Interleukin 2 is a proliferative signal for B cells from autoimmune mice

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Abstract
T cells from murine lupus strains manifest complex defects in interleukin 2 (IL 2) production and receptor expression. The capacity of B cells from such mice to utilize IL2 as a growth factor has not been previously reported and is examined herein. Anti-Thy-1.2 plus complement-treated spleen cells from 6–8-week-old autoimmune MRL- Ipr/lprmice and from age and sex-matched immunologically normal CBA/J mice were cultured with lipopolysaccharide (LPS) for 36 h and analyzed for the expression of IL 2 receptors using the monoclonal antibody 7D4. The percentage of B cells expressing IL2 receptors was comparable in MRL-lpr/lpr and CBA/J mice. In contrast to those from CBA/J, BALB/c and (BALB/c × NZW)F1 mice, LPS-stimulated B cells from MRL-lpr/lpr and from (NZB × NZW)F1 mice were capable of proliferating in response to IL 2. Fractionation of MKL-lprl/lprB cells using Percoll gradient density separation demonstrated that the IL2-responsive population consisted predominantly of large cells. In addition, unfractionated B cells from MRL-lpr/lpr mice were found to be substantially more responsive to IL2 than those from CBA/J and BALB/c mice following activation with anti-immunoglobulin plus LPS. The hyper-responsiveness to IL 2 may be a consequence of the state of activation of autoimmune B cells and is of potential importance in the pathogenesis of systemic lupus erythematosus.