A reappraisal of the relationship between subepidermal immunoglobulin deposits and DNA antibodies in systemic lupus erythematosus: a study using the Crithidia luciliae immunofluorescence anti-DNA assay.

The relationship between normal skin subepidermal Ig deposits (subepi. Ig) and disease activity in systemic lupus erythematosus (SLE) is controversial. For this reason we have compared certain qualitative and semiquantitative aspects of subepi. Ig in skin biopsies from uninvolved flexor forearm skin to an objective measure of disease severity in SLE, i.e., serum antibodies to double stranded DNA (anti-dsDNA) as determined by the Crithidia luciliae indirect immunofluorescence assay. We have found that both the number of subepi. Ig classes present and the subepi. Ig fluorescence intensity correlate positively with the presence and amount of circulating anti-dsDNA. The group of patients with subepi. IgM alone had anti-dsDNA no more frequently than the group without subepi. Ig; whereas, the group who concurrently had subepi. IgG, IgA, and IgM frequently had high titers of anti-dsDNA. There were some exceptions to these findings in individual patients, however. These findings illustrate the importance of carefully defining the immunofluorescence findings in SLE normal skin.