Non-Cytoxicity of “Nuclear Antibodies” from Lupus Erythematosus Sera in Tissue Culture

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Abstract
The localization of binding sites of antibodies in sera from systemic lupus erythematosus (SLE) patients was determined by indirect immunofluorescent techniques and compared with the locus of binding of specially-prepared FL cell antisera on both living and dead tissue culture cells. Anti-FL cell antibodies uniformly localized peripherally, involving only the cell membrane and cytoplasm of both viable and non-viable cells. SLE sera bound with the nucleus of non-viable cells only. The failure of the SLE serum to react with viable cells was further studied by morphological examination of cells stained with hematoxylin and eosin which had been previously exposed to SLE and FL cell rabbit antisera. Viable tissue culture cells exposed to SLE antibodies were identical with normal controls, indicating that there was no cytotoxicity associated with the SLE sera. Finally, SLE serum cytotoxicity was evaluated by incubating freshly trypsinized FL cells in tubes with a series of different sera, with and without complement. After 72 hours, these cells were evaluated as to their degree of attachment and subsequent growth on the tube surface. SLE antibodies were non-toxic to these tissue culture cells. In contrast, anti-FL cell antibodies displayed marked cytotoxicity both on the slides and in tubes, especially in the presence of complement. These results demonstrate that anti-nuclear factors in SLE serum do not damage human amnion cells in tissue cultures. The inference is drawn that these factors cannot be implicated in the direct pathogenesis of SLE.