Adult human skin is home to huge numbers of T cells that as pivotal part of the immune system fulfill important roles in immune surveillance and play a key role in cutaneous immunity. T cells are already present in fetal skin, yet their function remains elusive. The aim of this study is to delineate the nature and significance of fetal skin T cells and to compare it with T cells in adult skin. As T cells are extremely rare in fetal skin we compared established and novel isolation techniques and succeeded to enrich them in sufficient numbers to better characterize them. The highest T cell yield was achieved with an automatic tissue dissociator in combination with an appropriate dissociation kit. This methodology preserved surface markers such as CD4, CD8, CD45RA and CD45RO upon single cell isolation. Flow cytometry analysis showed that prenatal CD3+ T cells were predominantly positive for CD4 and that higher CD8+ T cell percentages were found in fetal compared to adult skin. Further examination showed that most of the fetal skin T cells had a naive phenotype, while adult T cells largely expressed a memory phenotype. Moreover, we were able to expand sizable numbers of fetal T cells in vitro, using different culture conditions, which principally preserved the phenotype before culture. These studies will expand our understanding of the formation of important prerequisites for a functional skin immune system and consequently help to better understand many human skin diseases characterized by T cell activation and proliferation.

Isolation and characterization of T cells from human prenatal skin