Developing Human Fetal Skin Demonstrates a Unique Lymphocyte Signature

The study utilized mass and flow cytometry to investigate early human skin immunity, revealing a unique lymphocyte signature in fetal skin. Most conventional αβ T cells in fetal skin exhibited a naïve, proliferative phenotype, but some CD4+ and CD8+ cells showed memory-like features and a tendency for IFNγ production. Regulatory T cells (Tregs) accumulated dynamically during the second trimester, correlating with hair follicle development, and displayed an effector memory phenotype distinct from adult Tregs. These findings highlighted prenatal skin lymphocyte characteristics that could impact understanding of antigen and allergen exposure in utero and infancy.