Thy-1+ dendritic cells in murine epidermis are bone marrow-derived.

Area of Science:

• Immunology
• Dermatology
• Cell Biology

Background:

• Thy-1+, Ly-5+ dendritic cells are a newly identified resident cell population in the murine epidermis.
• The origin (ontogeny) and function of these epidermal dendritic cells remain unknown.

Purpose of the Study:

• To investigate the origin and turnover of epidermal Thy-1+ cells.
• To determine if these cells are derived from bone marrow or related to peripheral T-lymphocytes.

Main Methods:

• Utilized chimeric mice created by reconstituting lethally x-irradiated mice with allogeneic bone marrow cells.
• Employed immunofluorescence staining to analyze the density and repopulation of Thy-1+ cells in epidermal sheets.
• Varied the number of donor bone marrow cells and included thymocytes to assess repopulation enhancement.

Main Results:

• X-irradiation substantially reduced the density of indigenous Thy-1+ epidermal cells.
• Allogeneic Thy-1+ dendritic epidermal cells repopulated the epidermis slowly, starting at 5-7 weeks post-irradiation.
• Repopulation was not significantly enhanced by increasing bone marrow cell numbers or adding thymocytes.
• No epidermal repopulation by Thy-1+ cells was observed when syngeneic bone marrow cells were used.

Conclusions:

• Epidermal Thy-1+ dendritic cells are derived from the bone marrow.
• These cells are suggested to be distinct from conventional peripheral T-lymphocytes.