Premature birth and cesarean section affect neonatal CD4+ T cell gene expression and cellular function

Premature birth and cesarean section are major perinatal factors influencing immune development and are associated with increased morbidity and inflammatory diseases. However, their impact on neonatal adaptive immunity remains incompletely understood. To determine how gestational age and mode of delivery shape early immune programming, we analyzed CD4⁺ T cells, central regulators of adaptive responses, from preterm neonates (28–36 wga) and full-term neonates delivered by cesarean section or natural birth. We performed transcriptomic profiling by mRNA sequencing, complemented by functional assessment of T cell activation, proliferation, and cytokine production following stimulation. The mode of delivery exerted a dominant effect on the CD4⁺ T cell transcriptome and function. CD4⁺ T cells from full-term neonates delivered by natural birth exhibited an immune activation signature compared with those from cesarean section and produced higher levels of multiple cytokines, but showed reduced proliferative capacity. In contrast, prematurity induced modest changes in basal gene expression relative to full-term cesarean section neonates. Despite these limited transcriptional differences, CD4⁺ Tcells from preterm neonates displayed enhanced proliferation and increased secretion of inflammatory cytokines IL-13, TNFα, IL-6, and IL-17F, indicating heightened responsiveness. Collectively, our findings suggest that CD4⁺ T cell immune programming begins in utero, as preterm neonates exhibit heightened inflammatory responsiveness. At term, the mode of delivery further refines this developmental trajectory. Cesarean section is associated with a restrained functional profile, whereas natural birth induces an immune activation signature and enhanced cytokine production. These results provide functional evidence that neonatal CD4⁺ T cell trajectories are established during fetal life and subsequently modulated at birth, underscoring the layered influence of perinatal factors on immune development.