Ultraviolet B irradiation and cytomegalovirus infection synergize to induce the cell surface expression of 52-kD/Ro antigen

Cultured human fibroblasts (MRC-5) have been previously demonstrated to express calreticulin, but not Ro autoantigen, on their surface after human cytomegalovirus (CMV) infection. The present study addresses the question of whether other stimuli, alone or in combination with CMV, can induce the surface expression of Ro autoantigens on human fibroblasts. Using a fixed-cell ELISA to detect autoantigen expression, a synergistic effect between ultraviolet B (UVB) exposure and CMV infection on the surface expression of 52-kD/Ro antigen, but not 60-kD/Ro or calreticulin, was observed. The enhanced expression of 52-kD/Ro antigen was significant and specific, compared with untreated cells, cells infected with CMV alone or irradiated with UVB only, and cells subjected to other treatments, such as low pH. Immunofluorescence studies confirmed these findings and indicated that cells expressed 52-kD/Ro protein on their surface at 24h after a combined UVB and CMV treatment. These studies provide evidence that synergy between UVB irradiation and CMV infection may play a role in the induction of cell surface expression of the human autoantigen, 52-kD/Ro.