Modulation of Ro/SS-A autoantigens in epidermal keratinocytes has been implicated in the pathogenesis of photosensitive forms of Ro/SS-A-antibody-associated cutaneous lupus erythematosus (LE) such as subacute cutaneous LE and neonatal LE. Since Ro/SS-A ribonucleoprotein particles have recently been shown to be very complex molecular structures, we have performed studies to determine whether the expression of three of the Ro/SS-A antigenic polypeptides might be differentially regulated in transformed human epidermal keratinocytes following UVB radiation. Our findings indicate that both total cellular and cell surface levels of calreticulin are upregulated by UVB exposure more so than are either the 52- or 60-kD Ro/SS-A antigens. These results suggest that calreticulin could be a critical component of the Ro/SS-A ribonucleoprotein complex involved in the pathogenesis of Ro/SS-A-antibody-associated LE skin lesions.