a higher ratio of CD47/Fas than BCG-treated adult blood DCs. BCG induced significantly lower IL-12 but relatively higher IL-10 production from CB DCs than adult blood DCs. Moreover, in comparison with BCG-treated adult blood DCs, BCG-treated CB DCs induced higher IL-10 production and cytotoxic T-lymphocyte antigen 4 (CTLA-4) expression, and lower interferon-gamma (IFN-γ) production from naïve CD4+ T cells. On the other hand, lipopolysaccharide- treated CB DCs had similar capacity as prime naïve CD4+ T cells did to produce higher IFN-γ, lower IL-10 production, and CTLA-4 expression compared with their adult counterparts. Conclusion: These results suggested that BCG-treated CB DCs might be semi-mature DCs which polarize naïve T cells into a tolerogenic T cell phenotype in newborns.