Cells with UV-specific DNA damage are present in murine lymph nodes after in vivo UV irradiation

Ultraviolet radiation is absorbed in the skin, especially in the epidermis. After ultraviolet irradiation the number of major histocompatibility complex class II+, adenosine triphosphatase+ Langerhans cells and Thy-1+ dendritic epidermal cells in the epidermis decreases. Whether this decrease is due to migration of these cells or to loss of membrane markers is not clear. To address this question we have used the monoclonal antibody H3 directed against cyclobutyl thymine dimers-a form of DNA damage that is specifically induced by ultraviolet radiation-to investigate whether H3+ cells are present in the draining lymph nodes of the skin after ultraviolet irradiation of hairless, inbred mice (HRA/Skh). After a single dose of ultraviolet radiation (Westinghouse FS40, 1.5 kJ/m2), H3+ cells were present in the paracortex of the draining lymph nodes. No positive cells were found in the blood of irradiated mice. These results suggest that the H3+ cells in the lymph nodes originate from the skin. The number of H3+ cells in the draining lymph nodes increased the first 24 h after irradiation and then stabilized. Immunohistochemical double staining revealed that all H3+ cells were major histocompatibility complex II+, and that only a fraction of the cells were NLDC-145 positive. No V gamma 3 T-cell receptor bearing cells could be found in the lymph nodes after UV irradiation of the skin.