UVB IRRADIATION DECREASES THE MAGNITUDE OF THE TH1 RESPONSE TO HAPTENBUT DOES NOT INCREASE THE TH2 RESPONSE

Exposure of murine skin to low doses of ultraviolet-B (UVB) radiation before sensitization with hapten reduces the ability of antigen presen ting cells (APC) in the draining lymph nodes to initiate contact hyper sensitivity responses in vivo and results in the induction of hapten-s pecific suppressor T cells. In the present study, we tested the hypoth esis that exposure of skin to UVB radiation suppresses T cell response s to hapten in vivo by altering the functions of APC, resulting in dec reased stimulation of Th1 lymphocytes, which mediate contact hypersens itivity responses, and preferential activation of Th2 cells. C3H/HeN m ice were exposed to either a single 2 kJ/m(2) dose of UVB or to 400 J/ m(2) of UVB daily from FS40 sunlamps for four consecutive days and sen sitized with fluorescein isothiocyanate on UV-irradiated skin. Drainin g lymph node cells were collected 18 h after sensitization and co-cult ured with nylon wool-purified T cells from naive or fluorescein-immuni zed mice. Unseparated lymph node cells or sorter-purified fluorescein- bearing APC from UV-irradiated mice induced less T cell proliferation than APC from non-UV-exposed mice. Lymph node cells produced less Th1 and Th2-associated cytokines, interferon-gamma and interleukin-4, resp ectively, in response to APC from UV-irradiated animals compared with APC from unirradiated, fluorescein-sensitized mice. Thus, low doses of UV radiation do not result in preferential stimulation of Th2 respons e in lymph nodes, and results from cloned cell lines may incompletely reflect T cell responses in vivo.