The frequency and function of regulatory T cell and pDC in newborns

Objective The aim of this study was to study on the frequency and function of CD4+ CD25+ CD127low regulatory T cells and pDC from neonatal umbilical cord blood. Methods Umbilicus cord blood of neonates who were born to HBV DNA negative(<100IU/ml) mothers and peripheral blood of normal adults were collected.The frequencies of pDC and the expression levels of CD80/CD83/CD86/TLR-9 on pDC were detected by flow cytometry and analyzed using FlowJo software. The frequency of CD4+ CD25+ CD127lowTreg were detected by flow cytometry and analyzed using FlowJo software. The level of IFN-γ, IFN-α, IL-6, IL-10, IL-17A and Flt-3L in whole blood of two groups were detected by Luminex technology and FLEXMAP 3D analyzer.Two groups of samples were compared with Mann-Whitney test and t test. Results With the frequency of CD4+ CD25+ CD127lowTreg cells there was no significant difference between neonates (7.34±1.54) and adults (8.14±1.15), (t=-1.40, P=0.144). The frequency of Lin1- HLA-DR+ CD123+ pDC of neonate (0.07±0.04) was significantly lower than the normal adult group(0.14±0.04, P=0.000). The positive expression rate of pDC surface molecules CD80, CD83 and CD86were significantly lower than those of normal adult(P=0.000). The positive rate of TLR-9 was no significant difference between neonates(21.30±22.50)and adults(34.27±11.31), (t=-1.26, P=0.220). The level of IFN-γ and IL-17A in the neonatal group were significantly lower than that in adult group(P=0.003, P=0.010), but there was no statistically significant difference between the two groups in the content of IFN-α, IL-10, IL-6 and Flt-3L. Conculsions In the newborn pDC reduce the frequency, immature phenotype and lack of stimulate capacity may be associated with chronic infection of the newborn after HBVinfection, while Treg cells may be independent of the mechanism. Key words: Regulatory T cells; cytokines; Dendritic cells; Hepatitis B virus; Newborn