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) d evelop 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 o f the 52-kd SS-A/Ro, 60-kd SS-A/Ro, and 48-kd SS-B/La antigens in normal su n-protected and sun-exposed skin in 14 patients with LE with photosensitivi ty, 12 patients with LE without photosensitivity, and 4 normal individuals. The presence of circulating antibodies to these antigens was measured in a ll 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 tha n in those patients with LE without photosensitivity (P<.001). Antigen expr ession was highly correlated with the presence and titer of circulating ant i-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 bot h 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. Thu s, the expression of these antigens in keratinocytes may be an important de terminant of the development of both SS-A/Ro and SS-B/La autoantibodies and of photosensitive forms of LE.