Cultured murine dermal cells can function like thymic nurse cells.

We have established a dermal fibroblast-like stromal cell line, DFB-1, and a clone, 12E2, from epidermal sheets prepared from the skin of BALB/c mouse ears by trypsin digestion. They were suggested to be fibroblasts or myofibroblasts, as 1) they were polygonal or spindle-shaped under the phase-contrast microscope, 2) they did not possess any tonofilaments or desmosomes, and 3) they did not express any marker for bone marrow-derived cells or macrophages. Interestingly, these cells showed a unique phenomenon of "pseudo-emperiporesis," which was first recognized in the interaction between thymic nurse cells and thymocytes. Namely, two T-cell clones and one T-cell hybridoma migrated beneath the cytoplasmic projections of the fibroblast-like cutaneous stromal cells in culture. Furthermore, secretion of interleukin 7 by these cells was confirmed by bioassay using an IL-7-dependent cell line and by inhibition with anti-interleukin 7 antibody, and the expression of interleukin 7 mRNA was also demonstrated in these cells by a combination of reverse-transcriptase polymerase chain reaction and Southern blot analysis. These data strongly suggest the presence of unique stromal cells even in the skin, probably at the upper dermis, which can function like the nurse cells in the thymus. These stromal cells may play a crucial role in cutaneous immunophysiology.