Immunological abnormalities in BXSB mice at the onset of SLE development

Male BXSB mice develop murine lupus spontaneously at about 3 months of age. Polyclonal B-cell activation is thought to play a major role in the development of the syndrome in these mice, but the immunological events which lead to this activation are not known. We therefore examined the immune characteristics of mice aged 10-16 weeks, at the onset of disease. We found several immunological markers, indicating polyclonal B-cell activation leading to early, preclinical, disease activity in both male and female BXSB mice, but consistent abnormalities in the percentages and function of lymphocyte subpopulations were found only in male BXSB mice. In particular, the ratio of helper to suppressor/cytotoxic T cells was found to be significantly lower in male BXSB, than in either females of this strain, or normal control DBA2 mice. We conclude that defective immunoregulation is likely to be significant in the initiation of murine lupus, since it is detectable at the onset of disease in male BXSB mice.