Loss of self-tolerance to single-stranded deoxyribonucleic acid (sDNA) in vitro.

The spleens of many normal and autoimmune-susceptible strains of mice mount a specific, IgM, anti-sDNA plaque-forming cell (PFC) response in vitro in the absence of an exogenous source of antigen. This response was not related solely to levels of xenotropic or ecotropic virus and was generated from a small number of precursor cells capable of binding sDNA. Small numbers of anti-sDNA PFC were also apparent in serum-free medium and the response of low-responder strains could be augmented with pokeweed mitogen. T cells and macrophages were not essential and cell division was required early in culture to obtain a peak response on day 5. These results suggest that autoantigen-sensitive cells may escape normal regulatory mechanisms in vitro and differentiate into clones of autoantibody secreting cells.