Expression of SS-A/Ro and SS-B/La antigens in skin biopsy specimens of patients with photosensitive forms of lupus erythematosus.

CONTEXT The reason that only some patients with lupus erythematosus (LE) develop autoantibodies to SS-A/Ro and SS-B/La antigens and photosensitivity is unknown. One hypothesis is that both events are related to the level of expression of these antigens in the skin. OBJECTIVE AND DESIGN To test this hypothesis, we measured the expression of the 52-kd SS-A/Ro, 60-kd SS-A/Ro, and 48-kd SS-B/La antigens in normal sun-protected and sun-exposed skin in 14 patients with LE with photosensitivity, 12 patients with LE without photosensitivity, and 4 normal individuals. The presence of circulating antibodies to these antigens was measured in all patients. SETTING Outpatient clinic in an academic medical center. RESULTS We found that the expression of the 52-kd SS-A/Ro, 60-kd SS-A/Ro, and 48-kd SS-B/La antigens in skin biopsy specimens obtained from the same site was 4- to 10-fold higher in patients with LE with photosensitivity than in those patients with LE without photosensitivity (P<.001). Antigen expression was highly correlated with the presence and titer of circulating anti-SS-A/Ro and anti-SS-B/La antibodies (P<.001). CONCLUSIONS These findings indicate that photosensitivity and the presence and titer of circulating anti-SS-A/Ro and anti-SS-B/La antibodies are both directly correlated with the expression of accessible and immunoreactive SS-A/Ro and SS-B/La antigens in the skin specimens of patients with LE. Thus, the expression of these antigens in keratinocytes may be an important determinant of the development of both SS-A/Ro and SS-B/La autoantibodies and of photosensitive forms of LE.