Frequency and phenotypic feature of autoantibody-producing cell precursors in the preclinical stage of murine lupus.

The present study addresses the question of whether there is a difference in the frequencies of autoantibody-producing B-cell precursors in healthy compared with lupus-prone mouse strains. Spleen mononuclear cells (MNC) from 4-week-old (i.e. at the preclinical stage of lupus) mice were activated in vitro for 3 and 6 days with lipopolysaccharides (LPS) and the numbers of IgG, IgA and IgM autoantibody-producing cells were analysed by the ELISPOT assay. The results indicate a high frequency of IgM autoantibody-secreting cells after both 3 and 6 days in vitro stimulation. In spite of high frequencies of IgG-producing cells appearing late during the course of LPS stimulation, no IgG or IgA autoantibody producing cells were detected. No significant differences in the autoantibody repertoire were noted between healthy and lupus-prone mice, indicating that independent of the genetic background the immune system has the capacity to react with autoantibody production. Phenotypic analysis of LPS-induced, IgM-secreting B cells showed clearly that the majority of them were surface IgM+, CD5+ but Thy-1-.