Clinical and experimental immunology 2017 07 05() doi 10.1111/cei.13008
Regulatory T cells (Tregs) control immune responses by suppressing various inflammatory cells. Tregs in newborn babies may play an important role in preventing excessive immune responses during their environmental change. We examined the number and phenotype of Tregs during the neonatal period in 49 newborn babies. Tregs were characterized by flow cytometry using cord blood (CB) and peripheral blood (PB) from the early (7-8 days after birth) and late (2-4 weeks after birth) neonatal periods. CD4(+) Foxp3(+) T cells were classified into resting Tregs (CD45RA(+) Foxp3(low) ), activated Tregs (CD45RA(-) Foxp3(high) ), and newly activated T cells (CD45RA(-) Foxp3(low) ). Compared with CB and PB in the late neonatal period, the percentage of Tregs and all Treg subpopulations in the CD4(+) lymphocyte population were significantly increased in the early neonatal period. Furthermore, the proportion and absolute number of activated Tregs were markedly increased compared with other Treg subpopulations, such as resting Tregs and newly activated T cells (non-Tregs), in the early neonatal period. Increased Tregs concomitantly expressed the suppressive molecule CTLA-4. The upregulated expression of CCR4 and downregulated expression of CCR7 were also observed in expanded Tregs. When cord blood cells were cultured in vitro with CD3 mAb for 5 days, CD4(+) CD45RA(-) Foxp3(high) cells were significantly increased during the culture. Thus, the presence of increased activated Tregs in early neonates may play an important role in immunological regulation by suppressing excessive T cell activation caused by the immediate exposure to ubiquitous antigens after birth. This article is protected by copyright. All rights reserved.