Estradiol Enhances Binding to Cultured Human Keratinocytes of Antibodies Specific for SS-A/Ro and SS-B/La. Another Possible Mechanism for Estradiol Influence of Lupus Erythematosus

A strong association between anti-SS-A/Ro and anti-SS-B/La antibodies and skin lesions has been well documented in subacute cutaneous lupus erythematosus and neonatal lupus erythematosis in which 70 to 80% of patients are female. In order to better understand the mechanisms of the influence of sex hormones on cutaneous lupus, we designed immunopathological in vitro experiments to evaluate the effects of estradiol and other sex steroids on the binding of SS-A/Ro- and SS-B/La-specific antibodies to cultured human keratinocytes from neonates. Cultured human keratinocytes incubated with antisera specific for SS-A/Ro or SS-B/La Ag were fixed with either acetone or paraformaldehyde and then analyzed in indirect immunofluorescent assays or by FACS analysis to detect cell surface IgG binding as an indirect measure of SS-A/Ro and SS-B/La Ag expression on the cell surface of keratinocytes. Estradiol (10(-5) to 10(-7) M) augmented binding of antiserum probes on the surface of cultured keratinocytes, with 10(-7) M estradiol showing the highest induction of cell surface binding of antisera specific for SS-A/Ro plus SS-B/La Ag (24.5% of cells were positive). In contrast, dihydrotestosterone, testosterone, and progesterone showed no augmentation. The augmentation by estradiol was partially inhibited by the antiestrogen nafoxidine. Estradiol augmented the relative incidence and absolute number of small or cuboidal cells binding antibodies specific for SS-A/Ro and SS-B/La Ag, whereas the number and incidence of larger differentiated cells binding anti-SS-A/Ro and anti-SS-B/La decreased significantly in cell cultures stimulated with estradiol. Flow cytometric analysis utilizing monospecific anti-SS-A/Ro or anti-SS-B/La sera showed that estradiol induced binding of anti-SS-A/Ro in 13.1% of cultured keratinocytes, of anti-SS-A/La in 14.4%, and of sera specific for both Ag in 21.4%. This direct association between estradiol and the augmentation of binding to the cell surface of human keratinocytes of IgG from antisera specific for SS-A/Ro and SS-B/La Ag may be a trigger factor of immunologic damage in lupus and may be important in the different sex rates observed in skin manifestation of subacute cutaneous and neonatal lupus erythematosis.